Hi everyone,

Have a 1988 740 turbo wagon, lh 2.2, b230ft, with over 240,000 miles on the car.

Having some problems with a noisy in line fuel pump. Sometimes it's not to loud other times it's pretty bad. Pretty sure I can hear it humming while idling sitting in the car. Listening from under the car it has like a scratchy kind of sound, maybe almost like a bad bearing or something.

I can hear the in tank pump humming from the filler and don't have any symptoms when below a 1/4 tank. I will be pulling the sending unit this weekend to check anyway.

Other things to note: I have maintenance records from the PO with a fuel pump change at around 200,000 miles (not sure if it's Bosch or not).

My hope is that I have a bad in line filter. I changed it when I got the car but the car sat for 3 years prior to 8 months ago.

Could a bad/clogged in line filter be causing my pump noise?

Have been dealing with the noise until Todat after a 150 mile round trip today the car would start to buck/stutter under light boost. Took it for a drive 10 minutes after parking and it was fine again, still loud though.

Sorry for the long post and welcome any input .

Thank you much

Hi everyone,

Fixed the issue, I'm pretty sure at least. Turned out to be a dead in tank fuel pump.

Yesterday determined the wiring was in good order to the sender. Applied power to the pump from the battery and nothing (tried using fuse 1 (in line pump) and fuse 11 (in tank pump) but am unsure if I did it correctly).

Got a "new" sending unit and in tank pump from the junkyard and all seems well. My sending unit was in dire straits.

I still hear the main, in line, pump but not as bad so far.

One note is that even with a dead in tank, listening at the fuel filler still produced noise that I thought was the in tank pump working. Think I was just hearing air as now I can hear the pump "whirring".

Thanks for the help I much appreciate it

art's links are great. just make sure the inline pump is a bosch. the others do not have enough volume to run right. good luck, chuck.

http://forums.turbobricks.com/showpost.php?p=5582094&postcount=26
--
Art Benstein near Baltimore

http://cleanflametrap.com/transferPump.htm

Update:

So I tried to do as art suggested...

Maybe I did this wrong, correct me if I did please.

1) I hooked up a clear line from the sending unit output and ran it into the gas filler.
2) Pulled the fuel pump relay and jumped 87/2 to 30.
3) Pulled fuse #1 (for the fuel pump, ect, engine control). Kept fuse #11 in (in tank pump/o2 sensor fuse)
4) put the key to position II

Nothing. No fuel coming out of the clear line into the gas filler.

Did I do the procedure incorrectly?

I'm going to do some more research but it seems like my in tank pump is dead or not getting power/ground. Any suggestions on how to test?

Thanks as always

Maybe I did do it wrong...

From brickboard faq: "To run or test the In-Tank Pump, remove fuse 1 and in-tank pump fuse 11 and apply battery voltage from the fuse 1 terminal closest to you to the Fuse 11 terminal that is farthest away from you, i.e., toward the engine"

Is this saying make a jumper from one slot in fuse 1 socket to one slot in fuse 11 socket and turn the key to position II?

Thanks again and sorry for the trouble

Hi and thank you,

I actually have that pulled up to test this weekend :)

If I didn't want to get into the sending unit area will unhooking the fuel line to the in line pump work as well for this test?

I plan on getting into the sending unit anyway but just wanted to know for future reference.

Thank you much

Yes, testing at the input to the main pump would accomplish the same thing. In addition, it would preclude the imagined blockage of that sender-to-main pump hose (imagining the inner lining could become detached and block it) so yes, even better. Maybe a short hunk of 1/2" copper pipe/tube would join the hoses.

I can't tell you exactly how to run the pumps manually in a 700, with its ashtray fusebox, but perhaps a jumper or paper clip bridging the fuel relay terminals 30 and 87/2. And check the 700/900 FAQs as there may be some help on this.
--
Art Benstein near Baltimore

98% OF AMERICANS SAY 'OH S***' BEFORE GOING IN THE DITCH ON A SLIPPERY ROAD.
THE OTHER 2% ARE FROM MAINE, NEW HAMPSHIRE & VERMONT, AND THEY SAY, 'HOLD MY BEER AND WATCH THIS.'