97 F150 won't crank
Posted: Fri Jan 25, 2019 10:44 am
Bill's father in law has one in his backyard that he'd like to resurrect for plow duty. It won't crank. Yes, Ford circled the problem.
BBB Industries has provided this handy starting system wiring diagram.
The truck is an auto. But need to confirm if it has RAP or not. RAP is not Retained Accessory Power. It is anti-theft (my bad but I blame Ford - Remote Anti-theft Personality module is the dumbest and least logical name ever). If it has anti-theft, there is an anti-theft module that controls a starter disable relay. Stupidly (or maybe smartly if they counted on the system failing down the road) the way it works is the starter disable relay is normally closed which enables the starter circuit. If the anti-theft system wants to disable the starter, it actively grounds this relay, which then disables the starter circuit. That's dumb but means the failure mode is that the truck will start which is good depending on when in the truck's life you are dealing with starting issues...
But anyway this is pretty simple. Other than the starter disable/anti-theft relay which is normally closed (and can be jumpered out anyway if suspected), I'd do the following things:
- First I might start at the end, and if the starter solenoid control relay was accessible I would consider jumping that out and seeing if the starter engages. If so, then I'd start at the beginning to see why the ignition switch won't do anything.
- Check fuse 21. Can use test light to check the pin 29 side (downstream side) of the fuse when holding key in crank to see if it lights. If so, this means the ignition switch works and fuse is conducting power.
- With anti-theft, the relay defaults closed but could remove and jump pins 30 and 87A while ignition switch is in crank.
- If still no joy consider checking clutch pedal position switch jumper. It has a simple function but just remove if easy and use DVM to ensure it is shorted in pins 5-6, 1-2 and 3-4. Probably is fine.
- Next, need to examine the range selection switch. I think this is likely the issue. Either remove and jump pins or attempt adjustment. Or try starting in a gear other than P or N if maladjustment is suspected (be careful). If built before 6-24-96, jump pins 4 and 1 together. If it has the newer digital switch (whatever that means) jump pins 10 and 12 while cranking. I suspect this will work as there is nothing else to check if you already did step 1 and the starter engaged.
- Well technically the relay you bypassed in the first step could be the culprit IF the range selector switch passes all the tests.
Then see if she'll actually fire up and run. And move....etc.
BBB Industries has provided this handy starting system wiring diagram.
The truck is an auto. But need to confirm if it has RAP or not. RAP is not Retained Accessory Power. It is anti-theft (my bad but I blame Ford - Remote Anti-theft Personality module is the dumbest and least logical name ever). If it has anti-theft, there is an anti-theft module that controls a starter disable relay. Stupidly (or maybe smartly if they counted on the system failing down the road) the way it works is the starter disable relay is normally closed which enables the starter circuit. If the anti-theft system wants to disable the starter, it actively grounds this relay, which then disables the starter circuit. That's dumb but means the failure mode is that the truck will start which is good depending on when in the truck's life you are dealing with starting issues...
But anyway this is pretty simple. Other than the starter disable/anti-theft relay which is normally closed (and can be jumpered out anyway if suspected), I'd do the following things:
- First I might start at the end, and if the starter solenoid control relay was accessible I would consider jumping that out and seeing if the starter engages. If so, then I'd start at the beginning to see why the ignition switch won't do anything.
- Check fuse 21. Can use test light to check the pin 29 side (downstream side) of the fuse when holding key in crank to see if it lights. If so, this means the ignition switch works and fuse is conducting power.
- With anti-theft, the relay defaults closed but could remove and jump pins 30 and 87A while ignition switch is in crank.
- If still no joy consider checking clutch pedal position switch jumper. It has a simple function but just remove if easy and use DVM to ensure it is shorted in pins 5-6, 1-2 and 3-4. Probably is fine.
- Next, need to examine the range selection switch. I think this is likely the issue. Either remove and jump pins or attempt adjustment. Or try starting in a gear other than P or N if maladjustment is suspected (be careful). If built before 6-24-96, jump pins 4 and 1 together. If it has the newer digital switch (whatever that means) jump pins 10 and 12 while cranking. I suspect this will work as there is nothing else to check if you already did step 1 and the starter engaged.
- Well technically the relay you bypassed in the first step could be the culprit IF the range selector switch passes all the tests.
Then see if she'll actually fire up and run. And move....etc.