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no spark on one cylinder, intermittent

7K views 5 replies 4 participants last post by  chevy1500z71 
#1 ·
a few days ago i noticed that when i fired my truck up it was clearly down a cylinder or 2, i drove it down the street a bit and as i drove it some i could feel my dead cylinders popin back to life hear and there and eventually id be back in business and it would run like a raped ape like always for as long as i want too. till a few days later, same deal, goes aways after a short drive and im back in business like nothing ever happened. this went on for about a week untill today when it did the same deal but it wont clear up. i cant get it to run good. i went through all the plug wire and theres no problems, i put a timing light on all the plug wires individually to check if they all get power from the distributor cap. it seemed like cylinder #7 was not getting any spark so i took the wire off and inspected it and it was fine the cap looked fine, no cracks or anything, i put a different spare wire on it anyway and no difference. so i took the wire off all together and fired the truck up and sure enoguh it ran just like it had been running so that cylinder has to be getting no spark right? but i held the magnetic pickup from the timing light near the terminal and i could see it arcing, so that terminal was putting out juice, no? i dont know what to think, my distributor is old, but wouldnt all of my cylinders be down if the dist was going bad? the cap and rotor are pretty new. what do you guys think?
 
#2 ·
Electricity is both smart and lazy. Just because it`s getting fire at the cap doesn`t mean it`s getting it to the plug. If there is another path of less resistance than to the plug, the spark will take that path. This is why many rodders use spiral core spark plug wires for there lower ohm rating. Pull the number 7 plug and replace it, as it sounds as if it`s just simply fouled out.
 
#4 ·
sounds like plug . if it's is , it will do what you said with not as strong a spark .
old timers , some on here , used to leave the boot loose at plug so you have a spark , jumping to plug to keep from fouling .this cleans the plug enough to get by .
old tractors setting up ,my granddad did this regular on his .
 
#5 ·
so you guys think its just the plugs then? well thats just too easy. ill give it a try.

i have taylor spiral core wires on there now, they have been burned on the headers before but i have trimmed them all up and put heat sleaving on them, they are all in good shape.

this is probably the longest iv been on a set of spark plugs, normally im really anal about having a good set of plugs, if something happened with my tuning and i ran it really rich or something, i dont know, but its always something, normally 3,000 miles is about the longest i go. these are about 6,000 miles old. by most standards these things are new, but i guess my motor is just very hard on plugs being that its supercharged and runs very rich under boost.

ill clean up all my plug wires and inspect them and change the plugs and see what it does, thanks for the help guys.
 
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