Expert: Josh Fields - 9/20/2006

Question
Hello Josh,
I have a 91 BMW 318is.  I have had the fuel pump replaced 3 times in a week but it keeps going out.  The filter has also been changed.  Any idea what the problem could be?  It is not the relay as with the 2nd and 3rd pump it still runs, just cant get any gas to it once it hits 2000rpm.  So I can only go 10mph.  If the car sits and cools for a few hours it drives somewhat normal for 10 miles or so then same issue.  After it sat 4 hrs I drove it home and everytime it hesitated, I hear a high squeeking sound from the back of the car.  (Im assuming the fuel pump.)  It would hesitate for 3 seconds, then stop making the noise and continue fine.  Any thoughts at all?  Please help, I dont want to get rid of it, It only has 81000 miles on it.

Answer
Clayton,
 For some reason I've had a rash of 318 questions lately, all relating to lack of fuel.  Now you mentioned 2nd and 3rd pump.  This is confusing to me, as I was only aware of 2 pumps on these cars.  If your car has 3 pumps, that might be the problem.  You should only have 1 in-tank pump, and one external pump, which is right in front of the rear tire.

 If the external pump is failing (pretty common) it makes a whizzing or a whining sound.  This will cause the in-tank pump to absorb the load, and will cause it to overheat and fail (been there, done that).

 So I would unplug the intank pump (beneath rear seat) so it will not pump.  Then have someone turn on the key and go down by the driver's side (US cars) rear wheel and listen for the pump to work.  If you dont hear anything, place your hand on the pump and feel for vibration.  If you feel the pump vibrating... it's working, if not... then obviously its bad.  This could also be blocking the in-tank pump from working as well.

 That being said, you may not have the external pump, I think some of the later model vehicles were only equipped with in-tank pumps, like most other vehicles.  If this is the case, then you have to figure out why your in-tank pump is failing.

 Good luck,
 Josh