Jerry, hopefully those with more knowledge with jump in here. You might want to post on the mail site to get more exposure to others.

As I think about it, our cars are dependant on voltage. When it gets to low, the car stumbles and then quits. Your battery would not have enought power to turn the starter.

Did you ever check the battery level after you were towed in?

Does this seem to happen every session or only during longer sessions?

When it happens, did you charge the battery afterwards?

My thinking with these questions is trying to see if it could be a charging problem with the alternator to battery system. Is your system charging normally?

I have one of those "smart" chargers that tell me the battery voltage and the % of full charge. Your symptoms sound like mine when my alternator quit and I didn't notice it until it started crapping out on the track and then quit.

Big Dog

It could well be, but the car would start up after some period of rest (without a recharge). When I measured the battery I took out of the car it measured 12.7V (which should have been enough to kick the car over).

Hey Jerry,
Another guy seems to have a similar problem. Here is what's happening on Rennlist
forums.rennlist.com/rennforums/924-931-9...t-start-problem.html

Difference is he is getting the starter to crank.

My problem appears as when hot the starter will not spin therefore not attempt to start the car. Symptoms very like a run down battery but after cooling the same battery has been able to start the car.

Suspects are:

1) Battery cables to starter and alternator
2) Alternator not charging
3) Starter heat soaking
4) Ignition switch

Jerry,
Did you test the starter both in both cold and hot state?
I assume your getting no spark at the coil after it dies?

I haven't tried this on the 944, but have on another car when stranded way out in the boondocks.

Same description, lost spark after it warmed up and then starter no crank, but plenty of voltage in the battery. I ran a hotwire straight from the positive battery to the + post of the coil to bypass the DME and everything that might send an interrupt signal, and since the starter was still frozen, push started the car and to my surprise it actually started! We only ran it like that enough to get home.

I still don't know why, but I ended up replacing the starter and solenoid and it was cured. I guess the ignition circuit was routed through the starter to the coil?

Haven't done any testing yet except putting a DVM on the battery when it had a problem after being towed in. Strange thing is that adding a jump box allowed it to start. So on Sat after the failure I put a new full size battery in place of the lightweight. Problem happened again on Sunday with the new battery within the day.

Still need to do some dedicated DVM work which will take place on this weekend