Another Setback

Today I was confident enough to take the truck to work.  That was a mistake.  I drove it around town yesterday (Sunday) without incident and I thought I had resolved the stalling problem.  Nope.  My office is about 15 minutes away.  About 3/4 of the way there it started missing.  I made there alright, but on the way home that evening the missing got worse and it finally stalled again.  I had to tow it back.

I thought that my problem was with fuel.  I noticed that air rushed into the tank whenever I opened the gas cap after it had been running.  A previous owner had replaced the gas tank recently and I assume that it was not properly vented.  Also, a section of the steel fuel line from the tank to the engine had been bypassed with hose.  I figured that because the tank was not venting, after running for a while pressure would build up and the pump could not pull any more gas.  Seems like a plausible explanation   To test my theory, I started driving it with the gas cap off over the weekend.  That worked for a while and I'm still convinced that it was at least part of the problem.

Now I am considering an electrical cause.  When it stalls, it turns over, but never fires.  Fuel is reaching the carb, because I can see the accelerator pumper squirting gas into the carb.  After it sits for a while (hours) it will start again.  There are some sketchy wire spices between the distributor and the coil (not the high voltage wire).  After doing some research, I think I am going to try to solder those together and put heatshrink over them.

I have also noticed a lot of carbon under the distributor cap.  I have heard of carbon tracking, but this is more of an all-over build up.  I will probably replace the cap and rotor, but I would like to know what is causing this.

Carbon under cap.  The dark spot on the left is where I wiped it with my finger.

Carbon on rotor and in distributor.