Starting Problems when car is hot!

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GetX'd said:

Yeah - it's me again! The GTX turns over fine when totally cold. I tested the battery. Had to replace the "new alternator". Car turned over fine and started this morning. Took it for a 15 mile spin (first one in 35 years). Came back turned it off and it now it won't start again. It barely turns. I don't know what to make of it. New battery, new starter, new alternator, new voltage regulator. It seems when the car is hot it has the problem. When cold it will start.

Any ideas on what it could be? I'm wondering if the voltage regulator needs adjustment? Thanks for any and all help!

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I had an old pickup that did the same thing when it got hot. Check your ground wire coming off the battery. If it gets unusually hot, you will need a thicker gage ground wire.

Good tip Mike - I'm going to check all this stuff in the morning. I feel like heat has something to do with all this. Hope I can verify what it is. Will report back. Thought I had it licked this morning and was really disappointed in the set back.

I really appreciate all the input - it's been a long time for me with this car and I've forgotten what I once knew.

My guess, the starter gets to hot.
Wrap the headers near the starter.

kjalltrac said:

My guess, the starter gets to hot.
Wrap the headers near the starter.

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I'll take whatever I can get. That's occurred to me as well. I should wrap the headers and the Starter. Space is minimal there - A

Here's a starter wrap.

I thought I had a new voltage regulator on it. Found out the one on there is about 35 years old. Don't know if that has anything to do with problem but going to put a new Borg Warner on the car tomorrow.

Retarded the timing 5* from 16* before TDC to 11*. It didn't make a difference in the starting issue. Still starts cold - heats up after running then barely turns over. Why would the starter turn over so well when cold then not when hot?

I'm really pulling my hair out on this one. Tried most of the stuff posed already - except the starter wrap.

OK, just don't fall into the trap of throwing parts at it. There is a long way to go.

Understandable frustration from electrical problems… You need to start a process of elimination.
Battery good? does it have the proper cold cranking rating.
Is starter good , test Using a jumper to bypass the solenoid is a trick that will show if the starter motor spins or not. If the starter works when bypassing the solenoid, the problem is in the solenoid or ignition circuit.

Another test that can be performed on a starter is a no-load free running test with the starter removed from the vehicle. With the starter firmly supported in a large bench vice (do NOT clamp too tightly otherwise you may crush or damage the housing!), use a battery and jumper cables to power the starter. Hook the negative cable to the starter housing, and the positive cable to the battery positive lead on the starter. Most starter motors should spin about 2500 to 3000 rpm. If the starter turns very slowly or not at all, you need a new starter.

A possibility that engine heat may be increasing the resistance in the starter windings. or cables...
then start checking the battery cables for excessive resistance.

Voltage Drop Testing
from my trouble shooting manual..
Does your engine crank slowly or not at all, but when you test the battery and starter both are fine? What about an alternator that puts out its normal charging amperage but can't keep your battery fully charged?

An often overlooked cause of these kinds of problems is excessive resistance in the high amperage circuit. Loose, corroded or damaged battery cables or ground straps can choke off the normal flow of current in these circuits. And if the current can't get through, the starter won't have the muscle to crank the engine and the battery won't receive the amperage it needs to maintain a full charge.

Nasty looking battery terminals that are blooming with corrosion obviously need cleaning. But many times corrosion forms an almost invisible paper-thin barrier between the battery terminals and cables. To the naked eye, the terminals and cables look fine. But high resistance in the connections is preventing the high amp current from getting through.

The same goes for battery cables with ends that have been beaten or pried out of shape, or have had the ends replaced. If the clamp isn't making good contact with the battery terminal all the way around as well as its own cable, the cable may have too much resistance and restrict the flow of current. The same goes for ground straps that have loose or corroded end terminals, or make poor contact with the engine or body.

Cranking problems can also be caused by undersized replacement battery cables. A wire's ability to pass current depends on the gauge size of the wire. The fatter the wire, the more current it can safely handle. Some cheap replacement battery cables use smaller gauge wire, which may be camouflaged with thicker insulation to make it appear to be the same size as the original cable. But the cable doesn't have the capacity to handle the current.

It doesn't take much of an increase in resistance to cause trouble. Let's say a 120 amp alternator operates in a circuitthat has a normal resistance of 0.11 ohms. If that resistance were increased to 0.17 ohms because of a bad wiring connection, the alternator's maximum output would be limited to 80 amps. In other words, an increase of only 0.06 ohms (almost nothing!) would reduce the alternator's maximum output by almost a third! Under light load, the drop in charging output might not even be noticeable. But in a high load situation, the alternator wouldn't be able to keep up.

CHECKING CONNECTIONS

If you use an ohmmeter to measure across a heavily corroded battery cable or ground strap connection, or one with only a few strands of wire that make contact with the end clamp or terminal, the connection may read good because all you're measuring is continuity -- not the ability to handle a high amp current load. The connection may pass a small current, but when a heavy load is applied there may not be enough contact to pass the extra current.

So how do you find these kinds of problems? You do a voltage drop test.

VOLTAGE DROP TEST

A voltage drop test is the only effective way to find excessive resistance in high amperage circuits. It's a quick and easytest that doesn't require any disassembly and will quickly show you whether or not you've got a good connection or a bad one.

To do a voltage drop test, you create a load in the circuit that's being tested. Then you use a digital volt meter (DVM) to measure the voltage drop across the live connection while it is under the load. Voltage always follows the path of least resistance, so if the circuit or connection being tested has too much resistance some of the voltage will flow through the DVM and create a voltage reading.

Pops1967GTX said:

Understandable frustration from electrical problems… You need to start a process of elimination.
Battery good? does it have the proper cold cranking rating.
Is starter good , test Using a jumper to bypass the solenoid is a trick that will show if the starter motor spins or not. If the starter works when bypassing the solenoid, the problem is in the solenoid or ignition circuit.

Another test that can be performed on a starter is a no-load free running test with the starter removed from the vehicle. With the starter firmly supported in a large bench vice (do NOT clamp too tightly otherwise you may crush or damage the housing!), use a battery and jumper cables to power the starter. Hook the negative cable to the starter housing, and the positive cable to the battery positive lead on the starter. Most starter motors should spin about 2500 to 3000 rpm. If the starter turns very slowly or not at all, you need a new starter.

A possibility that engine heat may be increasing the resistance in the starter windings. or cables...
then start checking the battery cables for excessive resistance.

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Thx Pops - I really appreciate your knowledge and input. I will try the above and report back on what happens. I really appreciate all the feedback from everyone!

Since your car has sat for an extended period of time also pay close attention to your battery cables as well as any and all ground straps. Electrolysis can form and be hidden inside the plastic/rubber coating on the cables. This will definitely cause the problems you are having. Even though the cables appear good they can hide this issue. We have run into this many times. Disconnecting the battery during extended times of having the car parked is the only way to prevent this. Also slow charging a battery while having both cables connected may aggravate this situation. Its always best to remove the ground cable when charging the battery in the car.

Okay guys - here's an update. I put in a new voltage regulator, new battery cables, new (previously didn't have) separate ground strap. Charged the battery and tested the starter. I only put 5 miles on it to heat it up - but the car started while heated up and again after it cooled down a little.

I'm praying the solution was a combination. Of the above. I should be able to tell in the next couple of days of testing the car. Wish me luck and thank you to all of you guys that gave me advice. This has been trying for this old novice.

I'll report back the success - or come crawling back ...

Great news!

Another cause on new rebuilt starters is bushing that are to tight so drag when hot
warn main bearings tighten the gear clearance and cause drag
but most likely bad connections both hot and ground

Pops1967GTX said:

...
Question what is setting on timing….ignition advanced too far ?

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THis is what I wonder too. Where is your initial ignition timing set? If I set mine above 22-24 initial, it will do the same thing. It would start fine when cold, but turn over very slowly when hot.

I wonder if it could be tested by taking the lead off the coil for cranking when hot ??? At first, I put a switch to interrupt power to the ignition so it will spin and then once spinning turn the ignition on.

OOPS missed the second page of responses. See it has moved on.

I know you said it was new....

I had the identical issue on my Charger and a new starter fixed it.

It would run fine. Shut it off and try to restart and you would swear the battery was near dead or the engine was heat seizing. Let it sit for 10-15 minutes and it would start like a new car.....

Well guys I'm not crawling back.... I just signed in to let you know that I believe the problem is fixed. It's hard to tell but I believe the culprits were both the voltage regulator and the battery cables. Plus the new ground strap.

Thx to a numbEr of members I made those changes and have tested the car several times - several ways. It seems to start fine now cold or hot.

Thx FBBO brothers - you guys really helped me out!!