Hi guys, I just bought a vette a couple months ago, it's a 1987 manual tranny, the 4+3 kind. Anyways, the other day I was driving it and I stopped at the store, when I came back to start it, it wouldn't start. I know it's not the battery, and everything came on like it would normally, it just wouldn't turn over. So I called a tow truck, when he got there (about 30 minutes later) it started right up. So my mechanic looked at it and he said everything checked out fine, it started fine for him everytime. So now today I drive the car, runs fine, when I stop at a store, come back 15 minutes later, go to start it, I crank it for a short crank, it cranks, but when I release the key and go to turn it again, nothing. No clicking, no nothing. All the dash lights are on everything lights up like it should, but it won't crank. So, I call my mechanic again, he comes out to check it(about 15 minutes later), and guess what....it starts right up, no problem. So, we are thinking it might either be the clutch switch, or the electical part of the ignition, but he isn't sure because the car never acts up when he goes to try it. At first we thought it might be the factory security locking out the started, but the security system checks out fine. I was just wondering if anyone here might have any insight or ideas about what might be causing this little problem. Thanks in advance for any input or ideas.

 

When you say security system do you mean VATS? Sounds like a VATS issue to me. Just my $o.o2.

Mike

 

Next time it happens try jiggling the key in the lock to see it anything happens.
Have to wait 4 minutes for system to reset.

 

I would almost bet my paycheck on it being the VATS, my 86 made me crazy with the same thing. I took my digital meter and measured the key pill, there is a section here with all the values and what the tolerance is.
I bought a bag of 1/4 watt 10% resistors from radio shack. I selected a couple of resistors that matched within 5%. at the bottom of the steering column you will find a thin orange cable with a connector. I cut the cable at the steering wheel side and soldered the resistor combo across the two wires. so in affect the ECU sees the resistor.
I have not had a starting problem since, and seeing the the resistor is on the connector I can remove the connector/resistor and the car will not start!

 

It could be VATS, or it could be the clutch safety switch. The contacts in the ign lock wear and if they don't make good connection to the pellet in your key, then VATS won't allow a crank for 6 minutes. Next time it won't crank, remove the kick panel above the drivers feet and find the two wires from above the steering column going to a 2 pin connector. Unplug, insert your key and measure the resistance across the wires from the steering column. It should measure the same as your pellet. If more than 4% off, VATS won't allow a crank for 6 minutes and you have a defective ign lock and it should be replaced. New locks have new contacts that connect to the pellet. If ok, then unplug the clutch safety switch and jump the socket. Measure the voltage on the jumper, it should be 12v in crank position. If no 12v, then you could also have a defective start enable relay. If you jump 12v to the jumper, the starter should crank. No crank, then you may have worn contacts in the starter, but you should hear the starter solenoid click in crank position. At the end of the starter solenoid stroke, it forces two large copper contacts together that switch 12v to the starter motor. These contacts get blackened and pitted and begin to not make a good enough connection to provide starter motor current (100+ amps). The contacts are replaceable.
You can connect a fixed resistor the same value as your pellet across the 2 pin socket (goes to the VATS module) to bypass VATS until you can schedule an ign lock replacement. I don't recommend permanently bypassing VATS because 99% of thefts are done by bashing the column and jumping the ignition.

 

Is there a thermal overload cutout on the solenoid or starter motor ? If so, due to age these may be mal-functioning and a starter/solenoid swap might cure it. I once bought a truck and the starter circuit was routed through an alarm system the put an additional relay in the starter circuit causing an additional spike upon startup. My wife would drive it to the grocery store, come out and it wouldn't start unless she waited 45 mins to cool down. I'd replace the starter and all would be fine for a while, then it would do this again eventually. I changed that starter 3 times before I figured it out. After removing that crappy alarm system, the truck's been on the same starter now for 120k with no issues.

 

Nope, no thermal cutouts on GM starter motors.