mikebarton

86 944 turbo. cars runs perfect, except that it cuts out for no reason at idle or while driving. I had the dme relay replaced 200 miles ago, and the problem was gone. NOw it is back again. First it would start then idle(smoothly, no rough idle) for a minute then just cut off. Now it wont even start at all. just turns and turns. Can the new DME be bad already? do they go bad that fast soemtimes? Do i have other electrical things i should rule out before spending 30$ on a relay that i just replaced??? getting pissed with this freaking car!!!!! any help before i waste 120$ getting it towed to my porsche mechanic is greatly appreciated.

Tom M'Guinn

Have you checked for spark? Pull a plug wire and see if it arcs to the head when you crank it(don't shock yourself!). If you have spark, then you've ruled out the relay and a number of other issues.

mikebarton

what do you mean see if it arcs? and where do i hold the wire too? against the head? thanks for your help! i appriciate it......going nuts over this.......

eclou

there is a way to jumper the DME relay to make it work. Do a search on DME relay. I also experienced this once when the O2 sensor wire melted against the exhaust and shorted it out (kills the fuel pump)

mikebarton

ok, tried the dme test wire, its not the dme.....what is happeneing is somehwre between the fuel pump and the injectors i am not getting fuel into the cylinder. the car runs for like a minute then stalls. ( seems like it is stalling when whatever is in the fuel line is used up.) what can i check for not keeping fuel pressure? i hear the fuel pump running. could it be the Fuel pressure regulator????

Landjet

How old is the fuel filter by the tank? I took the filter off and blew into it backwards after having an idle/acceleration problem on my street car. You could not believe all the crap that came out. Car was much better after that. It's a pretty easy check to make.

Tom M'Guinn

Since it's easy, you might start (with the motor not running and ignition turned off) by pulling off the vacuum line to the fuel pressure regulator and making sure (a) that the vacuum line has no gas in it, and (b) that the fuel pressure regulator holds vacuum without leaking. Confirm the latter using a small hand vacuum pump (MitiVac) like those sold at virtually all auto parts stores.

If that checks out, to confirm it's a fuel delivery issue, you can attach a mechanical fuel pressure gauge. I use an off-the-shelf fuel pressure gauage like those sold at all the national auto parts chains, connecting it using a piece of fuel pressure hose and hose clamp on the end of the fuel rail (make sure it is a tight fit --3/8" ID is what I use I believe -- it 'screws on" to the threads at the end of the fuel rail and then clamps tight).

You have to remove the lug nut at the end of the fuel rail to attach the hose. There is a little steel ball bearing in the nut on the end of the fuel rail -- just make sure that doesn't roll into a storm drain when you take off the nut, and be sure to put it back when you're done. Have plenty of towels under the nut to catch the fuel that will come out and be sure not to start until the exhaust is cool to the touch. The manual says to depressurize the fuel system first. Be sure not to start until the exhaust is cool to the touch. Make sure it is not leaking when you start the car and only run the motor as long as needed to run the test. Have a fire extinguisher with you too -- better safe than sorry.

mikebarton

ok, just put a new fuel pressure regulator on. that wasnt the issue. IF i let the fuel pump run for a few minutes(while car is not running) the car starts and runs for about 2 minutes then cuts out.......so what is happeneing is the pump is getting enough fuel pressure to keep the car running for a few minutes but is not sustaining pressure. SO it must be my pump not working 100% or a clogged fuel filter? what do you guys think

Tom M'Guinn

Have you checked the pressure? Either way, the filter is easier and cheaper to replace (and easier to find on saturday), and you probably want a new one anyway if you end up installing a new pump.

mikebarton

ok idiot statement, ready? where is the fuel filter? i cant find it.........is it underneath near tank? i dont have hose clamps either, ****

Tom M'Guinn

yeah, it's in the back by the tank. If you back it on to ramps, you can get to it without too much effort. If you have a tranny cooler, that can get in the way a bit.

Dave951

Here is a picture of the fuel filter location. Taken from under the passenger side rear (Left hand drive)

Landjet

FYI if you do change the fuel filter it is good to somehow mark the date and mileage on the new one so you can see it after installation, scribe, sharpie, small paint brush. I also do this on the top of my oil filters before I put them on. This way if I misplace the paper copy I can take a quick look a check the last change date or mileage.

mikebarton

well well.......just looked at the fuel filter, IT looks like it is the original one........corroded and same color as everything else under there, plus the bolts you can tell have not been loossened, no a mark on them..........wow.........i think i may have found my issue.............could fuel filter really cause this though? car has 84 k miles. i guess it may be slowing fuel down and thus causing car to stall............

Tom M'Guinn

Timing belt cover too!