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Strange issue with a 2001 Grand Prix (3.8L vin K)

No crank when the car sits in the hot sun for a few hours, has nothing to do with a engine hot soak. All dash light seem to pilot, just no crank.

If you let it cool off after the sun goes down a bit it will crank and start. All you have to do is park it in the hot sun (Texas 95 degrees F), even if the engine bay is cool after a few hours it will not crank.

Starter has been replaced.

As far as my research shows the ign switch is fed form the main panel (40a fuse) under the hood (near battery) directly to the ignition switch, then goes through the neutral safety switch to the starter, no theft deterrent intervention. I have tried moving the shifter up and down the range with key in start position with no luck, so I assume neutral switch is good.

Schematic pulled from AllData, appears to be the way GM has done it for ages, if anyone has better data on the wiring please post or link to it.

enter image description here

I cannot do any diagnosis until Tuesday, check voltage in and out of ign switch, same for neutral safety switch, check voltage at starter solenoid with key in start position. Check Starter install and wiring.

Has anyone seen this specific behavior on this model or similar before?

I will post back on Tuesday if I learn more.

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    Nothing at all when in the sun? I mean, no crank, and no solenoid clack ? – SteveRacer Aug 1 '16 at 3:45
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    I think your description is saying the underhood fuse block and starter are out of the equation. I'd be looking at the ignition switch as the culprit. I'd suspect the Neutral Safety Switch is also located directly on the transmission, so that would be left out, but it should also be easily bypassed to check it out. Like I said, most likely the ignition switch or wiring inside of vehicle is at fault looking at the diagram and your description. It may be there is a contact which is opening up when things get hot, not allowing electricity to flow. Just spitballing. – Pᴀᴜʟsᴛᴇʀ2 Aug 1 '16 at 13:07
  • @SteveRacer, no crank, no voltage to starter solenoid. – Moab Aug 2 '16 at 20:10
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After diagnosis it looks like the ignition switch, when it does the no crank I can hold the key in the start position and wobble the key-lock cylinder around and it will crank, its like it does not quite engage the switch when the interior temps get to a certain point, strange issue I have never run into before but think I found the problem or least narrowed it down to the switch or gears.

Qualified the neutral safety switch by bypassing it.

It is either the ignition switch or the gear mechanism from the back of the lock cylinder to the switch is worn out. Owner says the switch and lock cylinder was replaced 90 days ago but not sure of the quality of the switch. He wants a guarantee the switch will fix it but cannot do that due to the possibility the gears are worn just enough to cause it, would require quite a few hours to disassemble that mechanism to check but does not want to pay hours required, so I cannot guarantee the diagnosis without total disassembly.

Thanks for the comments.

  • On the Ford Focus(?) the ignition switch housing wears over time and requires a replacement of the housing. Maybe it's something similar e.g. The housing expands and requires more fiddling with the key. – Ben Aug 3 '16 at 23:54
  • That could be it, the owner wanted a guarantee without further diagnosis, so I passed on the repair. No pay, no fix. – Moab Aug 4 '16 at 1:42

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