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?

check to see if the cap is secure on the distributer and the firing order. put a test plug on the wire and see if it sparking or replace the wire with a known good one from a working cylinder

He already said he tested for spark at that cylinder with success. Is the compression ok on that cylinder? If all the others work it can't be timing, and you've proven spark. Must be fuel or compression. I'm zero help when it comes to carbs.

Did you test the plug from that cylinder for spark? I've seen plenty of bad new plugs

Did you read his post? Not trying to sound krusty, but...

Yes, to all questions.




I did not personally do the compression test. My mechanic did and reported all cylinders were between 90 and 95. Not great compression, but enough.



Good point. Yes, sir. I can see the spark with the plug on the engine tin with the engine at idle.




It's all good. I'm not assuming anything at this point.

maybe the fuel isn't fully atomizing? Try switching the jet stacks and see if the problem follows...

I like Ian's thinking. Fuel has to be the highest suspect. Is the color of the plug different on this cylinder than the rest?

Are the carbs such that each cylinder is off a different choke/throttle body? Silly thought, but you could switch the carbs around to see if the problem migrates with the carb. I bought an excellent book about Weber’s that had a section on Zenith-strombergs that was what i was looking for at the time. I can dig it out.

Depending on the linkage, swapping the full carb from one side to the other could be a big deal. I'd def start with the jet stacks on the same side. It shouldn't take more than a couple minutes to switch 1 to 2. Hopefully the problem will follow and all that will be needed is a good jet cleaning.

intake valve not opening, bent pushrod or something?

Also check the idle jets and mixture screw port for obstruction

Goes back to my compression check question. He said his mechanic tested. Rusty, do you trust said mechanic's answers? We know it isn't timing, so it has to be fuel or compression. (Assuming the plug you tested for spark was actually the one pulled from that cylinder.)

Weber carbs run on the idle circuit about half way thru their range. A clogged idle jet or idle passage will cause this. It is much more common than you would think. Pull the idle jet and check it for infinitesimal debris and blow it out. If that does not cure it, pull the carb and clean the idle circuit with carb clean. Install a new inline fuel filter. Clean fuel is the key to Weber’s.

Charlie

Dirty plug? Pull the plug and wire wheel off the carbon?

Zach

I do appreciate all the replies. I'm taking notes.




That's an interesting idea. As part of the troubleshooting process, he tore down the carb and cleaned it. I can try swapping the jet stacks though.



More work, but it would certainly be a good test.



TDC on number one feels right. Valve adjustment went okay.



Roger.



Yeah, I do. But a second look at the compression on #1 might not be a bad thing. Yes, the plug I tested was the one pulled from that cylinder. Got the same result with the replacement plug.



Thank you. I'll double check his work if all else fails.




One of the first things I did when I pulled the car out was clean the plugs. I've since replaced them with another set.


I'll pick up the car tomorrow.

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.

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?

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.

Vacuum leak on the intake top or base? I would try switching the carbs.

Use propane....safe and effective...

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.

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

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.



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



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.



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.



Thanks for the encouragement, man.



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.

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.