Intermittent no start

[demon]

I have a 1984 targa and having a weird issue. It, sometimes, doesnt start. Most of the time it starts up and runs fine. test drove it today 4 different time and shut it off and started it back up at least 5 times every time i drove it and then went out and it wouldnt fire up. Weve changed the 2 crank sensors and the DME relay. cleaned all the grounds. When it doesnt start , the tach doesnt bounce. But i can turn the key on and off trying to start it and it might start the very next time. Any ideas?

[88911coupe]

This almost sounds mechanical with the starter switch? Just to clarify...are you saying it does not crank over at all when you turn key to "start" position? Ischmitz is the genius in this area...he fixed me up few years ago when my DME control unit was buggy. Also later I had one of the engine sensors that would get out of spec on occasion and deliver resistance level out of range. That was very confusing since I assumed they either worked or they didn't.

[jlex]

That was happening to my '88.... wouldn't crank at all about 20% of the time. Replaced the ground strap and problem is 100% solved. $10 part/easy repair.... try that first. Starter demands lots of amps. Not quite sure from your post if it's no start or no crank.... if it's cranking, forget what I said!

[Walt Fricke]

CHT?

But maybe the tach which didn't bounce points to the start position of the ignition switch failing? You can replace the electrical switch part without having to remove the lock part.

[88911coupe]

Maybe run a starter switch bypass to see if that helps? I set one of these up when I was having issues then figured out what the problem was. I know there are some threads on it if that might help troubleshoot.