1998 E39 528i auto fuel gauge problem

[Solo Man]

My old 528i suddenly developed a problem with the fuel gauge. My brother was filling up just before the price hike and left the car idling. When the tank was full the gauge still sat on quarter full as before filling. He drove about 80km with the gauge slowly going down until the reserve light came on and the needle hit the empty mark. There must still be about 60l petrol in the car but the gauge shows empty and the orange light is on. Have disconnected the battery overnight but still the same. Any suggestions as to what could be the problem?

 

[Ralf*]

sounds like the fuel sender unit is faulty ?

 

[A.C.SCHNITZER]

sounds like the fuel sender unit is faulty ?

A+++++

 

[Solo Man]

Is the sender unit located under the rear seat under the carpet?

 

[Ralf*]

Is the sender unit located under the rear seat under the carpet?

not sure about the E39, I haven't as yet removed my rear seats to look, but on my E38, removed the rear seat, and under the seat is the fuel tank, .....(if I am not mistaken), on my E38 the sender was in the rear left hand side.

you might also before dismantling the sender unit, just trace the wires to check that there isn't somewhere a break or a short to the car body earth.

 

[Clownshoe]

Two fuel senders. They are located under the back seat. Usually only one will be faulty.

To test get a multi-meter set on resistance. With the rear seat out, no need to remove the senders, just remove the plug attach the multimeter and if you have resistance and a circuit it should be OK. To check rock the car while the meter is attached you should have a restsance change as the fuel sloshes in the tank. If OK check the other one. If both OK you should just take them out to make sure that they haven't got stuck or something.

Left side and right side are different, right side has the fuel pump attached to it. DO NOT let bmw try and sell you a fuel pump aswell. They tried that with me.

New sender is about R1200

 

[Solo Man]

Thanks for al the replies guys! Have forwarded it to my brother to see if he can find the problem as the car is with him in Upington. He is quite clued up on mechanical/electrical stuff, so he should be able to sort it out. Thanks again.

 

[Clownshoe]

P.S> remove the back seat by yanking up on the front of the seat. It is held in by two clips.