So now that winter has arrived I have learned that my Porsche doesn't like the cold. I did a compression (135,135,132,135) and leak down test (10%) so obviously the motor is good. It will run for a second if I use starting fluid but then it dies. So I figured it was a fuel problem. The weird thing is, after trying to start it a few times when I put the key in the on position I can here an electric motor running and after that it will start. Now it sounds like the fuel pump kicking on to pressurize the fuel line but I know this can't be the case because the fuel pump in 944s only kick on when cranking the motor over, not when the key is in the on position. What could it be?

 

Well, my first idea here is that you have moisture in the fuel line that is crystallizing into ice or at least enough to block the flow. A while ago (in a different car) I had a similar issue and adding some fuel additive (like Drygas) did the trick. It's also cheap and couldn't hurt as a first step. I know this doesn't fully address the fact that it will eventually start.... but an easy thing to try....
john

 

I did add some HEET to remove moisture about 50 miles ago. I don't think that's the problem.

 

Kinda thought you would have but figured I'd toss it out there.

 

got the same problem myself at the moment.

 

Why is it only a problem in the cold then? Sticking injectors should present themselves no matter the temperature.

 

well there you are then..... you clearly know more than I do so I'll leave you to sort it.

 

Reading your post, my first thought was to suspect the DME relay.
If after a few tries you hear an electric motor, presumably the fuel pump (fairly loud, higher pitched whining/buzzing sound) with key in "On" but not "start" position, I am thinking the DME relay is getting stuck "closed", which runs the fuel pump, filling the rail, and then letting you start the car.

Try removing the DME relay and fitting a DME relay jumper by connecting these pins:

(details here: http://www.clarks-garage.com/shop-manual/fuel-05.htm)

Let us know if it starts up easier/right away.

 

It was indeed the DME relay (as it always seems to be). Fresh relay solved the problem.

 

I've heard that one should always have a new spare DME relay in the glovebox with these cars!!!

 

Or upgrade to the Solid State version and keep the old one in the glove box? http://www.ftech9.com/new-products/?...tate+Relays%29

 

+1 Spare DME relay in the glovebox. I figured it was the relay after I read your initial post. As you said later, "always seems to be."

PS - Shy away from the cheap relays, they don't last very long. Spend a few extra dollars and at least get a middle-of-the-road one. I'll be going to a sold state soon. Thanks for the link mdnt08!