I spent the weekend screwing with my '86 F150 302 EFI. It died Friday night and I replaced the TFI and ign coil (both were dead) and it ran fine afterward. Yesterday I did plugs, cap and rotor and afterward the damned thing would run for a short period of time and die but would restart if the key was cycled. I went over everything I've done to no avail. Long story short this morning I finally pulled the dist and TFI again and put some heat transfer paste I used on my laptop motherboard and it ran fine with no issues afterward.

Bottom line the dielectric grease (even the stuff supplied with the new TFIs) doesn't appear to transfer heat like it should. This is the 3rd replacement (not counting the original) and I believe that's what roasted them all. I'm not too confident about the one that's in there now but it's a Motorcraft so I'm hoping it'll have survived the experience. I bought a spare just in case tho as it's a 15 minute replacement even by the road.

I didn't see this on any other threads, hope it helps someone else save time.

Dana N.

 

If the ICM overheated, it would never work again. The paste doesn't transfer heat - it just IMPROVES the transfer of heat, compared to being dry. So it wasn't adding the paste that made it run - it was you disturbing things (like wiring) &/or allowing other things to cool off (like a fuel pump) that allowed it to run again. You didn't actually diagnose anything; you just got lucky. The problem WILL reappear, and eventually, the time & disturbance of changing the ICM won't let it run.

The best diagnosis for an ignition problem is in Haynes Ch.5 (usually Sec.5 or 7, depending which edition you get):


(phone app link)

But this might not be an ignition problem, so that procedure may result in no fault found.

 

Well, the fuel pumps ran for a second or so after the engine died which eliminates a pump problem. Also it died like shutting off the ignition, not like it was running out of fuel.

I checked and rechecked all the work I'd done including connectors (looking at the terminals) and wires to see if something was grounded. I was even suspicious of the new rotor and cap but nothing I did made a difference until I installed my test harness and ran checks on the 12v, ground, PIP and coil signal from a page I found off the Internet. When the engine died I had 12v, ground, PIP but no coil which tells me the TFI was dead. When I cleaned the dielectric spooge off and put the white stuff on it worked, including idling for 1/2 hour or so and through several hot soak starts and probably an hour of drive time. Had there even been a poor connection between the TFI and the distributor I wouldn't have had a PIP signal. All the other connections were tight and clean.

While my initial thoughts agree with you the results speak otherwise. At this point I can't see any other reason for what happened but I guess run time will tell. I'll add to this thread if there's anything new.

 

No, it doesn't. And there's a lot more to go wrong with the fuel pump system than just the pump(s).Not the gold standard. Rely on Haynes &/or Ford (which is where most of my captions come from).I'm not sure what you mean by "no coil", but if the ICM was dead, simply spooging something different onto it wouldn't revive it.

 

No, it doesn't. And there's a lot more to go wrong with the fuel pump system than just the pump(s)

The pumps would run after the engine died. The engine died as if it were running out of spark not fuel. I've had plenty of experience with both symptoms. It was 100% an ignition problem.

Not the gold standard. Rely on Haynes &/or Ford (which is where most of my captions come from).

True there's a lot of junk to be found but this page was pretty straightforward and it coincided with my Ford EVTM and chassis manual but was easier for me to see what the tests did and how it was supposed to work. I had 12vdc in, ground through the processor and a PIP signal even when it wouldn't start. When it ran I could see the TFI trigger the ignition coil but no trigger when it wouldn't start. I've driven it since Sunday and it's started and run every time which it would not do before. Also it's not unheard of: just not for Ford so much. GM had intermitten issues with HEI ign modules (and even more problems with the pickup coils). Back in the late '80's I worked for an Olds dealer and had a car with similar symptoms get towed in. It had a new ign module but the tech that had installed it elsewhere neglected to put any of whatever GM recommended back then on it. The module tested good with the GM tester so my tech tried putting the paste (or whatever it was) on and it ran fine with no problems too.

As a sidebar; in the late '70s I worked for a Chevrolet dealer and our service rep was cheap. If we had a warranty vehicle with an intermittent ign module that tested good out of the vehicle we had to reuse it because if he tested it and it passed he'd charge the claim back to us. I know we had to let several go like that. Not the best way to go but it was how the circumstances dictated as it wasn't our money or rules.

 

As an update I've driven it around 1,000 miles, some of it towing in hot temps, since I figured out the issue and have had no further troubles. I'm still using the TFI that was dying and it hasn't shown any symptoms since I used the paste instead of the dielectric grease supplied with the new module.

Cheers!