Won't re start when hot?

I was wondering if any of you have experienced this problem?
I own a 92 512TR and as of late the car will not start after it's been driven and warm. The car always starts in the morning, but after a drive, when the engine bay is hot it will not turn over again? Now all the dasboard lites come on, but it doesn't crank, basically nothing happens, unless I jump the terminals on the solenoid and just give it a jolt. After doing that, it always starts again immediately???
What does this mean, a bad solenoid, bad ignition switch, bad starter???
Thanks
Paul

 

I think you've got the right suspects listed in the right order of probability. Many reports of "nothing at a warm restart attempt" for TRs that turned out to be related to a flaky solenoid (that would always seem to work well at cold restart). Do a search on "TR solenoid" for a lot of previous background/discussion.
The usual strategy would be to measure the voltage on the "start command" line coming into the solenoid when you turn the key to the start position -- if it goes to something reasonable (9V~12V) that would rule out the ignition switch. The sequence is completely serial (solenoid fires then starter motor runs) so until you've got the solenoid firing (i.e., the solenoid plunger actually moving when you give "start command") no reason to suspect the starter motor.

(Of course, if you're stuck somewhere when warm, {key "on" and gearbox in neutral} try touching a jumper from the +12V terminal at the solenoid to the "start command" terminal at the solenoid -- usually works.)

Good hunting...

 

I've mentioned this a time or two relating to similar problems, but It sounds like you have voltage drop. (Very common in these cars.)
Bosch solenoids "soften" up over time and heatsoak limits their ability to pull in the plunger when a little sticky.
A work around (that i have done on many other cars) is to install a relay at the starter motor. (Essentially the Solenoid is a big relay in itself).
With your description of jumping the solenoid and it working OK from then on, I would defintly start with a relay.
You could probably replace the solenoid which may fix it for a while, but I imagine you will run into the same problem again before too long.
If you need help on how to insatll a relay let me know. It should be a $5 fix.
Cheers!

 

My ex-348 did the same thing and it turned out to be a faulty ground, which was difficult to locate but easy to fix once found.

 

I did exactly this on my 348 spider and it works perfect now - the guy who looks after my car said this is not uncommon.

Cheers
Kevin