[slo_335-e90]

Hey everyone,

So I'm having some trouble diagnosing an issue with my car. Last week I installed a walbro LPFP through my local shop, and it has been running fine. Ran it through a few tanks of gas without any issues, and ran it under a quarter of a tank without issue (cycled 2 tanks of gas). However, after filling it up a 3rd time, once I hit about a quarter of a tank the car would start misfiring once I hit about 2-2500 RPMS. I wouldnt throw check engine lights immediately, and when I did the code reader showed something about the HPFP. I went to bring it to BMW this morning, and before I got there I put some gas in getting it to about 1/2 a tank. Once I got it to half a tank I couldn't get it to misfire again. BMW didn't find an issue and said if it happened again to bring it back. Well tonight it hit just about 1/4 of a tank and it started happening again. Thinking it was relevant to the fuel level, I went to the nearest station and filled up. Problem went away again. At this point I have no idea what it could be. Is it the LPFP? or the HPFP? or neither? Any help would be awesome!

[M3_Dylan]

Sure sounds like walbro is to blame here.... Under a quarter of a tank your LPFP is now using the syphon to gather fuel and fill the bucket.. Above that the fuel level is so high fuel pours over the edges of the tank and submersible the pump in fuel. If I were you I would log LPFP pressure at a full tank and at a quarter of a tank. Should be 72psi if what I'm thinking is right the hose attached to your syphon is lose and is causes you to loss pressure and not suck up enough fuel under WOT.

I could be completely wrong but it worth a shot

[slo_335-e90]

Originally Posted by Dylan335i

Sure sounds like walbro is to blame here.... Under a quarter of a tank your LPFP is now using the syphon to gather fuel and fill the bucket.. Above that the fuel level is so high fuel pours over the edges of the tank and submersible the pump in fuel. If I were you I would log LPFP pressure at a full tank and at a quarter of a tank. Should be 72psi if what I'm thinking is right the hose attached to your syphon is lose and is causes you to loss pressure and not suck up enough fuel under WOT.

I could be completely wrong but it worth a shot

Yeah thats what I was thinking. Ah ok I'll have to call the place that did it and see if they can check it out. Thanks for the tip!