Whine/Hiss from rear of car? Fuel pump? Video inside.

[davesmystery]

Edit: This was on my 1992 325ic

This video was taken on the passenger side ahead of the rear wheel. I've read a lot about fuel pump whine but haven't found a good video of what it actually sounds like. It's louder outside under the car, but can be heard inside the cabin as well. If it's not the fuel pump, I can only think that it might be a hole in the exhaust somewhere.

It's been doing this since I bought it about a month ago. The PO says the fuel pump was replaced, he's been verifiably honest about everything else he said was done so I see no need to doubt him here. But I have read that if parts of the system are clogged with gunk it will quickly kill a new pump. I suspect if this is the case that the PO's mechanic probably just swapped in a new one, heard it go away and figure it was fixed.

The car drives fine, idles well, doesn't cut out, etc. I did have a leak at the FPR o-ring but I just replaced it and it leaks no more. I can't find any other leaks and although the fuel lines are a bit dry, they aren't leaking that I can see.

Just want to get some advice as to what this might be and what can/should be done about it. Thanks!

[jeffnhiscars]

I'm not sure what fuel pump setup you have but we had a very loud sucking noise coming from that area when the intake pump was out.This left the pusher pump by the fuel filter to suck which is was not designed to do so it made a lot of noise

[davesmystery]

Where is the intake pump (or at least, how does RealOEM term it)?

And by the pusher pump, do you mean part #9 above the fuel filter?



http://www.realoem.com/bmw/showparts...81&hg=16&fg=15

[jeffnhiscars]

Yes, #9 is the pusher pump and while its hard tell from your video, if that pump is doing its job as well as that of a non working in tank pump it will def make a loud sucking noise. I don't recall if the pumps share a fuse or relay but you want to deactivate the in tank pump to se if that makes a difference. If you do wind up having to disconnect it at the tank be sure to disconnect your battery first. I suspect one of the pumps is bad

[davesmystery]

Well now I'm a bit confused because I've read that the later models only had one in tank fuel pump. I suppose what I'm going to do is drain the tank, pull the in tank pump and see what the inside of the tank looks like and replace the fuel filter since I don't know when the last time that was done. I've also ran some injector cleaner through the system, so I'm wondering if that might have some sort of impact on it.

[DaveSmed]

It's a 92, they only have the single in tank pump.

How much fuel was in the tank? It's loud, but sometimes aftermarket pumps are that way.

[davesmystery]

Thanks for confirming. It's the same regardless of how much fuel, from empty to full.

It's interesting you mention that because nearly everything that the PO seems to have replaced on the car has been aftermarket local auto parts store stuff. I'll be sure to check what kind of pump it is when I pull it out, if it's dodgy I'll replace it with something of better quality.

[davesmystery]

Update, I took the backseat off and the fuel pump cover off, then started it with the doors closed and it's definitely the fuel pump making the noise. Don't know why I didn't think of doing that before.

Plan is still to drain the tank, check the pump and tank and replace the fuel filter.

[jeffnhiscars]

Those are good steps but I would do them in the reverse of the order you listed them. When the pump is out you can do a visual on the inside of the tank to see if theres a reason to drain and remove it. Obviously a plugged filter or intake screen will point to the tank anyway but its a nasty job worth avoiding if possible