1983 944 intermittent starting

I've had this car for 3 years, its been in the shop most of the time. This car runs great, but once in awhile it just won't fire. I had it home for 3 months, trying to fire every week or so with no luck, was going to have it towed to another shop and have it checked out. I checked to see if it would fire, it wouldn't, it just turned over and over. I pushed the car out of its spot in the shop, got in and fired it right up. Drove it down to the shop where they had it for 3 weeks and could not get it to not fire again. Until one of the guys took it to pick up some parts and got stranded. Same thing, just turns over and over, no fire. They got it back to the shop and it fired right up again.
This is very frustrating. I would like to drive the car, but I can't take the chance of getting stranded again. Tow bills are killing me.. Any ideas on what this could possibly be?

Does the Tac bounce when you try to start it (when it wont start) if it does bounce, then likely it is the DME relay. If it does not move it is your reference sensors. It could also be a loose connection to the relay or the security system. Since it happens after the car has moved it seems likely it is wiring, but the relays can act the same way. I would change the DME and see what happens.

I'll just go buy a new DME relay and try that. 25 bucks is a quick cheap check, as far as the DME control unit, It sure would be nice to know someone that you could borrow theres to see if it fixed it. anywhere from 500-700 bucks for them bad boys. That would be something to spend that and not fix the problem..

The DME relay is a good choice, its always good to have a spare. If it is no help check this link for an ECU, I have a spare one of those also, just cause I got it at a good price.
http://cgi.ebay.com/ebaymotors/PORSCHE-944-Motronic-Injection-brain-nice_W0QQcmdZViewItemQQcategoryZ33553QQihZ005QQitemZ150078139762QQrdZ1QQsspagenameZWDVW
I guess this means you do get the tac bounce on the no starts?

Just to add the ECU on the link is not exactly what you need but the contact info for the seller is in the add and they probably can hook you up for a decent price on one that will. (if you need it)

Thanks for everything. No, i didn't check yet, its still down at the shop parked. I need to get it back home next week.
Now that ECU on ebay, from what I have read, aren't ECU's for 83-85 swappable? Maybe I'm wrong....

The 83-85 EU are, but would have to check part number to be sure. I'll see if I can look that up for you latter today.

From what I see,  0 261 200 015 944 618 111 01, is the part number, and it matches the one on ebay.  But heck, what do i know. I'm a Ford guy trying to work on a Porsche..
Thanks again for all your help

Thats the only part number I show for those years, so it should work in your car. The DME relay will likely fix your problem, but an ECU for a spare and/or a back-up fix might be a good idea. If the price stays right.

I hear ya, Thanks for the help, i'll tell you what I find..

Just to tell you, kinderrich is an awesome resource to have with problems. I have been trying for 2 years and $800 dollars later to try to get this problem fixed. It looks like it was just the DME relay. $25 part. Boy does that piss me off and make me happy at the same time.. I just want to say I appreciate the help greatly.
 
"Alot of people can play violins, but not too many people can play it great"
 
We have some great violin players here.. you all know your stuff..