Tony951

Try swapping out your DME box with a known good one - your intermittent cutout could be related to a bad solder joint on the DME board (ie components or connector joints). I had this same issue on my 88 951 and after replacing DME relay, coil, battery grnd wire, alarm system, etc I finally sent my DME to systems consulting for a rebuild ($375, 3yr warranty). Problem fixed.

Landjet

Mike as far as your question can the fuel filer cause this? What can happen is the debrie (if there is a lot in the filter) will settle on the bottom of the filter when the car is not in use. When you run the car and fuel is pumped through the filter it can pick up the debrie a little at a time and start closing off the filter. This may not be the problem with yours (it was with mine) but if you think the filter is original it is overdue for a filter change anyway and this will be the cheap and easy way towards trouble shooting that part of the issue.

Rich Sandor

Do you have fuel pressure at the rail?

Pull the entire fuel rail out of the car, with the injectors attched, and crank the ignition.

Do the injectors fire? If they are not firing, you have one of more of the following electrical problems.

1: dme relay
2: dme box
3: ref sensors
4: injector harnesses

Tom M'Guinn

http://napaonline.com/MasterPages/NO...ressure+Tester

mikebarton

rich, you can pull the injectors out that easily? attached to the rail as well? so you dont think it is my filter or pump? if my injectors were not working then it wouldnt run for a few minutes before it stalls. you know what i mean?? suggestions? its not the dme relay, or fpr. again, anytime i let the fuel pump run for a few minutes without starting the motor to let pressure build up, it starts right up and runs great until that fuel get used . You can literally hear the car after like a minute just start losing gas and stall as if its running out of gas, which its doing.

Rich Sandor

A frayed wire in the injector harness or going to the fuel pump could cause intermittant fuel delivery.



In my case, the wires beneath the thick boot at the root of the fuel injector harness were actually frayed INSIDE of the harness itself. (which looked fine from the exterior!)

Always troubleshoot systematically, and then start replacing the cheapest parts first. Since these cars are 20 years old, the most logical and cheapest thing to test first is the wiring and grounds. You'll be horrified at how bad the wiring in the engine bay is on these cars after 20 years!

mikebarton

rich, even if my car runs for a few minutes perfectly smooth, after letting fuel pump run for a few minutes without starting car, you still think it could be my injectors? and not just a pressure issue? ALSO, does anyone know if a fuel pump either is working or not with no in between? in other words can the pump be running , but not fully enough to keep pressure up?

DHC8FO

I hate to say it, but I had an issue simular to this and had to replace the fuel pump, my mechanic also advised that I should replace the relay at the same time, as his experience was that they often are not far apart on failure. If you can swap with a known good pump, you coul eliminate this. Since you know the problem is delivery, it could well be the pump.

mikebarton

thats it, i have had it,,,,getting towed tommarow to my porshe mechanic.free anyway to tow, i never use my AAA. I loooked at that fuel filter and now i see why most dont ever change it. what a **** spot to have it in, esp when you car has the tranny cooler on it.............screw it, my sanity cant take trying to fix this issue myself. id rather write the check at this point................pisssssssssssssssssed

DHC8FO

Let us know how it works out.

mikebarton

well had the fuel filter replaced and problem solved,,,,,UNTIL i got about 30 miles on car. now it is doing the same **** again. the fuel filter was the original one. believe that? my porsche mech said he couldnt even blow through it. BUT guess what, car still acting up........i give up. i wonder if the injectors get clogged while driving now b/c so much sediment in fuel system. I dont know what to do. when the car runs, it runs like a gem. i mean perfect and strong. it just cuts out out of the blue. i wonder if the dme chip is bad? anyone ever see them go bad?

skene

I feel your pain man. My car does the same stuff on occasion. Pretty much only after things get hot in the engine bay, like sitting at a light or trying to start the car after it's been driven in the last hour or so.

I'm slowly replacing all the electrical connections trying to find the problem. Every boot connection that I've taken appart has the wires about to break like what Rich Sandor showed. This includes one reference sensor, DME temp sensor, and some of the injector wires. The injector wires, knock sensor, and other reference sensor are next to go.

When old rusty wires get hot they often don't conduct well, so that's why I'm leaning towards an electrical issue. That and I've already replaced everything else.