slow starter after cars warm

[kpc01]

Looking for help identifying a problem with a 90 coupe I'm working on. Starter works fine when its cold but when its warmed up its slow to turn over and sometimes won't at all.

things I know:
10 degrees timing
shorty headers so not much heat at starter
battery in trunk


-I tested voltage at the battery and get 12.4-12.5 (its been sitting a few weeks so I think the battery is a little low)
-voltage at the solenoid up front is same as above
-voltage going to starter from solenoid is around 8v when cold
-voltage going to starter from solenoid is around ~5v when warm

I just want to identify the problem rather then changing parts. I looked at ht starter and its a ultima (Orielly I think?) but was on the car when we got it.

thanks for any advice

[Venom]

If all of the starting system seems ok, I would look at the TFI module.

[lowthreeohz]

I've seen starters get heat soaked and do that

[JC316]

It's either the wiring going to it, or the starter itself. My money is on the starter.

[kpc01]

I'm thinking the start too but just wanted to see if anyone had any extra insight.

Next question. I've heard the 93 starters are better (smaller and more torque). Is this true? I looked them both up and the 90 starter is 10 teeth and 93 is 9 teeth but didn't know if I would be better off replacing it with a 93 starter? I'll double check my wires but seems like its getting enough juice, just pulling more when hot

[Venom]

go with a mini starter. They are much easier to install and have higher torque. LMR sells an SVE one that's awesome.

[shumpertdavid]

The voltage testing is somewhat pointless without seeing the amount of amps being pulled as well. If the ground or power supply is inadequate then the starting will suffer. As stated more than likely it is the starter, but you haven't done enough testing to completely condemn it.

[Slow Five-O]

I've seen starters get heat soaked and do that

This

I'm thinking the start too but just wanted to see if anyone had any extra insight.

Next question. I've heard the 93 starters are better (smaller and more torque). Is this true?

Yes. They're great and should fix the problem.

[talisman]

It's likely the starter. And if you want to convert it to a mini starter you also need to be prepared to do some wiring. They are also more expensive. Unless you need it because "race car" I'd just leave the stock one in there; stock units aren't THAT much more difficult to install, and the wiring is a PITA.

[0393gt]

You could try some heat shielding on the starter. Think I may do this myself.

[onjacks]

i had the same problem and it was a bad battery.

[Strychnine]

Bad grounding is always my first check. Corroded connections, excessive resistance, etc.

[AdRock]

The starter on my 95 F150 5.0 would turn a little slower when everything was warm. I ran a wire from the negative terminal to one of the alternator bolts, replaced the wire from the neg to the body. The alt was not able to charge the battery as well because of a mediocre ground. Once I did those 2 small wires the starter spins the same no matter how warm or cold.