pcarfan944

I've been having an intermittent starting problem with my 944. I'll go out to start it and it will spin over, want to catch, but not fire. It's done this a few times over the last few months. Half the time I can make it fire by either pumping the gas pedal, or if I leave it sit and come back after a period of time, it will often start again. My mechanic looked at it while it was in one of it's no start modes and said it looked like it was flooded. Note: Every time this has happened it has been fairly cool (below 30 degrees) and only had 1/4th tank of gas or less (I don't think that would matter, but maybe it would?). Leaky injectors? Fuel pressure regulator? Any other ideas?

FRporscheman

If you didn't mention the engine being flooded, I'd say DME relay. Since you have flooding as your problem, I'd say leaky injectors. This doesn't sound like a FPR to me, but it always could be. Also, since it only happens on low fuel, it might be your fuel filter is dirty.

Mongo

cold starts and repeated cranking sound like a fuel pump check valve to me. But, check your DME relay first before resorting to taking apart the hoses by the fuel pump. Good luck.

pcarfan944

Just out of curiosity, if the DME was bad, would the car still start at all? I was under the impression that when the DME goes, it goes; with nothing in-between. This has only happened a few times, otherwise the car starts and runs fine. I'll go pick up a new DME tomorrow and see this still happens.

Mongo

The DME unit does not control the power to the starter. You can turn the key and the starter will crank, however the car won't fire.

Let us know what happens.

pcarfan944

Hey Stig, thanks for the help. I guess my question is, would the car still start on and off with a bad DME? I thought once the DME was gone, that was it.

porschefig

i have a similar problem...I hope this gets figured out!!

PaulStewart

The next time it won't start, wiggle the connector on the DME and see what happens.

dgz924s

If its getting fuel the relay is fine. Dealing with the same issue now and I know one reason is the fuel pressure is down due to a leaky line at the damper. It fires so the ECU and DME relay is good. Fires and runs on and off the injectors are good. Bad injection=no fire up or not run well.

Pressure is the problem so it seems. So you need to look at the FPR/FF/FP, vacuum and lines for pressure loss. Or too much pressure, which ever is the case.

RedlineMan

Well...

You can easily eliminate the fuel pressure idea by hooking up a gauge. Has no one thought to do this for you yet? Check it at cold start, after start, when hot, every condition. Easy.

If you have no pressure at start up, it could either be a leaky injector or the 1-way valve at the pump. The latter does not often fail, though, if ever. If you have a leaky injector, you obviously should also have a lot of fuel in that cylinder.

Electronic components can do anything they friggin feel like doing. The old idea of it either works or it don't does not apply to electronics, just like it doesn't apply to women!

If you don't see pressure abnormalities, I'd start looking at temp sensors like the head sensor. Telling the DME it is hot and metering fuel accordingly at cold start won't work so good, eh?

AZS2

I had a similar problem. My car wouldn't start. When I put the pedal to the floor the car would start. You don't have to pump it, its fuel injected it just needs to be opened or closed because its a matter of air. My problem was the FPR. It was leaking out of the vacuum inlet into the vacuum lines. From there the rogue fuel would get into the intake and cause a rich condition. The only way I could start the car was if I held the pedal to the floor, countering the rich condition with more air. If you get it started, it may not idle well. But if it will idle, pull the vacuum hose off of the FPR. When I did this mine spit gas out of the inlet. Also, if you don't have a fuel pressure gauge, you can pull one wire off one injector and try to start. If it starts and idles this is another indication that your FPR is bad. The idle will obviously be a little rough.

dgz924s

I know in my case I can't go any further until I fix the leaking connection. So pressure test is a moot point for the moment.

Question though is the damper on the return line?

But I am tired of playing games with it so I am replacing the entire fuel system, damper/fpr, lines. Rebuild the injectors too.

83na944

IIRC, the damper is not on the return, just on the fuel rail. It won't be a problem unless its leaking.

THe FPR, on the other hand, generally fails such that the fuel rail pressure is higher than specified. Too much fuel is delivered, the car floods.

Anyway, the FPR is cheap and easy to replace. A fuel pressure gauge will tell you if the FPR is the problem, bu it probably costs twice as much as the FPR. This is definitely the point where you throw parts at the problem.

AZS2

The damper is on the front of the rail and the FPR is on the back of the rail. Return is on the FPR. So, the damper is in front of the FPR in the loop. From what I understand, the damper really doesn't do a enough to cause huge problems.

dgz924s

Leak is on the damper line. Did not make sense that it was a return line the way it was blowing fuel. So now I understand the lack of pressure going to the damper as a result of the leak. Thanks!