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77 530i....fuel gauge needle either stays at empty or sometimes just swings to full on start up? There is actually about 2/3rds fuel in the tank. I've had the sending unit out and took a look inside and everything looks like it should. I've swapped out a few different fuel gauges that I had but no real change. I think there was a difference between the way the wiring was routed on the 76 models as compared to the 77 model which may be causing the issue? I have half a dozen fuel gauges but they are all slightly different and often the "flat copper wiring embedded in clear flimsy plastic" is bent or malformed or different than original. What's the best way to track down the fault? Karl

I'd look to the sending unit rather than the gauge. Ohm it out. IIRC it's supposed to be something like 0-82 depending on the fuel level. Take it out and make sure the float moves freely and watch the readings when you tilt it up and down, it should change.

You can't see resistance, so looking at the sending unit, other than to see if the float is going up and down, proves nothing. Break out the meter.