Not Firing Properly

I have a quick question: I have a 1963 CJ w/ an F134. The number 4 spark plug is not firing. I checked the compression: 122 psi, the timing is dead on, switched plugs around (problem stayed w/ #4 cylinder), tried new plug wire (no improvement), pulled #4 wire from distributor cap (when held about 1/2 inch from tower, sparks great and idle smoothes out nicely). This happened this fall and I bought new plugs, cap, condensor, and rotor and all 4 were firing as they should. What could happen that would cause these symptoms in such a short time (less than 100 miles)? Thanks for your help!

 

I'd go for the plug wire again. Check it over real close, I've seen 'em break inside where you can't see it. Had a coil wire once that only had a small crack visible outside, but the inside had arced so much there was 1/2" of the core burned away until the spark couldn't jump the gap anymore. Carbon core plug wires are easy to crack.

 

Thanks for the replies. The #4 plug is wet with what I think to be fuel. It is black (running rich, needs carb work too). That leads to another question. Would a poorly adjusted carb cause just one cylinder to misfire? Doesn't seem like it would with the way the intake/head is designed. My problem is most likely ignition not carb related anyway. I'll switch the "bad" plug w/ one of the other three and see if the "bad" plug fires. Earlier, I switched the "bad" plug with one I had lying around.
I'm considering a Pertronix unit for the distributer. I have one on another car and I like it. Any thoughts on the dizzy being the culprit?

 

Ahem, plug wires? You said you got a good arc at the tower from that wire, did you hold it near the plug and get a good arc at the plug end too?

Cracked distributor cap? Damaged contact inside cap? Try new plugs? New plugs are cheap. Plugs gapped correctly? Check out all the cheap things first before you start throwing lots of money at it.

 

OK- Just went out in the rain and swapped some plugs around. The problem followed the "bad" plug. So I'm assuming a fouled plug on #4. What can cause this?

Not real sure what you mean by "is #4 pumping oil?" Haven't noticed any huge amounts of smoke out the tailpipe after the engine warms up a bit. Maybe the plug is getting fouled during the warmup period?

Something strange happened yesterday. I think the engine was hydro-locked. Never before has this happened to me so I'm not real sure that this is what happened, but the engine would not turn over. Sounded like a cylinder was bumping into a hard rubber block. Then I noticed a pool of fuel on the driveway after the engine started. I can't imagine where the fuel came from. No loose hoses or anything. Also, I noticed that there is fuel in the oil.This has never happened before and has not happened since (several starts since yesterday). As I mentioned before, the carb needs some work. New carb has already been ordered.

Could these two incidents be related?

BTW, the engine was reassembled this summer after previous owner had disassembled. New bearings throughout, rings, cylinders honed. The valves had already been assembled in the head and block when I got the engine. Possibly a valve guide problem? The #4 cylinder is at 125+ psi when warm if this has any bearing on the valve issue.

I'm sure you can tell I'm not a mechanic by trade. But I do appreciate all your input!

 

An oil fouled plug looks different from a fuel fouled plug. If you have too much fuel, it will be wet and sooty, but oil looks ... oily.
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

<edit> Yeah, "pumping oil" means oil getting past the rings or around the valve stems. You'd see blue smoke till the plugs fouled, then it wouldn't run - or at least the bad cylinder wouldn't run.

 

BTW if the plug is fouled and you didn't clean or replace it, it will likely continue to be fouled. If it's wet with gasoline, it won't work properly until it's dry, if not clean. Hardly anybody cleans plugs these days - I'd recommend new ones.

 

If you been playing with it for awhile and that cylinder hasn't been firing thats a good way to end up wit a bunch of fuel in the oil... called cylinder wash ( also comes from running way to rich) and will wipe out the rings and bearings if not attended to...

 

Thanks for all the responses. I will definitely invest in new plugs and wires when the new carb comes in.

About the fuel pump causing gas in the oil...would this happen if the float in the carb wasn't functioning properly? Could this be why the engine runs rich even after adjusting the mixture screw most all the way in? And why fuel drips from under the fuel bowl on the carb?

I appreciate you guys taking the time to read and answer these questions. I'm trying to learn all I can about what makes this engine tick. Thanks again!