1978 F-150 odd starter issue

Asked by Dec 04, 2017 at 11:50 AM about the 1978 Ford F-150

Question type: Maintenance & Repair

I am rehabilitating a 1978 F-150 (300ci straight 6, 4WD) and I am having the oddest starting problem. The engine will start and run only as long as it is being cranked. When the key goes back to the run position, no ignition and engine shuts down.

Things I have done:
1) Replaced starter (it was seized up)
2) Replaced solenoid (just because)
3) Replaced the big fuse that is screwed to the body next to the solenoid
4) Yanked out the ignition switch and checked its function
5) Traced wiring continuity to and from the starter switch

I'm sure that the problem has a simple solution, but I am at wits end trying to figure out what is going on. It seems like there is no juice coming out of the "I" terminal on the solenoid. If I short the S and I terminals when someone is cranking it, it starts up and stays running, but the starter keeps going so I obviously can't leave it like that except for test purposes.

2 Answers

104,405

I think your ignition switch is faulty.

I ran a continuity tester over the contacts in all positions and they match what they are supposed to according to the guide I found. Next on my list is to manually connect terminals in the ignition switch socket with jumpers and see if that makes any difference.

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