Fuel pump keeps running when car is off
 

Hey guys, I just picked up a 98 318ti, my first E36, and its been generally great. I do have an issue with the fuel pump though, it never turns off, I have to pull the fuse after I shut the car off or it will kill the battery overnight. Any ideas as to what would cause this? I searched and didn't find any info on this particular issue. Car is at 137k miles and well maintained with no other issues.

I have an update...I have a code for P0455 now, and the problem of the pump running continuously seems to be intermittent. I'm not sure the one that ran all night was the fuel pump. I looked at it again today and heard two different noises, the fuel pump I assume was much louder and had more whine to it. The other noise that ran all night was quieter but sounds like its coming from the fuel pump area as well. So, after putting the fuse back in to start it today, it acted like it didn't prime enough fuel and the engine sputtered and died after a low idle, if I used the throttle it would go up in rpm but it was shaky. I turned it off, then turned the key to on position with engine off and let the main fuel pump run for 30 seconds or so until it stopped, then turned it on and had no more sputtering issues, drove it to the store and back with no problems. After I got home I was able to turn the car off and heard the minor noise for about 5sec and then it seemed to go away completely. Weird situation for me.

Is the noise under the hood or in the back seat?

There is a normal whining noise under the hood when the car is on and continues for a bit after key is in off. I think it's something related to the brakes.

I've jumped my fuel pump to be always on in the past and can hear fuel splashing back into the tank when it was going. This is a back seat noise.


Did this just start happening or has it died overnight since you've owned it?



Not sure about that code. Something emissions related.

Possibly the pump relay is bad. Dirty contacts can fuse and/or have a poor connection. Relays in general can “chatter” or “buzz” depending on what’s happening.

Might be worth a look.

Hey there. The noise is definitely coming from the back seat area. For some strange reason earlier I was able to turn the car key on engine off a couple of times, the louder pump noise went for maybe 30 seconds before it turned off and the quieter pump area noise took over, but it actually turned off when I removed the key. It also stayed off after a 30min drive like normal. But then when I got home tonight the quiter noise was staying on after shutting the car off. I tried the key on engine off position again a few times but couldn't get the louder pump area noise, just the quiet one, which stayed on no matter what including when I took the key out, so I listened in the fusebox relay area and touched them all but they were all quiet. I pulled the fuel pump fuse so it doesn't kill the battery. Perhaps related? The fuel guage only goes up to halfway and stays there until fuel drops below that point. I put some B12 chemtool fuel cleaner in the tank today to see if that problem might go away.

Well...I've sort of solved the mystery...I didn't realize the fuel pump relay was covered by a plastic box, I pulled the cover off just now and it seems someone wired in a 20 amp fuse connecting two of the relay blades. I'm wondering if the relay went bad and this is how they decided to "fix" it?

Here are pics of the jumper that was installed. There is also a wire I circled that leads from the fuse block to the passenger side, but its very well done and hidden and I can't see what it connects to. I'm not sure what to make of this, but I removed the jumper and now the car seems to operate normally where the fuel pump only runs for a few seconds with key on engine off, and turns off when I shut off the car.

https://imgur.com/a/Vwb1Noi