bad fuel pump??????

[custom e30]

my set up

1988 325i Turbo
holset hx35w
36lb injectors
15psi
fmu
tre performance 255lph pump



issue - when cold start, the car starts and runs just fine, after about 10 miles of driver ill notice my wide band getting leaner at idle, car starts to have rough idle,

ive replaced fuel pump bracket, all new wiring, checked the intire fuel system for leaks...

today it did the same thing again???? HELP!!!!

[custom e30]

im guessing my pump could be going bad, but i went ahead and ordered a new fuel pump relay and fuel filter for fun, any help, thanks

[Earendil]

If you want to eliminate the pump, buy a fuel line pressure gauge, and stick it near the rail on the line going into the fuel rail. If the pressure is good, and doesn't drop under load, your pump and filter aren't the problem.

If the pressure is bad at idle, but doesn't drop under load, it's probably your FPR.

[custom e30]

im gonna do it right now

[SmokeE30]

You need to t a fuel pressure gauge into the car to see what is happening when your AFR leans out. Without doing that you can't know for sure if it's even a fuel issue. It could be vacuum leak problem. Things heat up and expand making gaps larger allowing more air in once warmed up. Check fuel pressure and check for vacuum leaks then report back

[MR 325]

Checking fuel pressure is a good start for sure. You don't really need anything bigger than a stock pump even with a boosted engine. What you need is the right engine management and tuning, not a bandaid system with a FMU. Trust me, been there done that.