Solex 30 Pict 1 Adjustment? Best 51 Answer

question

What do I do if I have overhauled my carburetor and my VW Beetle won’t start anymore?

alejandro community answer

Make sure your accelerator pump is working, if there is an adjustment adjust it so that a good strong jet comes out. Make sure your air bypass valve has power and look for leaks at the inlet gasket. You may even have your float set too low. Make sure it’s at the top of the bowl, usually a thin copper washer under the float valve. Yes, you’ll probably need to take it off and take it apart, it’s easier on a bench. Check the volume screw (small) is about 2 1/2 turns out and the large screw bypass screw about 1 1/2 turns. put it back on It could be a lot of things since I didn’t even mention the choke or the vacuum leak. But make sure she squirts in the first place. If you still can’t find the problem, take it to a mechanic.

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Tuning a carburetor to provide an engine with the correct jetted air/fuel mixture has always been a task nearly impossible for most hot rod owners and tuners. In the past, most performance engine tuners would inspect the spark plug, exhaust port, and the first 6 inches of the header for the correct color and then make a guess as to what nozzle size change was required. One of the disadvantages of this method is that the header and spark plug can only show what the mixture was like at the exact RPM and load condition at which the plug check was done, so you had to mostly just tune by trial and error.

Now a new, more scientifically advanced way of checking the air/fuel mixture is to use an infrared exhaust analyzer and/or an extended range oxygen sensor in the exhaust system; Now the fuel mixture can be read at any desired speed and load condition. The content of the engine exhaust can be read to show what the air/fuel mixture is at any speed or load and how efficiently the engine is burning the fuel.

Proper tuning of any engine can mean the difference between an engine that runs well and one that always sounds and runs like it needs tuning. For most hot rodders, one of the biggest mysteries is how to jet the engine to get the proper air/fuel ratio your performance engine needs to deliver not only rideable horsepower when you want to go fast, but the engine with the right air-fuel mixture for driving in heavy traffic or cruising on the motorway.

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If the air/fuel mixture is too rich for the engine while cruising, the engine may have a tendency to overload and foul the spark plugs, while too lean an air/fuel mixture may cause misfires at idle at low loads or tend to overheat or overheat. Proper air/fuel mixture for all driving conditions will allow you to get all the horsepower out of the engine while allowing as many miles as possible on one tank of fuel without overheating or causing engine damage from too lean air. fuel mixture.

Recent advances in exhaust gas analysis technology and extended range oxygen sensor technology have made it possible to read and/or record the actual air/fuel mixture under almost all driving conditions. In the past, exhaust gas analyzers tended to be large and expensive, but the new devices on the market are not only compact and portable, but also affordable.

Performance and replacement carburetors sold today are generic tuned or jetted unless the carburetor is built for a specific engine package and fuel. A carburetor that is not built and tuned for a specific engine, exhaust system, and fuel should provide an air/fuel mixture that is rich enough for a wide range of engines (but this is not always the case). If the carburetor delivers an air/fuel mixture that is too lean, the engine will run sluggishly, overheat, or the lean mixture can cause engine damage. If the carburetor delivers an air-fuel mixture that is too rich, the engine can have a tendency to overload, foul the spark plugs, run sluggishly and suffer from a lack of power.

Proper carburetor selection can make the task of fine tuning the air/fuel mixture easier, my preferred replacement carburetors are: for a mild engine a Quadrajet, Edelbrock Thunder or Performer of 650cfm or smaller, for a high performance engine I prefer Barry Grant’s powerful Demon carburetor Inc. or the Holley 4150 hp, on a supercharged engine, forced draft carburetors available from Barry Grant have given us excellent results.

The fuel you use (pump or race), air density (i.e. altitude, barometric pressure, air temperature, humidity), compression ratio, camshaft, exhaust system, ignition timing curve, engine condition, fuel pressure, airflow through the air filter, etc .affect the carburetor adjustment required to obtain the correct fuel mixture for your engine.

The first task is to get the correct spark advance curve for the engine and fuel used, then the fuel pressure must be checked to ensure it has the correct system pressure at all engine load conditions. If the fuel pressure drops below the correct pressure, the carburetor air/fuel mixture will become lean, which can result in engine damage. After confirming that the spark advance curve is correct, many of the problems we see can be traced back to the fuel mixture not being suitable for the needs of the engine.

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Ignition timing and ignition curve Before checking the air-fuel mixture, the ignition timing and ignition curve must be correct. Regardless of which ignition system you use, if the spark timing does not match the engine’s requirements, the engine will not produce all of the potential horsepower that is built into it. With any distributor, power replacement or original equipment, the mechanical and vacuum advance curves must be verified and then adjusted to the engine and fuel used. (Note: MSD manifolds come with a very conservative mechanical advance curve and come with the bushings and springs to get the desired curve).

Barry Grant Inc. has a very good reference for recommended initial timing using camshaft duration at 0.050 valve lift which I find very useful, just go to the Barry Grant website and click on the demon selection guide. The advance curve we see most often on a 9:1 compression, mild cam Chevrolet V-8 engine is 12 degrees of initial timing plus an additional 24 degrees of mechanical advance at 3,600 rpm. If vacuum advance is used, it should they will provide a MAXIMUM of 10 degrees of EXTRA advance at engine vacuum over 12 inches! An engine equipped with a hot cam or air gap/race intake manifold may respond well to 18 degrees of initial timing combined with a shorter 18 degree mechanical advance curve at 3,200-3,400 rpm.

If the engine is not spark advanced enough it can lack power, have poor throttle response, consume too much fuel and cause the engine to overheat, while if the engine is spark advanced too much it can cause the engine to lose power lack, ping, consume too much fuel or let the engine overheat.

Proper ignition timing produces maximum cylinder pressure at about 12 degrees after the piston passes top dead center. Only then can you get all the energy out of the fuel and achieve maximum performance and engine efficiency. There are two methods we use to check the distributor’s advance curve. The best method involves using a manifold dynamometer to test and adjust both the mechanical and vacuum advance curves and the second choice is to use a recall advance timing light to check the advance curves while the engine is running at various engine speeds and negative pressure conditions running.

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Air/Fuel Mixture Reading A lean fuel mixture (insufficient fuel for the amount of air in the cylinder) can cause an engine to jerk or skip at idle and part throttle, stumble under acceleration, cause the engine to overheat and cause a lack of power, and cause possible engine failure due to the lean air/fuel mixture. A rich fuel mixture (too much fuel for the amount of air in the cylinder) can cause an engine to rev up when idling, fouling the spark plugs and also leading to lack of power or sluggish running. There are several methods to determine if the air/fuel mixture is correct, including the following:

1. Reading the spark plugs with a lighted magnifying glass. In this method, the base of the spark plug insulator (white portion of the plug) is inspected for slight discoloration of the insulator just above where the insulator comes through the steel case. If the mixture is too lean, it won’t leave any color, while a rich mixture will cause the fuel ring to be more prominent. Mixtures that are too rich give the spark plug a sooty appearance.

Stripping the manifold and looking at the color of the exhaust port in the cylinder head and the first 6 inches of the exhaust manifold is also used to determine the air/fuel mixture, but the color of the manifold and spark plug can only show how the air/ fuel mixture was at the load condition at which you performed the check.

In the days of leaded fuel and spot ignition this method worked well but today the use of unleaded fuel and high energy ignition systems has made this method much more difficult as there is very little color to be seen on the spark plug making it a job for an expert. Examining the spark plug insulator for signs of knocking, seen as aluminum spots, can be an effective way to determine if the ignition timing is too advanced for the octane rating of the fuel being used.

2. The second method is to use timed acceleration runs or maximum speeds for the propulsion system. This involves using trial and error jet changes to get the best results. It’s not that easy to get the right mixture for cruise (that’s the air/fuel mixture that the engine will operate on under light load conditions, such as z and faults, to get the best engine drivability.

When adjusting the Power and Cruise mixtures, it is always advisable to stay slightly rich to avoid engine damage. The idle mixture is adjusted with a tachometer to get the maximum RPM from each idle screw and then leaner to get a 20 RPM drop in speed. This is known as the lean drop method.

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3. The easiest and most accurate method we have found is to use an infrared emissions analyzer. This type of device allows us to determine the air-fuel mixture by reading the exhaust gases. By using an infrared emissions analyzer, the carburetor jetting curve (air/fuel mixture) can be checked at idle, cruising or power loads and then tailored to what your engine needs to perform optimally under all racing/driving conditions to run. A high NOx reading from the exhaust gas analyzer can be used as a method to determine if ignition timing is too early and creating excessive heat in a cylinder’s combustion chamber.

4. An optional method of checking air/fuel mixtures is to use a broadband oxygen sensor installed in the exhaust manifold. The sensor is read with a digital air/fuel gauge, the device that I have had the best results with is available motorsport refresh. In this method, the air/fuel mixture is determined by looking at the oxygen/unburned fuels in the engine exhaust; Readings can be very accurate, but false readings can be produced by an exhaust leak, engine misfires, or a high overlap camshaft at lower speeds (these false readings are caused by the oxygen sensor incorrectly measuring the extra oxygen in the exhaust due to the misfire). exhaust leak or high overlap cam)

Jetting with an Infrared Gas Analyzer or Broadband Oxygen Sensor The most accurate and easiest way to check an engine’s jetting (air/fuel mixture) is to observe the CO reading from an infrared gas analyzer and/or broadband oxygen sensor . First insert the sample probe into the tailpipe, and then the device will read the exhaust and provide the readings needed to determine the air/fuel mixture. The method of infrared exhaust gas analyzer and/or broadband lambda sensor allows checking the part load air-fuel mixture, which is otherwise almost impossible, the readings of both methods can be read in real time or recorded and later replayed. It is important to note that all changes other than jetting changes and other basic adjustments should be made by an experienced carburetor professional.

A starting point for air/fuel mixtures for most racing engines is: Idle: 1 to 3 percent CO or an air/fuel mixture of 14.1-13.4:1 Cruising: 1 to 3 percent CO or an air/fuel -Mixture of 14.2-14.0:1 fuel mixture Performance mixture and acceleration: 6.6 percent CO or a 12.0:1 air/fuel mixture for a normal engine; A high-performance engine with an improved combustion chamber design, such as a Pro Stock or a Winston Cup engine, will use a slightly leaner power mixture with 4 percent CO or an air/fuel ratio of 13.0:1 in some cases.

Adjusting the Air/Fuel Mixture Using an Infrared Exhaust Gas Analyzer An infrared exhaust gas analyzer reading indicates air/fuel ratio, engine misfire, engine combustion efficiency, and excessive combustion chamber heat (detonation) by looking at the CO exhaust. The reading of an infrared gas analyzer is the reading we use to determine the air to fuel ratio. (Note: CO is partially burned fuel.)

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The other readings that exhaust gas analyzers provide are: HC (Hydrocarbons): The amount of unburned fuel or an indicator of engine misfire, the best mixture gives the lowest HC.

CO2: The product of complete combustion, the best mixture gives the highest CO2 value

O2: A high O2 value indicates a lean mixture; an exhaust leak or the engine has a hot cam. Note: If O2 is above 2-3%, CO readings may not be accurate.

NOx (nitrogen oxides): A gas produced by excessive heat in the combustion chamber. In many cases, a high reading can be related to excessive ignition timing causing detonation that can lead to engine damage.

The best power and air/fuel mixture (CO) will burn all the oxygen in the cylinder and produce the least amount of engine misfire (HC). The ideal air/fuel mixture for any engine speed and load condition will also cause the engine efficiency (CO2) to be at its highest.

Tuning with a Digital Air/Fuel Gauge The digital air/fuel gauge method with an extended range oxygen sensor requires you to know what air/fuel mixture your engine requires for each driving condition. This data should be available from your engine builder or you can use an infrared exhaust gas analyzer which will help you determine what air/fuel mixture your engine needs to run at its best. The air/fuel measurement method uses a broadband oxygen sensor to determine the fuel mixture by analyzing the unburned fuels in the exhaust.

An extended range oxygen sensor can read air/fuel ratios of up to 9 to 1, or on the lean side air/fuel ratios of 19 to 1 or leaner (a standard oxygen sensor is only accurate at air/fuel ratios of about 14.7 to 1). This method has the advantage of extremely fast response times for the readings, but may be less accurate on an engine with a racing camshaft or supercharger application under light load/low speed test conditions due to the excessive oxygen in the exhaust generated by the cam overlap or the Supercharger blow-through effect at low engine speeds and low load conditions.

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The Innovate Motorsports Digital Air/Fuel Gauge allows you to sample air/fuel mixture data at a rate of 12 samples per second for up to 44 minutes, recording the ideal air/fuel mixture curve that gives you the infrared Exhaust gas analyzer can support the determination. While using an infrared exhaust gas analyzer has a slower response time, the advantage is that it not only measures the oxygen/unburned fuel content in the exhaust, but also allows you to determine the air/fuel mixture by measuring the CO -observe value; the misfire rate of the engine can be determined by observing the HC reading; Engine efficiency can be determined by observing the CO2 reading, and knock caused by excessively advanced ignition timing can be detected by observing the NOx reading.

In-Vehicle Testing After confirming that the basic engine condition and setting (fuel pressure, control curve, etc.) fuel mixture is idle to 3,000 rpm. If the cruise mixture is off, first swap out the nozzles to get the correct air/fuel -Mixture in the range of 2,500 to 3,000 rpm in cruise flight. Then check and adjust the idle mixture. If the air/fuel mixture is too lean at idle or part throttle and the idle mixture screws do not have enough adjustment, correction may include increasing the size of the idle jet.

If the mixture is still lean at 1,000-1,800 rpm, a carburettor such as e.g. B. a Quadrajet or Edelbrock of the Performer or Thunder series, the idle port throttle may need to be enlarged so that more fuel can be pumped at part load. This lean condition at part load will cause the engine to skip or stall, this is due to the lean air/fuel mixture, this problem is very common on many of the performance carburetors sold today. If the air/fuel mixture is too rich at idle and part throttle, the idle jet/restriction may be too large and may need to be replaced with a smaller one.

The next step is a road test using a handheld infrared emissions analyzer and/or a broadband oxygen sensor to check the main air/fuel mixture jets at cruising speed, followed by a load air/fuel mixture check. During a road test you can read the air/fuel ratio and then correct it to get it right at idle, cruising/easy throttle and full power.

Tuning The Carburetor A carburetor has an accelerator pump, idle, main jets and in most cases a drive system designed to provide the correct air/fuel mixture for the needs of the engine. An idle system has an idle jet/throttle that must be modified to deliver the desired fuel mixture for the needs of the engine at idle and off-idle. On a power valve carburetor, the size of the main jet determines the air/fuel mixture that is delivered to the engine at light loads/cruising speeds (1,500 rpm and above). The power valve restriction (below the power valve) is the determining factor for the air/fuel mixture that the carburetor delivers when the power valve is open; A 6.5-inch power valve is open, providing the richer air/fuel mixture needed at high power demands when the vacuum is below its 6.5 opening point.

A carburetor that uses metering rods in the primary jets, such as A Quadrajet or the Edelbrock Performer/Thunder series uses the metering rods to change the air/fuel ratio for both the engine’s performance and cruise mixture requirements. The larger the diameter of the metering rod, the leaner the air/fuel mixture becomes. The accelerator pump system adds fuel as the throttles are opened, adjusting the injection volume and duration of the accelerator pump tuning is done primarily through trial and error.

For a Demon/Holley style carburetor, the most common combination used is a .031″ squirt along with a pink pump cam. We frequently modify the accelerator pump duration spring on Demon/Holley style carburetors and Edelbrock Performer/AFB carburetors to make the pump more active and help eliminate lag issues during acceleration. The chart above shows the gases in the exhaust that an infrared exhaust analyzer reads and how the gases change as the air/fuel mixture changes.

If you are purchasing an engine package that has been tuned or developed on a dynamometer and is running on an engine dyno, it is a good idea to have the engine manufacturer tell you the initial ignition timing and ignition timing curve that they recommend for your engine and also find out which air/fuel mixture they recommend for the engine at both maximum power and cruising rpm loads, and then make sure they match the engine in the vehicle. If the engine builder is running the engine on the dyno, if possible have them use an air/fuel gauge such as the Innovate Motorsports unit and you can then use the recorded data to tune the fuel curve to run the engine with the same air /fuel mixture that the engine builder used on the test bench.

Many of the engine packages that we checked for spark timing and air/fuel ratio curves had the correct spark timing and air/fuel mixtures for high rpm/full throttle operation, but require a lot of tuning work at low rpm/part throttle /normal driving conditions. In most cases, when an engine is run on an engine dyno, they only test maximum power while using race-style headers with an open exhaust, and they supply the engine with outside air to a carburetor without an air filter.

The air/fuel mixture and ignition timing curves should be corrected for the real operating conditions of your car’s engine compartment, where the hot air from the radiator and exhaust system is produced along with the changes in exhaust back pressure created by the manifolds and mufflers you are using can result in the engine not operating at the same performance as seen on the dyno.

TheSamba.com Forums Forums Index -> Beetle – Late Model/Super – 1968 On -> HELP! Beetle Running Strange Backfiring View original topic: HELP! Beetle Running Strange- Backfiring dr8699 Wed Jan 14, 2015 9:05 am Need some help to get to the bottom of my problem.

last work – petrol tank cleaned (rust free!) new fuel lines filter

new plugs/cables, adjusted points and valves and new carburetor. ran strong for a while at average temperatures

When it was hot outside the bug got vapor lock so I replaced the fuel lines and filters and moved them to a cooler area. I also installed an electric fuel pump.

The bug was running great until rust clogged my fuel filter – under the tank in front of the pump. I cleaned the tank and filter from rust and now it doesn’t run properly. I played with the mixture a bit before concluding that it was all clogged. So I cleaned the tank/lines/filter and now I’m getting misfires

it starts and drives fine for a few minutes.. drive it around the naborhood and it starts a faint backfiring roar/thud in the exhaust, not really loud but once it starts the drivability goes down the shit.

It fails when I take off from a station – it totally drains power and I have to change the throttle clutch and keep the revs high so it doesn’t cut out. After this one starts and I park it, it doesn’t want to idle for long and will eventually get stuck and fail.

my thought condensation? Water or ice in my intake manifold messing up the A/F mixture? Gas does not vaporize in the manifold and then burn up in the exhaust?

It’s like 10-20 degrees outside and my bug has no heat lines.

76 Beetle with 74 carburetor engine – 34 pict3 carburetor

dr8699 Wed Jan 14, 2015 9:08 am after this happened it’s really hard to get it to start again, I end up hitting the gas a few times when I start it and it slowly comes to life . It only keeps running if I give it enough gas to keep the revs high

Volks Wagen Wed 01/14/2015 09:09 Have you checked timing, valves and points?

Volks Wagen Wed Jan 14, 2015 9:14 am You can put your hand on the manifold under the carb and see if it’s really cold next time and that would help check for carb/manifold icing. Do you have the original air filter and exhaust? You need heat for the manifold…

B52Gunner Wed Jan 14 2015 9:36 AM sounds like a timing issue.

dr8699 Wed Jan 14, 2015 10:04 am I have aftermarket air filters and the previous owner capped the heat pipes

I doubt timing is the issue because I had a mate when I got it about a month ago and it ran like a top at low mid and high rpm…then the fuel line got clogged, I took some light ones Carburetor adjustments before + and – a half turn or full turn to see if that was a problem. now I’m backfiring…never backfired before with the timing set

The only thing that has changed since the last time it ran like a champ was the slight carb adjustment, fuel filter and WEATHER

So I tend to ice or too cold for gas to vaporize in the ice cold manifold and when the unburned fuel gets into the warm/hot exhaust it vaporizes and burns????

dr8699 Wednesday 14 Jan 2015 10:11 am

my setup – first attempt at uploading a picture.. keep your fingers crossed

Volks Wagen Wed Jan 14, 2015 10:40 am Right – good Exhaust misfire is fuel burning in a hot pipe there. I have a question – your manifold has 2 vacuum lines? where are they going?

Q-Dog Wed Jan 14, 2015 10:52 am They don’t have any manifold heat at all. I would suspect that this is a significant part of your problem. I bet the carburetor could use a little tidying up and possibly a little choke adjustment. You can get it to work, but without carb heat you’ll never get it to run well in temperatures below about 60F.

dr8699 Wed Jan 14, 2015 12:06 pm I already have a new carb in there.

The stock carburetor had 3 vacuum ports – 2 to the manifold vacuum and one to the air cleaner

The new carburetor had 2 vacuum ports, I assumed one is to the manifold and the other to the air filter but I couldn’t get confirmation so I blocked both of them

My Dist uses double vacuum advance – when I connected the hoses to the NEW carb it didn’t run soooo. I blocked BOTH vacuums on the manifold and ran it like a 009. My timing buddy set the timing and preroll (I don’t know the timing and don’t have a gun)

He adjusted the advance and then said test it…come back adjust it a little then test it…repeat until it was smooth at low mid and high rpm…it ran almost perfectly, until I got constipated again

Volks Wagen Wed 1/14/2015 12:58 PM OK – so you need to check a few things…

1. Make sure all connector cables are in the correct order

2. Make sure that all candles are lit (if not, the fuel-air mixture is not burned but thrown into the exhaust and if hot = misfire)

3. Hang the number on the mailing list (usually hard to reach since it’s on the back – take a picture or use a girly makeup mirror)

4. Make sure your distributor doesn’t move (tighten tightly in both directions – shouldn’t be any movement)

5. Adjust your valves

I could be wrong but here’s what I’m thinking… You’re getting fuel in the exhaust because…

a) It does not burn in all cylinders because there is no spark anywhere

b) it does not fully burn due to weak ignition spark or improper ignition timing

c) The mixture is too rich and not all of the fuel burns

d) a valve remains slightly open and the air/fuel partially flows through the combustion chamber from inlet to outlet…

dr8699 Wed Jan 14, 2015 13:27 pm a) it doesn’t burn in all cylinders because there is no spark somewhere -> it doesn’t fire – runs smooth on first start and idles quietly (if I didn’t get spark, would it be wrong and fiddly if started first AND after warm right?)

b) It doesn’t fully burn due to a weak spark or improper ignition timing -> MIGHT be a weak spark I suppose

c) The mixture is too rich and not all the fuel is burning -> quite possible as I was tinkering with A/F prior to this misfire problem

d) a valve stays slightly open and the air/fuel partially flows through the combustion chamber from inlet to outlet -> valves were adjusted less than 200 miles ago when I replaced the plugs and wires (I also adjusted the points)

Does this scenario sound logical to you guys/gals? hot engine under the intake manifold heats the manifold pipe while I drive … then the car is parked in the cold (while I clean the tank for a few days) … condensation forms in the pipe

that moisture is frozen in the manifold, that cold ice prevents the gas from evaporating … OR …

I start the bug and it runs fine for a few minutes with the choke on, then the ice starts to melt and starts diluting my gas or A/F mixture? That moisture that a wet blanket puts on my spark/ignition/combustion?

dr8699 Wed Jan 14, 2015 1:29 pm the unvaporized gas (in the liquid state) gets warmed up somewhere else (not in the intake manifold because it’s freezing cold), then warms up, then vaporizes and burns in the exhaust?

Volks Wagen Wed Jan 14, 2015 2:43 pm dr8699 wrote: The unvaporized gas (in the liquid state) is warmed up somewhere else (not in the intake manifold because it’s freezing cold) but warms up, vaporizes and then burns in the exhaust?

This liquid fuel would find its way into the cylinders/combustion chambers and be difficult to burn completely and likely get something out of the exhaust.

If you had water in the intake the same would happen = it would go away and you would get white smoke out the exhaust for a while.

So you’re saying the manifold stays ice cold after driving the car for about 20 minutes? If it does, then it’s a manifold glaze and you need to add heat to the carburetor and manifold. You can do this by supplying warm air to the carburetor or heat to the manifold. VW did both! You should try to find a way!

morymob Thu Jan 15, 2015 6:13 am Air filter 4 Winter must go, look for an original air filter or at least one with the large heat pipe from rt cyl (#3) to get the afilter

heat for carbohydrate absorption. Need the ‘stovepipe’ curved Lg pipe fitting that goes down curves to fit against #3cyl. No heated inlet really adds to the icing situation. If you can get heat to the intake you might be able to overcome enough to run decently. Those dopy shiny air filters aren’t your best bet, get dirty quickly and tend to cause a richer fuel mixture, kind of like a partially closed choke, my 2cts were down that road.

Jarmchairpilot Thu Jan 15, 2015 7:36 am Backfire in VW Bug Engine is usually caused by lean air/fuel mixture.

The reasons for this fall into three main causes – either

1. Air escapes before the fuel/air mixture reaches the cylinder head combustion chamber, or

2. the carbohydrates. is not adjusted to provide enough fuel to air ratio to ignite efficiently in your engine.

3. Ignition timing, spark gap, point gap or valve lifter must be properly adjusted.

It is safest to check everything in the correct order as per the manual.

Use only high-quality, German VW and Bosch parts as much as possible. Try Wolfsburg West and GeneBerg.com.

Aftermarket carburetor, exhaust and ignition parts DO NOT OFFER THE FAMOUS RELIABILITY OF O.G. Volkswagen!

To get you back on the road quickly, you can slightly enrich the mixture at the carburetor by unscrewing the volume control screw counterclockwise 1/4 to 1/2 turn. This is the bottom small screw of two-crew Solex carb-like my 30-pict3.

Replace all gaskets, especially the carburetor to manifold and carefully check that the rubber boots on the manifold are tight.

VERTED71 Sa Jan 17, 2015 10:49 am B52Gunner wrote: sounds like a timing issue.

x2! My distributor clamp was loose and moving left or right due to engine vibration. Check your time and adjust the valves….oh yeah, look for exhaust leaks.

ashman40 Sa Jan 17, 2015 7:04 pm dr8699 wrote: Does this scenario sound logical to you guys/gals? Hot engine under the intake manifold heats up the manifold pipe as I drive…

The reason VW had the heat risers running from the exhaust and then down the bottom of the intake manifold is because the engine case does NOT transfer enough heat to the manifold by convection to allow the fuel in the air in the intake manifold to flow.

The air/fuel mixture flowing through the intake noticeably reduces the available heat, making the interior colder. Because of this, when outside temperatures are well above freezing, ice can form at the inlet. This lower intake temperature and pressure when the engine is running causes the fuel to condense from the air-fuel mixture.

dr8699 wrote: Then the car is parked in the cold (while I clean the tank for a couple of days)… Condensation forms in the pipe

that moisture freezes in the manifold, that cold ice prevents the gas from evaporating…

Water condensation forms on the warm side of surfaces when the air has the same pressure and humidity on both sides. Therefore, on cold days, moisture forms on the INSIDE of the window. For water/ice to form on the inside of the intake, it would need to be warmer on the inside of the intake than on the outside. Because of this, the first thing that comes out of the exhaust on a cold morning is white smoke. Moisture in the exhaust condenses because the inside of the exhaust is warmer than the outside.

I don’t think ice in the intake will happen with your setup.

It’s likely that the fuel (not water) is condensing out of the air/fuel mixture because your intake isn’t heated. Liquid fuel in the intake tract can get into the exhaust because it does not burn as a liquid. It is pumped into the exhaust, where it ignites when hot gases from another cylinder heat it. There must be air (oxygen) in the exhaust for it to burn. This can come from a cylinder not firing, or more likely an exhaust leak.

All of this becomes even more pronounced in colder weather.

Check your spark plugs. If any are dirty, they can allow unburned air-fuel into the exhaust system where it ignites and causes a misfire. But in the end it sounds like the weather has changed and your lack of intake heat is now causing problems.

volksnhousin Sun Jan 18 2015 6:22 am Remove, clean and install the idle jet on your carburetor. (if you haven’t already done so)

Also check the electric fuel shutoff nozzle/solenoid valve on the carburetor…Turn on the key, remove the wire and reinstall. If it clicks well. If it doesn’t click, it’s dead and may be your problem.

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“Hey, how hard can that be? Just turn the screw and you’re done, right?”

There’s a lot more to learn about adjusting the idle mixture than just turning a few screws and slamming the hood shut. You’ll be amazed at how much better your street engine will run with a properly adjusted idle mixture. The idle circuit is a critical component to overall road engine operation and proper idle mixture adjustment goes a long way to improving throttle response, fuel economy and emissions.

Now that we have pointed out the importance of adjusting the idle mixture, take a moment to read the sidebar (“Circuit City”) to better understand how the idle shift works. Before we get started, it’s best to do the actual tuning outdoors as the engine will idle for a long time. Never work on a running engine in a closed garage unless the exhaust fumes are properly routed outside with exhaust hoses. You’ll also need a couple of small, straight screwdrivers; a low-speed tachometer; and a vacuum gauge. Make sure the transmission is in park if it’s an automatic transmission, or in neutral if it’s a manual transmission. Lock a tire or set the parking brake to keep the car from rolling.

First, make sure the engine is at operating temperature and the choke is completely turned off. A cold engine requires more fuel than a fully warm engine, even with the choke turned off. Remove the air filter and connect the tachometer to the engine. Typically, one lead is connected to the negative side of the coil and the other to a suitable ground. Connect the vacuum gauge so that it shows the intake manifold vacuum.

Remember that working near the engine is very dangerous and can chew fingers, snag wires from the tachometer or check engine light, and generally cause havoc if you’re not careful. Always work slowly and deliberately when tuning a running engine. Rushing to the hospital for sewing takes all the fun out of working on cars.

Before starting the engine, slowly turn each idle mixture screw in fully and count the number of turns required. Do this for each idle mixture screw and then return them to their original position. If all idle mixture screws are not set equal, do so now. Remember to always adjust both screws equally. This helps to even out the idle mixture and keep the engine running as smoothly as possible. If the carburetor is new to the engine, start at 1 turn out (counterclockwise) from full in.

Now start the engine and set the idle speed to approx. 850 rpm with the idle screw. If your engine has a big cam and needs to idle at a higher RPM, that’s fine. Note the reading on the vacuum gauge. Next, turn an idle mixture screw and read the change on the vacuum gauge. As the vacuum reading increases – say from 14 inches to 14 inches – move to the other side of the carburetor and turn the mixture screw in as well. Also note the reading of the vacuum gauge here; If the gauge continues to rise, adjust each idle mixture screw an additional -turn. On most carburetors, turning the mixture screw in (clockwise) leans the mixture, while turning it counterclockwise (out) enriches the mixture.

If the engine sputters or the vacuum drops when turning in the mixture screw, first unscrew both screws by about one turn and evaluate the result. The aim of adjusting the idle mixture screws is to achieve the highest possible idle vacuum at a set idle speed. If the idle speed increases after adjusting the idle mixture screws (which it probably is), be sure to adjust the idle speed back to base speed. This is important as higher idle speed will increase the vacuum reading. Maintaining a default idle speed makes it easier to evaluate changes to the idle mixture screws.

The best way to accurately set the idle mixture is to use an emissions tester to read the hydrocarbon (HC) and carbon monoxide (CO) levels. As you move the idle mixture screws you will see some very dramatic changes in HC and CO readings. The ideal idle mixture setting minimizes both HC and CO levels. HC readings are expressed in parts per million (ppm), while CO is expressed as a percentage. A fact that is generally overlooked is that CO can be equated with air/fuel ratio. For example, 0.01 percent CO corresponds to an air/fuel ratio of 14.7:1 and 0.38 percent corresponds to an air/fuel ratio of 13:1.

Most four-barrel carburetors use two screws to adjust the idle mixture. Some newer Holley and All-Demon carburetors use four idle mixture adjustment points. The idle mixture procedure is exactly the same for these carburetors, except now you are adjusting four adjustment points instead of two. Again, an important key to determining the ideal idle mixture is an accurate balance of all four of these mixture settings.

This procedure also works on engines with lumpy camshafts. A potential pitfall is that large cams often idle at vacuum levels below 8 inches. These engines also require large throttle openings to let air in to allow the engine to idle. This exposes the idle transmission slot, which can cause off-idle tripping issues. The only way to spot this problem is to remove the carburetor and see if the throttle bodies expose more than .040 inch of the idle transfer slot (you can measure this with a spark plug gap wire gauge). If too much of the slot is uncovered, the best solution is to drill a 1/16″ hole in the leading edge side of the throttle body and increase the size in 1/32″ increments if needed. This allows more air past the throttle bodies, allowing the throttle body to close slightly, leaving the transfer slot just barely uncovered by the throttle body. Be careful not to drill these holes too large, otherwise the throttle bodies will have to be fully closed to produce the correct idle speed. Unfortunately, this can also result in a flat spot off idle.

This article was co-authored by Hovig Manouchekian. Hovig Manouchekian is a car repair and design specialist and manager of Funk Brothers Auto, a family business established in 1925. With over 30 years of experience in the automotive industry, Hovig specializes in the process of car repair and maintenance. He is also very knowledgeable in general automotive issues and needs including engine repair, battery replacement and windshield accessories and maintenance. Hovig’s knowledge and hard work have helped Funk Brothers Auto win Angie’s List Super Service Award five years in a row. This article has been viewed 1,050,080 times.

Article overview

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Before you adjust your carburetor, make sure you remove your car’s air filter so you can access the carburetor. Then start your car and let it warm up. When it’s up to operating temperature, you’ll find the 2 screws on your carburetor that adjust the air and fuel mixture. You can then use a screwdriver to turn both screws a quarter turn at a time until your motor purrs evenly. To set your idle speed, locate the idle mixture screw, which limits fuel flow at idle. Do no more than half a turn clockwise and adjust just until your engine idles smoothly. To learn how to tell if your engine is running too lean or too rich and how to correct it, read on!

What is a Solex carburetor?

The Solex carburetor was invented by Marcel Mennesson and Maurice Goddard, the founders of the Solex company. Solex carburetors, widely used by many European manufacturers, are also used in passenger and commercial vehicles. The Solex carburetor is a modification of an ordinary carburetor.

The ordinary carburetor works well under normal working conditions, but does not work well under conditions such as winter and summer seasons, idling conditions and high acceleration conditions. In these situations, the Solex carburetor works well.

The main function of carburetors is to create the correct ratio of air and fuel. The Solex carburettor engine is known for its easy starting and superior engine performance. The Solex carburetor is a downdraft carburetor. With a downdraft carburettor, the air enters at the top and exits at the bottom.

The main disadvantage of the simple carburetor is that it cannot maintain different air-fuel mixtures for different driving conditions, but the Solex carburetor can provide different mixtures for different driving conditions. This variation in air-fuel mixture for different conditions can be achieved with a Solex carburetor.

This Solex carburetor can provide rich engine starting and lean mixture when driving the vehicle at economical speed. It can also provide different mixtures for different situations like engine idling, low speed operation, acceleration, etc.

Structure of the Solex carburetor:

In the Solex carburetor, the fuel chamber is the part that collects fuel from the fuel tank and stores it in the carburetor to form an air-fuel mixture. This fuel chamber has a float that is used to maintain the fuel level in the fuel chamber. There is a main line through which the fuel venturi reaches the throat tube. Fuel enters the venturi throat from the main jet, located at the end of the main pipe. When the choke is opened, the fuel evaporates from the main jet.

Fuel from the main jet is mixed with air that comes in when the choke is opened to form an air/fuel mixture, and this air/fuel mixture reaches the engine cylinder when the throttle valve is opened. Apart from the main jet, there are three other tubes that supply fuel to the engine cylinders; They are pilot jets, pump jets and launch routes.

The pump jet receives fuel from the accelerator pump and the pilot jet receives fuel from the main jet. The pilot jet pipeline is separate from the main line. The accelerator pump works with an accelerator pedal. These accelerator pumps are used during acceleration.

The pilot nozzle is used in idle or no-load condition. It has a pilot vent that allows the pilot jet to form an air-fuel mixture. Near the end of the idle position line is an idol screw that is used to control the amount of air/fuel mixture that is sent into the engine cylinder.

The starting gear gets its fuel from the starting circuit or starter motor. These starting circuits are used to supply the air-fuel mixture during the start-up period. This initial circuit consists of a flat disk with holes of varying radius used to control fuel delivery during takeoff.

This starting circuit also has an air venturi that supplies air to the starting circuit to create an air-fuel mixture. The air-fuel mixture from the starting circuit is supplied to the engine cylinder from the starting passage located below the throttle valve.

Function of Solex carburetor:

In front of the fuel chamber, the fuel enters the fuel chamber, which is blocked by floats when the required amount of fuel enters the fuel chamber. The float blocking the passage of the fuel tank and fuel chamber raises the fuel level in the fuel chamber and blocks the passage when the fuel level reaches the maximum level in the fuel chamber.

#1. Working at the time of beginning

When starting, the engine needs a rich mixture. The Solex carburetor is a starting circuit or bi-starter to provide a rich mixture at startup.

The main function of the by-starter is to compensate for the problem that occurs when starting the engine, especially in the winter season.

This gives the engine a rich mixture when starting. The ratio of a rich mixture of air and fuel is 11:1, where 11 parts is air and 1 part is fuel. Typically, the fuel ratio expected from the engine is 15:1, but at start-up time, a ratio of 11:1 is required. This bi-starter has a flat disc and holes with different diameters.

The starter fuel jet and the starter air jet are connected near the hole in the disc, and the air-fuel mixture reaches the engine on the suction stroke through the various holes in the starter disc.

Fuel and air flow from the bi-starter to the engine through these holes. This disc can be turned manually using a starter lever, allowing it to be adjusted according to fuel and air requirements. For example, a larger hole in the disc would be used in winter because more fuel would be needed to start the engine in winter.

#2. Working with the engine idling and running slowly

Idle is a situation where the vehicle engine is running but not at vehicle speed. This condition usually occurs when the red light turns the vehicle off and the engine turns on. In the idling condition, the engine is unloaded, but all engine friction must be removed to keep the engines running.

During the idle or low speed condition, the throttle is fully closed. Because the throttle is closed, the suction created by the suction stroke acts directly on the pilot nozzle. A pilot jet is a jet that gets its fuel from the main. The pilot jet tubes are connected to the main line and supply it with fuel.

At idle, the throttle valve closes and sufficient pressure is not generated to draw fuel from the main jet. The intake stroke of the engine thus sucks the air-fuel mixture directly out of the pilot nozzle. The fuel from the pilot nozzle is incorporated and mixed with the air drawn in from the external environment by the pilot air bleed air.

The enriched mixture from the pilot jet is fed directly to the engine via a pipe under the throttle valve.

There is a useless screw near the opening of the pilot jet to control the engine speed by controlling the amount of air-fuel mixture going to the engine.

Bypass arrangements are also provided directly above the throttle valve so that when the pressure is close enough to the throttle valve, the air-fuel mixture is drawn out of the passage arrangement. The throttle opens slightly when this close arrangement is used.

The bypass arrangement provides a less enriched air-fuel mixture, allowing the engine to run smoothly with full movement of the air-fuel mixture. The idle position operates at a speed of 0 to 30 (KMPH) and then stops automatically.

#3. Working during acceleration

When accelerating, there is a load on the engine. The engine requires additional air-fuel mixing during acceleration to give the engine proper acceleration. An additional accelerator pump injector is provided to the right of the float chamber to provide the additional air/fuel mixture required during acceleration.

An additional nozzle is provided above the main nozzle to supply the additional fuel supplied using the accelerator pump. This accelerator pump is a diaphragm pump connected to a pedal. It is also connected to the throttle body via an accelerator pedal linkage.

When we press the gas pedal, the accelerator pump works and at the same time the throttle valve opens at the same time. As soon as the accelerator pedals are pressed, the accelerator pump works and delivers additional fuel through the additional nozzle.

When the accelerator pedals are released, the accelerator pump draws fuel from the fuel chamber and stores it to provide additional fuel for the next acceleration.

Types of Solex carburetors:

Solex carburetors are divided into three main categories.

after his way

The bore of the throttle chamber u

According to his example.

The Solex carburetor is classified according to the direction of flow through the carburetor.

Upgradable carburetor.

Horizontal carburetor.

downdraft carburetor.

Depending on the design of the induction system

Single carburetor for single intake manifold.

Dual port carburettor for two intake manifolds.

Compound carburettor with two connections for the single intake manifold.

Selection of Solex carburetors:

#1. The direction of the airflow

If you want to replace an old carburetor with a new one, this can be done simply by determining the type of flange on the carburetor. Downdraft carburetors are often used in modern vehicles because they are easily accessible from all sides.

Horizontal carburetors are used in sports cars and racing cars. Rising-draft carburetors are used for engines where fuel is supplied.

#2. The number of the carburetor

Typically this is determined by the engine type, whether one or more carburetors are used. Typically, more than one carburetor is used in sports cars and racing cars. The purpose of using multiple carburetors is to reduce the length of the intake manifold. And above all, the reduction of bends that impede the free passage of the air-fuel mixture.

Advantages of the Solex carburetor:

The automatic choke regulates the air/fuel mixture during engine start. It creates a richer fuel-air mixture when the engine is cold and then gradually makes the fuel mixture leaner as the engine warms up. This is achieved by a butterfly valve in the throat of the carburetor at the very top. When this valve is closed, airflow is greatly reduced and the fuel/air mixture is rich. When the valve is open, airflow is maximized and the fuel/air mixture should be correct for a warm engine.