My 91 F150 starts fine when it is cold, but when it is hot it barely starts at all. sounds like a bad starter when you turn the key. You get one burst of juice, then nothing. But the burst of juice starts the motor...so far. Ive had the electrical system checked out thoroughly...no problems. Mechanics are puzzled. What's the problem folks?













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It is probably the GM problem. Since Ford went to the GM type starters, with the solenoid on top, they inherited the hot start problem. The exhaust makes the solenoid really hot, and it doesn't like it much a r is really all it takes, that one is intended for GM, but I'll bet it could be made to work. Another avenue to approach would be; to make sure it had all the juice it wants, run an extra ground wire to one of the starter bolts.

 

Unless somebody converted this over to a 1992 or newer starter(which can be done) the 1991 starter doesn't have a solenoid on top.

1991 was the last year of the old style starters. The 1992 and newer starters do have one advantage, the full power to operate the starter doesn't have to travel through the fender mounted solenoid thus causing the contacts in the fender mounted solenoid to stick and the starter sometimes keep cranking after the key is released.

 

My trucks doing the same exact thing. (88 f150). I got headers though which set right on the starter. Literally. I'm trying to find a mini starter for mine at the moment. Sounds like you got a heat soak problem. Heat shield and header tape might fix ya out.