fuel pump and vibration

[Zigfried]

Hello. I have a 1997 318ti that is s/c by Downing/Atlanta. I have owned the car for a year now. I noticed a vibration coming from the rear end under a heavy acceleration. I thought it was going to be a center bearing. This week, my fuel pump went. I replaced it and now the vibration seems to be gone. Could there be a correlation? Could the fuel pump have been on its way out and contributing to the vibration in the rear? Anybody else have something similar? I figure that maybe the fuel pump wasnt supplying proper pressure. Could this have solved the problem? Thanks!

[cooljess76]

Sometimes if you listen carefully before you start the car, you can hear the fuel pump buzzing when you turn the key. It's louder if you remove the rear seat. As far as making the car shake or vibrate, well I never heard of that happening, but I wouldn't say it's impossible. I'd still do a thorough inspection underneath the car. Wouldn't want to find out the hard way that your differential, CV joints or driveshaft are bad.

[Zigfried]

Yeah. Weird. The vibration felt like it was coming from under my seat, towards the rear. I thought in the begining that it could have been a axle. I inspected them and they're fine. My subframe bushings are fine and I replaced the diff bushings a year ago. I thought maybe the center bearing could be the culprit because of where I felt the vibration. You felt it when shifting in to second while gettin' on it. It would hit so hard, the cd player would skip. Now it's gone because I changed my fuel pump. I was able to duplicate it all the time. I drive the car as not to make it happen. Sometimes. But now I can't make it happen. And I swear the acceleration has improved. Is it possible the supercharger was making the pump work harder and killed it slowly?

[cooljess76]

Originally Posted by Zigfried

Is it possible the supercharger was making the pump work harder and killed it slowly?

Absolutely. The factory FP is only designed to pump a certain amount of fuel per mintute. Downing Atlanta didn't offer a beefier fuel pump, instead they incorporated a rising rate fuel pressure regulator(RRFPR). I've recently heard someone mention running dual fuel pumps. If I'm not mistaken, this is a common mod on race steups and cars that suffer from fuel starvation. You'll probably be fine with your new fuel pump for many years to come. Figure if it lasted this long, it was probably going to fail sooner or later. Other members have had to replace their fuel pumps on normally aspirated engines.

[Zigfried]

Cool. I have 170k on it a that was the original pump from what I could tell when I replaced it. The car seems to be overall alot more "happy". Torque has improved as well. The vibration is gone and that is the best part. I think down the road, I'll look into a high perfomance FP.

[gene275]

had the same problem my shocks were bad in the rear and rubbing against wheel well i dont know what size rims u have but i put 17 's on mine so the height could have been an issue. i changed shocks and mounts no more vibration

[gene275]

but i never had a vibration from feul pump but anything is possible