944tr3roverp4

Hello everyone; I have just bought a 1985.5 944NA (obviously NA) from a total 944 fanatic who had owned this car for 19 years, never winter driven. It has come up with a non-start fault. If I drive the car for 2-5 minutes and then turn the engine off, then wait for half to one hour, the car will not start until the next day. If I drive it for 15-20 minutes, I will not have the same problem and it will re-start all day long, as many times as I start it.

When the fault started, I had someone watch a fuel pressure gauge that the PO installed under the bonnet. Loads of fuel pressure, so am guessing ignition???? Any ideas what I should be replacing, in the hope of curing the problem?

Many thanks, Tim

Legoland951

If it is completely random in when the car fails to start and how long it stays not starting, it is likely electronic such as the DME relay or your crank angle/reference sensor. Check to see if you are getting spark next time you have a no start condition.

944tr3roverp4

Thanks very much for the reply. I'm sure there can't be spark, as there is so much fuel pressure when it's on-fault, but I will check for spark to be double-sure. Someone else had suggested the DME relay, so I may change that. The crank angle/ref sensor was renewed a couple of years ago, apparently, but that doesn't mean it isn't faulty now. Thanks again.

944tr3roverp4

PS Legoland951: I just looked up the DME relay and what I read initially is that if it's faulty, it will not allow the fuel pump to operate. Is that correct? It's just that I appear to be getting lots of fuel pressure.

Wisconsin Joe

Start with basic diagnostics.

When you get the no start, are you getting spark?

Are you getting injector pulse?

The answers to those 2 questions will take you a long, long way towards getting this resolved.

mikehayes

I second Joe. Just because you have fuel pressure doesn't mean your injectors are firing the fuel into the cylinders. Check if you have spark by pulling a plug and grounding it (while plugged in) to the valve cover while cranking. While the plug is out you can also look into the cylinder and see if you can see gas squirting into the cylinder.

Wisconsin Joe

You can also use an inductive timing light to check for spark.

A noid light will tell you if you have injector pulse.

Rayce

H all. I am new here and have a very similar problem as Tim, mine is 85.5 944 non turbo, it usally starts cold (some times) if i drive it a short ways it will start again, if it gets warmed up it wont start for a while and no tach bounce in the no start times. I dont like just changing parts till the problem go's away but I have to in this case. new DME relay installed, and now I want to try the referance speed sensor. can anyone tell me if the crank position sensor and the referance /speed sensors are the same parts? I have looked all over to answer this question and found conflicting results. I just want to order the one speed sensor to try it.

Thank you
Rayce

Legoland951

Yes they are the same part. All you have to do is switch them.

Rayce

Thank you for your reply, I have just ordered two new ones, I will post my results after I install them

Rayce

just an update on my sensors, I ordered two new sensors for mine, first I changed the speed sensor out, and I found no change at all, still only stared intermittently. So then i replaced the crank position one, no start at all now, put old one back in no start at all, put new one back in no start at all. so I pulled the DME board from my floor kick panel and tested the pins 25/26 and 8/27 low resitance. so I ran a wire from the housing of the DME right to the battery ground. starts and runs perfect so far, started and stopped it many times fired right back up again. I am going to drive it around with the extra ground on it for a while and see how it goes, if its good i will permanently install the wire

Thanks for everyones help
Ray

Rayce

My update on this problem, my starting problem seems to be gone with adding the ground wire, i installed it more permanently and i have been driving it around with no problems, i am going to take it on a long road trip now and actually feel I can rely on it. this is a great feeling.

Thanks
Ray