Fuel delivery

[Bonymaenjack]

Evening
Sorry to start another thread but this is slightly different in terms of the problem I'm experiencing , my
325 I is difficult to start . I've changed the FPR due to my suspicion that the old one had failed. It was tested with an inline pressure gauge and showed no pressure feeding the fuel rail unless I clamped the return feed on the FPR then it would move up to 40+ PSI but wouldn't alter either way when opening the throttle nor when removing the vacuum pipe from the FPR as most tests have shown as being a reaction .
I've replaced the FPR and left the in line gauge attached , I've run the pump by removing the fuel relay and bridging across the contacts to simulate the engine running , the pressure only slowly rises to 1 bar and holds there , I start the engine and open the throttle with no rise in pressure neither does it alter when removing the vacuum pipe form the new FPR although there seems to be a lot more suction when removing the pipe than when the old FPR was fitted. The only way I get the pressure to raise to its specified operating pressure is by clamping the return pipe, this indicates the FPR is faulty or does it ?
I also suspect an injector is leaking but I haven't started the car for over a week and when I removed the FPR from the fuel rail I had a back feed of petrol out of the orifice where FPR connect , if I did have a leaking injector wouldn't the rail be empty of fuel ?

[Brianmoooore]

If the pump is capable of developing the required pressure and flow, then it's the FPR that brings that pressure down to the required value. The small reference pipe from the manifold to the regulator reduces the pressure shown by a gauge to maintain 3 bar across the injector, given that the business end of the injector is inside the manifold in an area that is at a pressure less than the outside air. If you used a differential pressure gauge, with one of its pipes inside the manifold, the pressure would stay at 3 bar all of the time, just as it should if you disconnect the reference pipe to the regulator.
An injector that leaks at 3 bar will leak less as the pressure drops, and the leakage could drop to zero long before the fuel pressure does.

[arrisbmw]

sounds like you fuel pump is not delivering enough pressure have you changed the fuel filter ?
any leaks in the line from tank to the fuel rail ?

[arrisbmw]

you do realise in normal operation , the live power to operate the switch in the fuel pump relay comes from DME main relay red and white wire , but this does not operate the fuel pump relay , its controlled by grounding out by the ecu brn and grn wire.

[Bonymaenjack]

sounds like you fuel pump is not delivering enough pressure have you changed the fuel filter ?
any leaks in the line from tank to the fuel rail ?

I replaced the fuel filter and the fuel pump last year as the car had stood for 11 years or so then I replaced the fuel filter again last month., the tank has been emptied and refilled a number of times. I'll have to get underneath to check the fuel delivery pipes as I'm getting a strong smell of fuel and I'm not getting any further with finding out what's wrong ,
I've just replaced the FPR with a new one and now the idle hunts for about 3 or 5 times before settling down to around 800 rpm .Its running rich but the OBC consumption around town shows 20 mpg