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Old 06-12-2019, 06:26 AM   #1
Aufbau Principle
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Join Date: Jan 2013
Location: Massachusetts
Posts: 114
Gas gauge weirdness

1984 325e, single fuel level sender.

Gas gauge has been stuck on full for some time, very rarely worked. Put in a late model cluster when I did a motronic 1.3 conversion, swapped the old gauge over to keep it with the fuel tank, same problem. Put a different fuel level sender in yesterday, still stays on full.
I checked the resistances of both senders and they both read 0 ohms at empty and ~74 ohms at full when physically tilting them, so the sender seems to work.
The gauge goes to empty when the sender is unplugged from the harness, and I can simulate a full tank by jumping pins 1 and 2 from the harness, and also make the low fuel light come on by jumping pins 1 and 3, so the gauge seems to work. However, plugging the sender into the harness makes the gauge read full, which means that the plug is somehow shorting itself out?
My OBC range function also seems to be stuck reading 31 miles after messing with the senders, when it would previously display other numbers. The low fuel light also seems to have stopped working if I plug in a sender outside the tank, though I'm not sure about that one.
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Old 06-12-2019, 02:22 PM   #2
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I recommend you repeat your fuel tank resistance testing but at the cluster harness. You may find a break in the wiring from the fuel sending unit to the cluster.
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