fuel gauge PLEASE HELP!!!

[Slick92GS-R]

i have this same problem ....i fill the tank (13+gallons)..needle shows full, my odo/trip doesn't work, so i don't know how many miles driven but when needle gets to half.. fuel light comes on.. i've figured the light is correct & the gauge is wrong ..

1. while at an HPDE w fuel light was on, i got bad hesitation on a long right hander. (late in the day after 3 sessions)
2. i was at an auto cross fuel light on.. hesitation on quick right left combo (last run of the day)
3. i ran the fuck out of gas one day, light blazing, half tank showing

i have 87 325e that i've swapped in a 325is cluster.. my old original cluster has Si batteries woes..

[e30power7931]

ok thanks guys

[Jean]

Then you might have a wrong cluster or coding plug in your car. I would check with another member who has the same model/year car as you that...

[e30power7931]

i have only one sender. Everytime i replaced gauges or sending units when i would be on emtpy my fuel gauge would be reading half a tank. each thing ive tried has had the same results

[thereisnoyun]

did you replace both sending unit? the one next to the pump and the one on the other side?

[Jean]

yeah we have done all these test but nothing has worked....im thinkin just say f it and give up lol

What do you mean nothing worked...what were the results? Depending on the results you can deduct what the problem may be.

[e30power7931]

yeah we have done all these test but nothing has worked....im thinkin just say f it and give up lol

[Jean]

According to realoem your car has one fuel level sender, correct? http://www.realoem.com/bmw/showparts...46&hg=16&fg=05

You can do the following test:

a) disconnect the wiring from the sender unit, one of the 3 wires activates the dummy light, and another is for the gauge, 3rd is ground. when you short one, the light comes on. test it.

b) remove the sender and place it in a bottle of water or any other liquid while moving it up and down to simulate the amount of gas in the tank. measure the resistance with a DMM

c) replace the sender with a variable resistor and see how the gauge behaves, does it sweep the full empty-to-full rotation? you'll need to look up what resistance your gauge needs.

I've done this on my early car, IIRC the range was 4ohms to 70-80ohms for the sender.

[accident]

Ecu?

[e30power7931]

i have replaced the cluster 3 times 2 times with 87 model clusters and my current one is from an early 88 cuz the tach went bad....in all of them the gauge never worked and i put in the correct sender all 5 times i have tried.....im thinkin about givin up and sayin ive done all i can all we can do now is hope lol

[accident]

Jean, would the gas light turn on at 1/2 tank with a late cluster in an early car? From what he's saying it seems like the needle itself is working fine, but the light is wonky.

[Jean]

Do you have correct cluster or sender in your car? this happens if you have a late cluster in an early car. Fuel gauge will not read correctly.

The "Empty fuel" light indicator is triggered when the float in the sender is clost to the bottom, so it's almost an ON/OFF switch where the sender/gauge are dependent on each other to give you correct reading.

[accident]

have you tried replacing the whole cluster? the SI Board or the rest of the electronics could be bad.

[e30power7931]

yeah

[accident]

that is what my gauge is displaying

So when the gauge gets to 1/2 the gas light comes on?