Another won't start when hot issue
 

I've done a lot of searches on here first, and all I got was more confused. I have a mini starter on by '76, and it won't turn the motor over when hot. First, I wrapped the starter to isolate it from heat. That didn't work. I took the battery to Autozone, and got it checked, and it's good. I even had them check my alternator. Yep, it's fine - putting out 140 amps. So I check the voltage on the battery itself - 12.8 volts. Check at the starter - 12.6 volts. So everything leading to the starter is all good whether the motor is hot or cold. But it won't crank over when HOT even with a blanket! It will click louder than hell when I turn the key, but no rotating the motor. I'm thinking of maybe getting a remote fender mounted solenoid kit or something from MAD Electrical to try and fix it but I dunno. I need some advise on this.

I had the same issue with my 79 T/A it was the starter solenoid. Replaced havent had an issue since.

First - Make sure it is out of gear. On a GM starter, If you can jump the fat battery voltage terminal to the tiny "S" terminal and it actually cranks, the relay will help.

Once you go to a mini starter, you should never need a relay.

I would look at the mini starter. Maybe try to jump it and see if it cranks. Use a hand held remote starter switch or maybe you can do it with a screwdriver on your setup. If you get no crank with direct battery power going to it, your starter is probably toast.

If it does crank, you need to find where the high electrical resistance is in your circuit or as a last resort, add a relay.

I agree with jumping it directly to get the solenoid/relay out of the circuit. Then it's just the battery and starter. If the battery is cranking it well when cold, then it is likely not the issue. Though I do wonder about the readings in the 12 volt range. To my knowledge, I would expect 14 volt range.

When I had this problem on a car (not a vette), it was the starter. The winding insulation degrades and some of the current starts passing between the winding loops, basically a sneak circuit which results allows some current to avoiding running through the entire length of the windings. This weakens the magnetic field. When the the starter is hot, this effect gets worse. If it's humid, it is further weakened when the insulation absorbs moisture.

12 + volts at the starter is fine. I have not seen a battery that has a 14 volt charge just sitting there with the engine not running. The higher voltage occurs once the alternator begins to charge. So..in my opinion..it is not your battery...especially if you did a 'load test' on it also to make sure you have enough cold cranking amps.

'Starter blankets' may keep heat out ...but they are also a blanket and can keep heat in also. Using a IR gun and seeing how hot it is might surprise you.. Actual heat shields that still allow air to flow around the starter can help if the starter is right near a header or exhaust pipe. I have fabricated up a heat shield for the exhaust and also one for the starter to aid in this if the owner does not want to ceramic coat the exhaust parts inside and out.

Either do what you are thinking by adding in a remote solenoid or get that one replaced. Just do not be surprised if you still possibly have some issues due to the armature area of the starter is still getting so hot that it does not want to work.

HEAT as you know is an electrical systems nemesis.

DUB

Do you [still] have a primary ground wire running from the right-side frame to the right engine motor mount bolt? That is the ground path for starter current (via the front starter support bracket). If that has been removed or has bad wire/connection, the engine will be hard to start (or impossible to start) when it is hot.

Lots of wasted money has been spent trying to chase down the elusive (and non-existent) starter heat soak issue. The starter really doesn't care how hot it is, as it mounts to the engine block and is adjacent to exhaust down pipe. But, if you have a poor ground wire to the starter, very little current will flow through the positive (+) cable, as well. And, the hotter it is, the higher the resistance in wiring, and the tougher it is to start.

About 25 years ago my "69 wouldn't start hot. I replaced the solenoid and it's been fine ever since.

Have you checked the grounds? If the ground is loose or corroded it would work fine when cold, but once it heats up it'll create resistance and not work.

Check the ground to the bellhousing and the condition it's in.
Also check the battery ground to the frame, it it's swollen it needs to be replaced.
Again, both could cause this exact issue.

Willcox :thumbs:

I do have a remote starter switch. Great idea, I'll try that tonight

I understand you. With the motor running I get 13.6+volts at the gauge and battery. I do have Hooker Super Comp headers, but they are 10 years old and were Jet Hot coated when they were made, and just last year I spray painted them with "ceramic coat" paint. But Jeez does it still get real hot under there

I was looking at this last night. I DO have a real thick battery cable type that goes from the frame to the motor mount (right side) But the ground wire (smaller one about 14 gauge) is bolted to just one of the starter bolts. Maybe I ought to just move it to the motor mount or frame grounding point?

Okay, went to the car tonight , checked all around . 12.5 volts all around , gauge, battery, and at the starter. Relocated starter ground wire to the thick cable on the frame. Hooked up the remote starter switch. It started right up. Then I ran it about 20 minutes or so revving it up a couple of times in between. Water gauge at 203 degrees when I shut it down . Waited 5 minutes and tried to start it up. No dice , same thing. I think the solenoid or the armature like DUB suggested are the culprits. Anyone second the motion?

I second. .After it's warmed up and shut down, first as someone said, if the car is a manual, put it in neutral, parking brake on. Then I'd bypass the solenoid and put 12 volts straight to the starter to see if it turns over. If yes, then it's the solenoid. If not, then it's the starter most likely due to the armature winding insulation degradation.

I guess the obvious question is how do we know its just not a defective starter?

next time it doesn't work take it out of the car and do a bench test of it....

Yeah, I thought AutoZone checks starters too, don't they? Or can I do this by just putting 12 volts to it on the bench, and jumping the solenoid?

My car is an auto. It has a 2004r stage 3 build from BowTie

If you bench test it make sure you strap it down before applying 12 volts to it...…...a good starter may jump several inches from the sudden torque.

Only does it hot, huh?

Where's your timing at?

I'm taking your hint. It may be too far advanced, right? I thought of this but it has never done this before at the present timing. I have a MSD mech distributor, no vac advance, and all I know is that I have it "all in" at 34 degrees by 2800 rpm. I never bothered to check the initial, which may be a good idea. I also changed to the black bushing in the dist to make it come on quick

For sure! I just might leave it loose , and just creep somebody out I don't like standing next to it!:rofl: