Engine will not crank when hot?

1989 PONTIAC TRANS AM
34,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC
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SIXTY6GTO
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The car listed above is a GTA model. The car will crank over and start when it is the first start of the day or after letting car cool off for 3-4 hours after running the car to operating temperature. When the car is hot and trying to crank, I cannot even hear a solenoid clicking on the starter or anything. I do hear noise possibly from a relay under the dash. I do not suspect the VATS to be the problem since the security light does not stay on and I have checked my resistance on my keys, tried another key, and my problem only occurs when the engine is hot. I would like the diagram of the starting circuit for the car since there might be a starter enable relay under the dash and a wire from the neutral safety switch under the car that gets hot. I do not want to jump to conclusions and think it is the starter. I want to methodically diagnose this using the starting circuit diagram please. Thanks.
Jul 10, 2023 at 12:03 AM
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STRAILER
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Sure, here is a guide to help you with the testing and the starter wiring diagrams so you can see how the system works:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

and this guide can help as well:

https://www.2carpros.com/articles/starter-not-working-repair

Check out the images (below). Please let us know what happens.
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Jul 10, 2023 at 12:36 PM
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SIXTY6GTO
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Has there been a history of the PPL 6 wire going to the starter failing when it's hot? How can a wire provide power when cold but not when hot? I believe this may be the problem since I have seen a few people on YouTube possibly with the same issue.
Aug 8, 2023 at 8:47 AM
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STRAILER
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Does the trigger wire have power when in the crank position when hot? If so, then the starter motor is bad.
Aug 10, 2023 at 9:32 AM
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SIXTY6GTO
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I have not forgotten to reply to you Ken. I have been busy and need to get a buddy to help me while the car is on a lift because this car is so low to the ground and I need a couple extra hands to make the job easier. I will let you know soon. I am juggling other tasks in the driveway now. I appreciate your help so far. I will definitely get back to you soon.
Jan 19, 2024 at 10:02 PM
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STRAILER
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Sounds good, let me know :)
Jan 21, 2024 at 9:38 AM
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SIXTY6GTO
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I started up the car cold then drove it to the shop. I took the car to a shop with a lift and checked for voltage at the purple trigger wire connected to the starter at terminal "S". When the key is held to crank the hot engine, it will not crank but the solenoid can be heard clicking and there is roughly 9.5 to 10 volts at the trigger wire terminal while it is connected to the starter. Even after overnight cooldown the starter will click but not rotate to crank the engine. I believe the starter is bad. I am going to change the starter. on the 1989 Trans Am with a 5.7L . I hope I can get the starter out between the exhaust. Do you have the factory service manual steps to remove and replace the starter?
Feb 24, 2024 at 12:46 PM
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SIXTY6GTO
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I had power at the trigger wire when actuated. Therefore, I changed the starter, and this resolved the problem. It is important to mention that I had to loosen the Y pipe on the left and right exhaust manifolds to allow more clearance to remove and replace the starter. It was impossible to remove the starter without dropping the exhaust from the engine to gain another 1-2 inches wiggle room to have enough space. Once the exhaust was loosened, I was able to remove and replace it. My car is equipped with the N10 RPO coded exhaust as an option for this 89 Trans am GTA. This is also important to mention as others may encounter a different exhaust setup. The purple wire was in good shape and was secured back to the "S" terminal on the starter. Thanks for your help.
Feb 25, 2024 at 10:00 PM
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Thanks for letting us know, we are here to help, please use 2CarPros anytime.
Feb 26, 2024 at 11:24 AM