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Ron Watson

Mis-fire / dead cylinder

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When I bought this car it mis-fired, idled rough, popped and back fired. I knew it needed some tuning, but it sounded good otherwise. It has never run properly and I can't seem to sort it out. Engine is a 2332cc.

 

I started with rebuilding the carbs (dual weber 44 IDF's). It ran better, but still popping and back firing at low speed.

Tired different pilot jets (currently has 60's) fuel screws are at about 2 turns out.

 

However, #3 cylinder does not respond to the fuel screw. I can turn it all the way in or take it out, with no response.

 

Also, if I pull the plug wire off #3, there is no change in the idle, like a dead cylinder.

 

When I rev the engine running I can see fuel in the #3 carb barrel, but when I pull the #3 wire at the cap,

the spark is very weak. (CDI ignition, not sure of what kind).

 

I have not checked the valves yet or done a compression check.

 

Thanks for any help.

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Look into that weak spark issue first. Compare the spark to a known good cylinder. Possibly a bad distributor cap or wire. 

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I have already installed new plugs and wires, cap and rotor look new.

Does anyone know if a CDI ignition can fail on one cylinder?

I always thought you either get spark or you don't, but that's been my experience on single cylinder 2 stroke motorcycles.

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I've seen many new caps be bad, usually cheap Auto Zone stuff. You'll need to figure out why that spark is weak. Swap wires with another cylinder just to rule that out. 

 

Are we talking VW here? I'm not very familiar with that ignition, but yes it usually works or doesn't. 

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You can adjust the valves on that motor in under 30min. Pushrods are prob chromo on that engine so just set the lifters to 0. :thumb:

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Is the exhaust tube on that cylinder hot to the touch? 

Pull the plug and rest it on the exhaust and see if it is indeed getting spark all the way to the plug.

Is fuel getting to the cylinder.

Accelerator pump working?

Check the inside of the cap for carbon tracks or cracks.

With the motor running, spray carb cleaner along the sides of the carb and see if the idle changes- if yes- you have a leak at a gasket.

Swap plug wires and see if the dead cylinder changes.

Clogged jets, suckers get clogged easily.

 

Look into a velocity stack air meter- it is crucial in setting the jets and getting all 4 cylinders balanced.

 

Just a few things I can think of that plagued me when I had my VW motor back in the day.

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Thanks for all the suggestions and input.

I had been swapping idle jets, thinking that was the problem, so I'm sure they're clear.

It's getting a weak spark on #3 and that's the dead cylinder. I can not get the carb to respond to the fuel screw, but I do see the accelerator pump squirt.

I don't have any spare "known good" parts, so I bought a (same as I have) 009 ignition kit with a new coil and plug wires. Should be here in the next day or two.

It looks pretty clean around the base of the intakes, but I will check for leaks.

I did the carbs when I initially got the car, so I think there clean, but that will be next, if the new ignition doesn't fix things. BTW, I have a snail type sinc tool for balancing the carbs.

As lousy as it runs, it's got some pretty serious horsepower (VW 2332cc with dual 44 webers). But I'm not going through a lot of money at it though.

I'm hoping to do a V6 Honda swap, after I finish some honey do's.

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I had a similar issue on a 2054 of mine, what it ended up being was I had a cap from a non doghouse style engine where the oil cooler is in the fan shroud not on the outside, on the older style caps there a built in retard to prevent cylinder number 3 from building excess heat where has the air that cools the cylinder has to pass thru the oil cooler first, I did almost everything you talked about, but a new cap solved my issue

Edited by Stormin189
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You don't need new parts to diagnose this.  you have 1 bad cylinder- so move a plug wire from another cylinder to the #3 position and put #3 where you took that wire from.  If the problem moves away from #3 to another hole- BINGO!

 

Remember this- Keep it simple, Start in one direction and and work forward/backwards. Don't jump around or you might miss the problem.  Sounds like the Fuel system is ok, work on the electric side.  Check the cap/rotor, if thats good, move to the wires. If they are good, go to the plugs. Throw in a new set just for added cheap security. 

 

VW's are such a simple motor, I have rebuilt them in my bedroom when I lived at home. Picked the damn thing up out of my 63 and walked it into the house. LOL

 

And as Stormin189 said- #3 is a culprit for less air flow. My sand rail had major overkill for my oil system. Deep Sump + stock oil cooler and a 96 plate cooler with oil filter inline. I had over 6 quarts of oil in my motor. 

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