740 Fuel guage erratic

dannyboy · Post by **dannyboy** » 27 Sep 2006, 04:53

My wife's 740, 2,3, EK, 1988 has just gone over 400.000 Kms without any major problem (so far) except that, like many of them, she has lost its interior ceiling cover (no, not my wife).
However, for a few weeks now the fuel guage has been giving erratic readings (it changes all the time even if the tank is full) so that we can not rely on it any more and we must make sure to reset the odometer when filling up the tank.
Has any of you experienced that problem and found how to cure it?
Is there a relay or anything that could be checked without dismantling the gas tank?

Thanks to you all beforehand

LaRy · Post by **LaRy** » 27 Sep 2006, 09:45

It could be bad grounding of the fuel level sensor because of rust. I have met that problem. Normally it should be a ground connection wire from the fule tank to the car chassi because the tank is made from plastic. If you take out the carpet in the trunk you will find a square cover in upper left corner. Remove it, and under there, you will find all connctions to the fuel tank. Messaure the resistance from the metallic top of the fule tank to the chassi, should be zero. If it is not zero that is the problem, make a new connection from the tank to the chassi. Connect the wire to the tank by a small hose clamp. Put the clamp around one of the smaller tubes for the petrol hoses.Clean from rust at connection point.
If you don't have an ohm-meter, just press a grounded cable to a not rusted clean spot of the tank and see if it helps.

dannyboy · Post by **dannyboy** » 28 Sep 2006, 01:37

Many thanks for your advice.

I'll certainly try that.

Thanks again