Bill Ball

A bad crank sensor prevented the starter from cranking?

Landseer

Intermittent contact yellow wire in 14 pin might prevent.
Bad front harness leading from 14 pin.
Problem with wiring at jump post, heat triggered.


Need more data at this point.
Hopefully data shows multiple issues but excludes tbf.

Podguy

Bill,

I am with you as a starting point. It sure sounds like the engine is dragging. The first thing I would do is to run the engine until it is hot. Then when it won't start put a wrench on the damper bolt and try to turn the engine over. If won't turn then you have located the problem as deep and sad as it would be.

It is true starters can degrade with heat. I bought a few ford starters from a discount place. Took them back for exchange several times. Finally I went to a quality parts house and bought a good starter and the problem went away. The starters right out of the box would not start the car when it was hot. I think I went through three or four before the store objected and gave me my money back. And this was from a major chain.

928s4forme

Brilliant! I will unhook the yellow wire at both ends and ground one side when both cold and hot to see if there is any change in resistance through the harness. That would make perfect sense as to why the starter isn't getting enough current to turn her over...will keep you posted. Thank you guys for helping me on this!

WallyP

When the starter does not operate, does it make any noise? The starter solenoid must operate before the starter motor will run. Operation of the solenoid makes a "clack" that should be audible in a reasonably quiet place. No clack, no start.

If there is a clack, but no starter, the problem is in the solenoid or the starter motor, or the engine is locked. If there is no clack, the solenoid is bad, or, more likely, isn't getting power.

Get a piece of stranded, insulated wire of 14 or 16 gage. Strip about 1/2" on both ends. Separate the 14-pin connector, being very careful to avoid letting the pins slip out. Stick the stripped strands on one end into the female side of the yellow wire in the corner of the connector and reassemble the connector.

When you touch the other bare end to the jump start terminal, the starter will operate. WARNING - DANGER The starter will operate even if the car is in gear. Be CERTAIN that the transmission is in neutral.

If the starter now functions, the problem is likely to be in the yellow wire somewhere between the short jumper wire and the ignition switch or the ignition switch. If the starter does not operate, the problem is likely to be in the yellow wire to the solenoid, the solenoid, the starter, or the motor is locked.

Rod Underwood

No it would crank but not start until it cooled a bit

928s4forme

Hey Wally,

The starter solenoid engages (clack) and I hear the starter try to turn but either locks up (motor) or is weak (current). All the lights dim (panel, interior, etc.) and the starter does try to crank. The starter is new and tested before I took it home to put it on. Also, I had another spare good starter from my 88 parts car that tested good as well and thought it was bad, hence the reason I bought the new (Bosch rebuilt) starter. I believe both you and Landseer may be correct. I am hoping it is the front harness and/or pin connector, and not a tight engine lower due to a TBF. (A little prayer at this time is in order). My multimeter at both the charging post and the battery will not zero out on volts when cranked hot which leads me to believe that I'm getting nowhere near the 65+ amps both the new starter and my good spare are capable of pumping out. At best, I am getting a third of that, based on Ohm's Law. That's why I feel you guys may be right. Hoping to confirm this soon... keep you fingers crossed everyone.

928s4forme

Okay Guys,

I went home at lunch time to test a theory...

I started her up and she ran perfectly until the very second the electric fans kicked in...the very second the fans came on, the rough idle (idle hunt low to high back back down again over and over). The car sputtered to complete engine stop. tried to start it and got the usual not enough power to crank over deal. All the lights dim when I try to crank, but only get a half a turn out of the flywheel and no power. So it has to be electrical in nature. Literally , the very second the fans came on the demon appeared. Before that, perfect.

What are your thoughts? Where would you start to look?

WallyP

If the solenoid clacks, the problem is not in the yellow wire.

The problem might be:
- Starter is not getting sufficient amps to turn the engine. This can be due to a bad connection at the battery, the rear ground strap, the ground strap or its connections under the engine, or at the starter; or a faulty battery. None of these sound likely in your case, since a worn starter is the only thing that is likely to be temperature related.
- High drag in the engine. Could be thrust bearing failure or poor quality oil.

I think that the next thing to do is to check for excessive pressure on the flex plate, and measure the crank clearance.

OK, your post came in while I was writing this. Sounds like a bad battery...

Lizard928

Replace the battery to chassis ground,
Replace the engine to chassis ground.
(you can use engine jumper cables to do this for testing)

Bill Ball

This is a bad sign...keeping fingers crossed. Do some of the other electrical tests, but crank endplay is a basic, important, periodic test and not hard...

https://rennlist.com/forums/928-foru...pictorial.html

Podguy

Did you put a wrench on the front pulley and try to turn the engine by hand. Do this first and eliminate the possibility of a heart break. If it will not turn by hand then.... well you have a real problem.

jetrainor

The TBF on my 87 was......start and run fine but no restart when warm....wouldnt turn over...i noticed after i swapped a 88 engine in and had the old one on an engine stand that the orange harmonic balancer on the TBF motor was pushed out so much that the plastic cover on the front was cracked...25,000 kms later the drive shaft has migrated zero thanks to Constantines clamp.

928s4forme

Everyone,

I believe I have found the problem, but I need a little help in order to proceed. I started the car today after resoldering pin 1 on the male end of the 14 pin connector near the charging post and she ran great. I connected my multimeter to the charging post and ground to body and got 13.74 volts at idle consistently. I throttled it a few times to speed up the warming process and she ran great. After about 25 minutes I throttled her again (no pun intended here). She died. I pulled the connector and then checked the female side of the connector for voltage. At pin 10, I got voltage...but only 11 volts. Charging post had 12.5+ and battery did too. This must be the issue. There just isn't enough current to turn the starter. (Thank God!!!) Can anyone tell me what the front engine harness is pinout is for an 87-88 s4? I want to trace it back and slay this gremlin!

I'm almost there guys...

Mongo

While it was in the garage and hot, you should have tried to hand turn your engine with a 1/2 drive ratchet and a 27mm socket on crank pulley. That alone would relieve some people here about thrust bearing failure.