fuel pump issues
fuel pump issues
First off I'll tell you guys what my fuel system is. I'm running a TRE 255 lph in tank pump, factory in line pump, stock FPR and I have a new fuel filter. So about a month ago my car was blowing fuel pump fuses and it turned out to be a poor install of the 255 lph in tank pump. I didn't shrink wrap my 12 volt spade connection and it was shorting out on the sending unit. I shrink wrapped the connection and made sure it was not near any metal on the pump housing or the sending unit. After that all was good and I took the car to the dyno. Just recently my car started running really lean under boost over 3500 rpm. I had to increase my VE table values under boost by about 15 points to get AFR's close to where they were before. I figured the factory in line pump was shot and was creating a restriction to the 255 lph in tank pump, so I bypassed the factory in line pump and my AFR's got way worse. It hit 14:1 under boost at one point. So I went back to the garage and hooked up the factory in line pump and AFR's were good again. While dicking around with the pumps I would pull the fuse and run the car to eliminate line pressure. When I pulled the fuel pump fuse I noticed that the fuse was very hot......too hot to hold onto, yet no other fuses in the fuse box were hot. Have any of you guys noticed your fuel pump fuse getting excessively hot? Another thing I noticed was as soon as these lean AFR's started I could here the fuel pump humming while sitting in the car, but when everything was good I could not hear that TRE in tank pump. So I'm thinking that the TRE in tank pump is weak and I possibly did some damage to it when it was shorting out and blowing fuses. I wouldn't think that would damage it though, since fuses are there to protect components from shorts. I just wanted to run this by you guys to see what you thought of the situation.
As for the fuse, I have had the car not run because of the fuel pump fuse being loose one time. I put an o-ring on the fuse terminals so we'll see what that does for me. God I love these fuses from the 1930's......BMW should have got with the times a little earlier haha. I'm running 2 pumps because the car has 2 pumps from the factory and if I'm not mistaken almost everyone here runs both pumps even when they've upgraded the in tank to a 255 lph. I realize that one 255 lph pump should be plenty enough fuel, but there must be something up with my 255 lph. When I ran the 255 lph by itself the car was starving for fuel under boost.
Well I thought the in line pump was choking off the 255 lph, but when I ran the 255 lph by itself I ended up running leaner than I did with the 255 lph and the factory in line pump. I'm assuming enough juice is getting to the 255 lph pump since no one else has reported issues with the wiring for a 255 lph pump. The thing that's strange is that all was good and then one day my AFR's started going lean under boost. To me it seems like my 255 lph has gotten weak all of a sudden. I'm contemplating buying another 255 lph pump and running it by itself to see what happens.
I'm thinking of pulling the 255 lph in tank pump to see if I have something like this going on....... http://www.mye28.com/viewtopic.php?t=28 ... ht=255+lph
hmm very good to read that thread you found. almost sounds like what is slowly happening to my car, runs good but as the tank gets lower and lower i have lean surges like a mutha. cant go to the track half full. I really do need to upgrade my fuel pump as well. funny the stock stuff with a full tank of gas provides enough fuel at 15 psi of boost.
Well I pulled the TRE 255 lph in tank pump and there was nothing wrong from what I could see. For what it costs I'm just going to buy a new Walbro unit and see what that does for me. The TRE 255 lph couldn't supply enough fuel by itself and that's just not right. I think it must be on its way out, plus its louder than it used to be.