Porsche Enthusiasts Club Forum

Hi All,

Any help would be appreciated as I'm having to commute by buses

My 87' 944 lux cut out at the weekend when driving up a slip road. It restarted but only traveled 50 yards until cutting out again. I got it back home with help from the AA flatbed. It will start up fine, idle for 10ish seconds and cut out, can be started again straight away with same outcome. I have 1/4 of a tank petrol left btw .

The AA man did some diagnosis:

Tried my old DME relay - no change

Checked for spark - has spark

Idled with the air filter slightly open then when cutting out sprayed a "petrol aerosol can thing" in the through the air filter into the inlet manifold - Kept the engine running!! - so we thought fuel delivery prob.

Checked power to the fuel pump when cutting out - power still remains (so not an ECU or DME prob).

Ran independent power to the fuel pump to rule out power prob - engine still cut out, pump making a lower pitched noise than the normal higher pitched noise when working correctly.

Constantly tapped the fuel pump when idling - no change, cut out

AA man says I need a new fuel pump.

The way I see it, the problem could be:
1. Knackered fuel pump
2. Blocked fuel filter
3. Blocked fuel pump suction strainer
4. Dodgy fuel (but runs good when running)
5. No fuel -this would be embarrassing, but gauge shows 1/4 tank.
6. Something else...

When I get a few hours of daylight I was thinking of checking for any blockages first before changing the pump, as the clarkes garages guide says that these pumps are normally reliable.

Weird thing is I had the same problem a couple of years ago, turned out to be the ECU, a second hand one fixed it.

Any thoughts or tips?

Rich

Maybe fuel pressure valve, seems to ring a bell from a previous posting

Cheers for that, the other post mentioned these could be bought on ebay cheap, will have a look.

Had similar problem with my 87 lux. Turned out to be fuel pressure regulator.
About 60 quid delivered from Porsche Shop. Clarkes website has a diagnostic for it,
Good luck with it!

Take pump output off & check it pumps! If you have a decent ammeter see how much current the pump is pulling. Lots of these pumps are 20+ years old now & starting to drop pressure. When did it last have a fuel filter?
There is also a filter on the outlet of the tank which can block.

Thanks for all your responses, Quick update:

I followed the Clarkes diagnostic for a faulty fuel pressure regulator:
"If you have a condition where the car will not start or starts and almost immediately dies, try disconnecting the wire for one (1) injector. Attempt to start the engine. If it starts and continues to run, the fuel pressure regulator is likely bad. Bear in mind that running on only three cylinders, the car will run very rough. By disconnecting one injector, it reduces the current enough to keep the injector drivers from shutting down."

I disconnected the electrical connector for injector no. 1 and she kept running on 3 cylinders, reconnected the injector and she cut out again after a few seconds.

So I'll order a new pressure regulator and try to fit. Fingers crossed my bus riding days are over soon

Ill let you know how it goes.

Rich

Jim, the fuel filter should have been changed about 2 months ago with the last service.

Hopefully, it's the FPR. Has anyone had any experience of replacing the fuel pressure regulater? Im a bit worried about having high pressure petrol spraying everywhere! Guess I need to find lots of rags

I changed FPR on mine, it took about 10 mins. Didn't spray everywhere when released.
I would definately wear glasses though just in case and have rags available as some petrol did dribble out.

The new FPR fixed it!! Thanks everybody for helping me out

Yep, pretty simple job and didn't get any spray either just a few dribbles.

I'm hoping this may have made cold engine starting quicker as well because over the last year or so its had to turn over at least 6-7 times before starting, used to start first time every time. If not I read about another valve that can fail (maybe fuel check valve?) that can cause these symptoms.

Time to sort my membership out i think, this forum has been invaluable to me over the past few weeks. I'm just glad I don't have to navigate the Bristol bus routes anymore.