Porsche Enthusiasts Club Forum

I have a strange one 87 944 started it up on Sunday backed it out of driveway which takes a little of wiggling so car had been running 5mins or so got 100yrd down road it just stopped as if out of fuel .Refused to restart. Plug out, big fat spark no sign of fuel put £20 in day before so not empty tank (but close).Mate and I got it home. Local friendly garage i use picked it up and tried normal faults including removing after market isolator .After some discussions easy start was used just enough to start it and it did and then ran under its own steam ,would restart every time until the morning when only easy start will work its magic again.so after all that what do we think problem is ..Fuel regulator? Fuel damper? something else? Pump runs well and the filter has been changed .

Possibly a faulty DME relay - you can hard wire it to check that the fuel pump comes on

Could also be a dodgy fuel pump or fuel pressure regulator - in that case you want to check for the pump turning on and then that you are getting the right fuel pressure

http://www.clarks-garage.com/shop-manual/fuel-05.htm

DME changed for known good one still wouldn't start unless easy start used. Pump runs and seems to have good flow. Could it be venting problem? New regulator on its way.

Once it’s started does it run ok?

Will it start on only 3 injectors plugged in, the engine needs to reach 200 rpm before the fuel pump is switched on by the ECU

yes once easy start has done its magic it will start over and over again unless left for couple of hours .

You need to run through the troubleshooting procedures to narrow it down, a good one here on Clarks Garage -
https://clarks-garage.com/shop-manual/fuel-16.htm

You need to check fuel pressure with a pressure gauge and perform a leak-down test, also check the injectors like Waylander said.

When was your fuel filter last changed?

Video here also on fuel troubleshooting on the 944 -

For your info,

The fuel pressure should be maintained in the rail for at least 2 hours

I would spend £19 and buy a new non return valve for the fuel pump
It’s used on all these L jettronic systems, Volvo Mercedes, Porsche and others

Just Google Bosch 044 non return valve,

well a new regulator seems to have fixed it. (may carry tin of easy start for awhile) Although I do like the idea of fuel check valve so will also replace that to.
thanks for the help guys