525i fuel pump

[grave77]

Does the 525i fuel pump work on the 535 engine? are they the same or the 535 delivers more pressure than the 525?

how about installing higher pressure pump would it work better in some cases?

[Bellicose Right Winger]

Looks like both use fuel pump PN 16 14 1 181 354.
Fuel pump needs to be able to deliver a volume greater then max injector consumption rate and at a pressure higher then fuel pressure regulator setting. Fuel pressure is then controlled by Fuel pressure regulator, by partially blocking the return to the fuel tank.

Paul Shovestul

[grave77]

well .. that brings me to something else which is the fuel pump pressure. if the reguilator doesn't seem to work propperly even if replaced then I think that the pump is lacking pressure. is this assumption true? since I have replaced my exploded original pump with a second hand 525 pump it stopped the choking at high RPM. now it's not idleling well untill I squeez the return pipe from the regulator and it loses torque when I reache over 4500 RPM as if there is no enough fuel pressure but it doesn't choke. do you have any idea about the reason?

[Bellicose Right Winger]

Your assumption is true, if you have a good regulator and you still have low fuel pressure then the pump is probably bad. The only way to know for sure is to install a gage and check your fuel pressure. There have been several posts here about making fuel pressure testers from hardware store items.

So you've got a new fuel pressure regulator and a used 525i fuel pump. If engine runs well at wide-open-throttle, then I doubt fuel pressure is the problem. The fact that you can improve the idle by squeezing return hose, which raises the fuel pressure and richens the mixture, may indicate that you've got a vacuum leak.

Paul Shovestul

well .. that brings me to something else which is the fuel pump pressure. if the reguilator doesn't seem to work propperly even if replaced then I think that the pump is lacking pressure. is this assumption true? since I have replaced my exploded original pump with a second hand 525 pump it stopped the choking at high RPM. now it's not idleling well untill I squeez the return pipe from the regulator and it loses torque when I reache over 4500 RPM as if there is no enough fuel pressure but it doesn't choke. do you have any idea about the reason?

[grave77]

Good point!! I'm impressed ... what usually causes vacume leak? any frequent place in the engine? I can notice that squeezing the return helps the ideling as you said. and I also noticed that the economy meter doesn't reach to the minimum when I open the throttle to the max when I'm in high speeds.