Stumped, motor won't fire on #1 Options

[Rusty]

We're stumped. I even caved and took it to my local VW expert for help.

Background: The car had been stored for 7-8 years. Before storage, it had been worked on by a third party (including replacing the distrubutor, IIRC). When the car was stored, it was running poorly.

Symptom: Car won't fire on cylinder #1, but fires fine on 2 thru 4. (Was it firing on #1 prior to storage... I dunno. I stored it out of frustration.)

Motor: 1973 1.7L, dual Weber carbs, Pertronix points replacement in 009 distributor.

Details: Car has air, fuel, and spark.

Air: Valves are adjusted correctly (.006) and timing is on. Compression on all cylinders is 90-95 pounds. Heat exchanger removed and checked for obstruction. Covering/blocking the air intake on #1 has no effect to the motor running.

Fuel: Carb on cylinders 1/2 has been cleaned and adjusted. We can watch fuel go into the cylinder. Some of it ends up as white smoke going out the exhaust. There is an oil leak on the drivers side of the motor and the oil smells faintly of fuel.

Spark: Plug wires are routed correctly. Taking a plug out and laying it on engine tin, spark is strong. Wires, cap, rotor, and plugs have all been swapped out. Pulling the plug wire on #1 at any RPM results in no change.



I talked to my guy today... he's very well regarded in the area. He's as stumped as I am.

Any thoughts?

[Rusty]

I picked up the car today and discussed some of the above theories with my mechanic. He's very gracious and only charged me for a fraction of the time he has in the car.

We talked about cleaning the carb (he tore it all the way down & cleaned) and also swapping the jet stacks (also tried). I think these potential solutions can be ruled out.

Have you checked the airflow into each cylinder using a sync meter? This will let you know that each cylinder is pulling the same volume of air. Even by putting your hand over the opening of the carb you should be able to feel the vacuum.

Yes. In kg/hr on my meter at approx 1000 rpm idle: #1 - 6, #2 - 8, #3 - 7, #4 - 7.

I'm know expert but I had a similar condition that turned out to be a dropped a Valve Seat?

Also, was a Cam for Carburetor conversion from FI made. Might cause for a rough running engine condition. Did it run right before you put it in storage?

Damn, I hope it's not a dropped valve. It doesn't sound like that to me.

I have no idea what cam is in the engine. It's not the original engine to the car, so it's anyone's guess. It ran well for me at one time - I'll leave it at that.

I too suspect a fuel delivery problem for that barrel. Look down the throat of #1 carb barrel, you should see fuel squirting when you open the throttle enough to actuate the accel pump. Spraying some fuel down the barrel (with spray bottle in a leather gloved hand, and fire extinguisher within reach) will tell you if you have a fuel delivery problem.

Could also be a valve problem, if so, probably intake, such as stuck valve, bad rocker arm, bad lobe on cam. This could be seen by taking off the valve cover and turning the engine.

First thing I'd do is warm it up and block the throttle at about 1800 rpm's and squirt some fuel down #1 barrel. Just be really careful. In theory you could use ether, but that's not good on your engine.

You can look down the carb and see fuel squirting.

My guy tried both fuel and ether. With the exchanger removed, he sprayed fuel directly up into the chamber trying to get something to ignite.

I'm starting to wonder if the cylinder has too much fuel or isn't mixing well enough with the air.

If it's always cyl#1, at least you have narrowed it down some.

If compression is good, it can only be fuel or ignition. If the plug fires when grounded to the tin, it's a good sign, but harder to test once installed in the engine.

I test them using the magnetic pick-up of a strobe type timing light or an inductive spark checker along the plug wire (the in-line spark checkers would accomplish the same thing). That insures that the circuit is complete and the plug has a decent ground. If spark is good it really points toward fuel. If it does not spark when the plug is screwed into the head, it may not be grounded well or at all, or could be a bad plug.

Test one thing at a time and you will figure it out.

Thanks for the encouragement, man. (IMG:style_emoticons/default/smile.gif)

Maybe try swapping #1 plug with another cylinder plug. See if problem moves with the plug.

Good idea. When this was done, the issue stayed with cylinder, not the plug or plug wire.

The leak at the head cylinder mating surface of #1 is unusual to me. The oil leaking there smells like fuel. I'd think that area was compromised except the compression came out to 90 pounds on #1.

Strange indeed. I'll be able to piddle with it in the evenings a bit.

Appreciate all the commentary. I've got a lot to think about and I need to do it methodically.

[iankarr]

Have you checked the airflow into each cylinder using a sync meter? This will let you know that each cylinder is pulling the same volume of air. Even by putting your hand over the opening of the carb you should be able to feel the vacuum.

Yes. In kg/hr on my meter at approx 1000 rpm idle: #1 - 6, #2 - 8, #3 - 7, #4 - 7.

Interesting that the side with the unequal readings is the one with the issue. I had a very similar condition on my carb car (only in my case it was #2 that didn't seem to be firing) and once I got the airflow dialed in and equal, the problem went away. I wonder if adjusting the air mixture screw on #1 (and balancing the stacks) might bring #1 back to life. It's also possible that the higher vacuum on #2 is somehow stealing juice from its neighbor.