Hi
Thanks for the reply. I have a 77 F350 with a 351 and it has given me trouble free farm service for the last 3 years. Recently, it suddenly just started dying when it reaches temp and wont start back until it reaches ambient. I found this part had the wire loose and hoped that was my gremlin but i guess not. So, with that ruled out, I am back on the hunt for the cause of this. I have spark tester and the spark plugs and coil have 30k when its cold but i couldn't tell what it was hot b/c the sun was shining right on it. Any educated guesses or common causes of this?

THanks
Buddy

 

Sounds like it's either the coil or the Duraspark ignition box. Neither part are very expensive. Some of the cheap aftermarket boxes aren't of the same quality of an original Motorcraft box, so consider than when shopping.

 

Just FYI, while the engine will run just fine without that part connected, they "can" sometimes cause a problem with the engine NOT running when they fail internally.
What I mean is that, because the outer case of the capacitor/condenser/thingy is mounted to metal, if there is an internal short (or whatever happens when the voltage can get to the outer case) it can kill a perfectly running engine.
That's why I always recommend people disconnect it when testing for a no-spark situation. Even if it's not the problem, at least it is an easy way to eliminate one possible gremlin.
Same thing for the charging system. If something is not working, disconnect the radio noise suppressor temporarily to see if that's the problem.

Had it happen only once to me, but it left an indelible memory!
Same for the time the points "arm" (for lack of a better term) and isolator became conductive on my first motorcycle and stopped the ignition from working. It acted like the points were always closed, because they were in effect always grounded through the points plate.
Apparently 20 years of being exposed to oil vapors inside the engine were enough to cause an otherwise non-conductive material, to become conductive.

Sometimes you have to think out of the box to troubleshoot. And get very familiar with your ohm-meter!

Paul

 

Troubleshooting has always been and continues to be my weakness

 

Well, we should be able to help at least to a certain extent, even from way out here in internetland.
A few easy tests to start with, to narrow things down, perhaps.

 

I appreciate that, The electrical testing is my particular weakness. I don't know a general sequence of testing other than to just test everything in the particular system, which can be very time consuming. Maybe I can draw on the experience and wisdom shared here to become more proficient..