hey folks, I'm troubleshooting a power issue happening to my 323i, and have managed to only confuse myself more. It's not clear that I am pursuing just one issue - the car sat for a long time, so multiple failing components could be combining in weird ways.
The symptoms:
- very down on power, minimal throttle response. I can barely get it above 70mph, and opening the throttle by hand in neutral makes it bog for a second before it spools up
- fuel rail loses pressure very fast. I put a gauge inline to the cold start injector - it goes down to 0 psi in several minutes, you can watch the needle drop.
Fuel pressure behaves kind of strange in addition to the rail purging - with the car idling it stays at the regulated 2.5bar with some vibration. When revved, it dips slightly, and drops by .5bar when the throttle is let go and the engine winds down off power.
What I've tried (mostly related to getting the fuel system to work right as a precursor to chasing the power loss down):
- replaced all small vac lines, inspected large ones
- verified AFM flap moves freely, but haven't metered it out because I can't find spec documentation for L-Jet AFMs.
- verified cold start injector not leaking.
- known good pressure pump - didn't have much of an effect.
- FPR vac test - unplugged vac line, system behaved as expected, pressure at idle rose by ~5psi
- known good 3bar FPR from an M30 - didn't have much of an effect. rail pressure stayed at 3bar as expected.
- plugged fuel tank return line and FPR exit. Turned ignition on to let pump charge, pressure jumped to ~100psi, dropped quickly to 1.5bar and stayed there. I opened the FPR exit and no fuel came out, so it was maintaining pressure.. not sure how to understand why the rail maintained pressure in this condition but not others.
- I timed the engine (with the distributor advance/retard lines disconnected and plugged) to ~18 degrees advance at 3k RPM, but didn't verify that the vacuum advance functioned. As far as I've been able to figure out, these distributors have a mechanical advance AND a vacuum advance. Is that right? What is a good way to test vacuum advance?
A new 2.5bar FPR and a few check valves are on their way to me to replace the missing and questionable units. If they do not cure the fuel problems, am I right in suspecting the injectors themselves? Can they be clogged *and* leaking? Can old fuel cause the power loss I'm seeing?
The symptoms:
- very down on power, minimal throttle response. I can barely get it above 70mph, and opening the throttle by hand in neutral makes it bog for a second before it spools up
- fuel rail loses pressure very fast. I put a gauge inline to the cold start injector - it goes down to 0 psi in several minutes, you can watch the needle drop.
Fuel pressure behaves kind of strange in addition to the rail purging - with the car idling it stays at the regulated 2.5bar with some vibration. When revved, it dips slightly, and drops by .5bar when the throttle is let go and the engine winds down off power.
What I've tried (mostly related to getting the fuel system to work right as a precursor to chasing the power loss down):
- replaced all small vac lines, inspected large ones
- verified AFM flap moves freely, but haven't metered it out because I can't find spec documentation for L-Jet AFMs.
- verified cold start injector not leaking.
- known good pressure pump - didn't have much of an effect.
- FPR vac test - unplugged vac line, system behaved as expected, pressure at idle rose by ~5psi
- known good 3bar FPR from an M30 - didn't have much of an effect. rail pressure stayed at 3bar as expected.
- plugged fuel tank return line and FPR exit. Turned ignition on to let pump charge, pressure jumped to ~100psi, dropped quickly to 1.5bar and stayed there. I opened the FPR exit and no fuel came out, so it was maintaining pressure.. not sure how to understand why the rail maintained pressure in this condition but not others.
- I timed the engine (with the distributor advance/retard lines disconnected and plugged) to ~18 degrees advance at 3k RPM, but didn't verify that the vacuum advance functioned. As far as I've been able to figure out, these distributors have a mechanical advance AND a vacuum advance. Is that right? What is a good way to test vacuum advance?
A new 2.5bar FPR and a few check valves are on their way to me to replace the missing and questionable units. If they do not cure the fuel problems, am I right in suspecting the injectors themselves? Can they be clogged *and* leaking? Can old fuel cause the power loss I'm seeing?
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