EAGLESTONE
New member
hi can any one help old girl wont start no pressure in the fuel line just dribbles had new fuel pump and filter changed relays any suggestion please
fuel problem help
- Thread starter EAGLESTONE
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EAGLESTONE
New member
someone said there should be 4 bar pressure when u undo nut at end of fuel linemine just dribbles
alwigley
New member
Have you bypassed the DME relay to prove you are getting power to the fuel pump ? 3 way jumper cable across the 3 large pin (sockets) performs a total bypass of the relay and should power up the fuel pump even with the ignition off (hence disconnect when leaving the vehicle) and you will hear it whirring away. Clarks Garage gives more details of how to do this.
Faulty FPR tends to starve the engine of fuel as they normally fail closed, then the DME detects too high pressure across the fuel rail and shuts down fuel pump - quick check is to disconnect one injector from the harness and see is she will start - this apparantly fools the DME into thinking the fuel pressure is lower. Will run like a dog on 3 cylinders, but if she runs you may have found the fault. FPR should be ineffective if you have removed the nut from the end of the fuel rail, BUT in order to test this properly you must bypass the DME relay otherwise I think it shuts off the fuel pump, so you may be getting a false result.
Not sure where/how you have started tracing the fault, but the Porsche workshop manual gives a full guide to trouble shooting problems with the fuel injection system, and a few hours patient work with a multi-meter can save you a lot of money in replacing parts in the hope of a fix [
].
Faulty FPR tends to starve the engine of fuel as they normally fail closed, then the DME detects too high pressure across the fuel rail and shuts down fuel pump - quick check is to disconnect one injector from the harness and see is she will start - this apparantly fools the DME into thinking the fuel pressure is lower. Will run like a dog on 3 cylinders, but if she runs you may have found the fault. FPR should be ineffective if you have removed the nut from the end of the fuel rail, BUT in order to test this properly you must bypass the DME relay otherwise I think it shuts off the fuel pump, so you may be getting a false result.
Not sure where/how you have started tracing the fault, but the Porsche workshop manual gives a full guide to trouble shooting problems with the fuel injection system, and a few hours patient work with a multi-meter can save you a lot of money in replacing parts in the hope of a fix [
].
Sounds like fuel pressure regulator?
Mike
Mike
Correct me if I am wrong, because I have been solving fuel problems on 924 Turbos which are totally different, but doesn't the FPR work on teh return line to the tank? therefore, if it fails closed, it means you get excessive presure in teh fuel rail?
Anyway... bypassing the DME relay means the pump should run with teh ignition on - if it is an early car, there is still teh fuse in teh auxiliary fusebox (I THINK it is No. 2)... I check voltage at the pump itself, and proved my problem by connecting the pump directly to an external battery at the back of the car (I had a number of corroded connections at both fuseboxes - cabrio - says it all) Check the voltage with the pump connected/supposedly running - with the pump disconnected the volt meter will happily show 12v even though it won't flow sufficient current for the pump if it is a dodgy connection.
Using the above methods the valve on the end of the pump means you SHOULD be able to get fuel up to pressure in the fuel rail without having to start the engine. If you can't, then it suggests an Non return valve or FPR problem.
After that, I would suggest you are looking at a possible blocked fuel line... disconnect the pump and fuel rail and blow through with an airline.
Hope this helps, Tref.
Anyway... bypassing the DME relay means the pump should run with teh ignition on - if it is an early car, there is still teh fuse in teh auxiliary fusebox (I THINK it is No. 2)... I check voltage at the pump itself, and proved my problem by connecting the pump directly to an external battery at the back of the car (I had a number of corroded connections at both fuseboxes - cabrio - says it all) Check the voltage with the pump connected/supposedly running - with the pump disconnected the volt meter will happily show 12v even though it won't flow sufficient current for the pump if it is a dodgy connection.
Using the above methods the valve on the end of the pump means you SHOULD be able to get fuel up to pressure in the fuel rail without having to start the engine. If you can't, then it suggests an Non return valve or FPR problem.
After that, I would suggest you are looking at a possible blocked fuel line... disconnect the pump and fuel rail and blow through with an airline.
Hope this helps, Tref.
My experience is on 1980's Lancias with similar injection system, and I had weeks of hassles with one car doing all sorts of things before stopping entirly - low fuel pressure - was eventually found, regulator replaced - 125 bhp back!
It was the last thing in the diagnosis book!
Mike
It was the last thing in the diagnosis book!
Mike
EAGLESTONE
New member
thanks very much took injector off as suggested started straight away on three replaced the injector runs great havnt turned off yet nice to here it running if i replace fbr should it clear where would i find it thanks again for help
EAGLESTONE
New member
thanks everyone 4 help
Hi - Great - FBR should be available from Bosch centre most motor factors, Porsche Centres and Indies in a couple of days max.
Mike
Just re read post FPR probably is dead and is mounted on fuel rail - exactly where depends on the rail (there are at least 3!)
Mike
Just re read post FPR probably is dead and is mounted on fuel rail - exactly where depends on the rail (there are at least 3!)
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