Why does my car have an extra fuel pump?

[performedbeef]

2/1988 325i cabrio. Shows lots of signs of abuse. The car runs okay, idle surges when cold, could use a valve adjustment. No trouble with fuel delivery while driving though. Constantly indicates empty tank.

It looks like the PO had some problems with the fuel pump and "fixed" it in an unusual way. This extra pump is stuffed in with the expected one. The red wire is spliced in to accessory power in the driver's footwell and the pump comes on after turning the key to the first position. It makes a very loud whine. I've done some reading into fuel delivery in Bentley manual but I've got no idea where to start with this. What could have been wrong with the original pump that called for this replacement? How can I go about testing the pump that's still in the tank and determine whether I can repair by putting everything back the way it was with a working pump?

[roznic]

do you have one under the car with fuel filter, pass side?

[mpowerful]

The main in tank pump is currently not connected. Unless they hacked the connector for it to power the new pump you could pull off the newer pump, pull out the old in tank pump, connect it to its proper plug and see if it comes on when you crank the car. If not check for power to the original pump connector. If power then most likely the in tank pump has crapped out. I put an e36 6cyl pump in place of my orginal pump because i got it for like 4 dollars. Going on 10000 miles no problems.

[jlevie]

Pull that junk out, undo the wiring kludge, and replace the in-tank pump with a new OE/OEM pump.

[mpowerful]

Jlevie, your advice is always sound, but I do have to dissent here. The OE or OEM pump is very expensive. Aftermarket would be much cheaper and just as reliable. I would however do it right and put it back into the tank with the in tank carrier. That crap they have on there is just dumb.

[TobyB]

That is... really quite special.

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