Fuel Gauge Issue on 95 G50

[piranhamatt]

The problem: The fuel gauge in my 95 Q reads full almost all the time. Sometimes, just after stopping from driving, it will drop to between 3/4 and 1/2. When this happens, it will go back up to full once I start driving.

The car:
95 Q45 with a 5 speed swap. Unfortunately, I don't know if the gauge stopped working when I did the transmission swap, or a few days later when I installed a Dakota Digital speedometer calibration box.

What I've tried:
Uninstalling Dakota digital box (just in case).
Replaced fuel pump and entire fuel sending unit assembly.

Next on my list:
Install replacement cluster.

I'm just curious, does anyone else has thoughts on what may be wrong? My fear is that somehow the wiring from the bundles that went to the auto trans / shifter had something to do with the gauge signal.

Just for kicks, here's a picture:

[Infinitiguy19]

My guess would be that the fuel gauge in the instrument cluster is toast.

Did you cut the wiring or secure it to something and leave unconnected?

[piranhamatt]

Agreed. I'll be picking up a replacement cluster soon. All the wires from the shifter area were disconnected and capped, nothing actually cut. Thanks for the input.

[Skibane]

Assuming your G50 uses the same basic fuel gauge scheme as my Y33...

The fuel gauge sender is a variable resistor, with the resistance getting higher as the fuel tank gets more empty. With a full tank, it's 4-6 ohms - With an empty tank, it's 80-83 ohms.

So, if the connection from the tank sender to the gauge was broken (open), the gauge would measure a very high resistance, and would show the tank as being empty.

If the connection from the tank sender to the gauge was shorted to ground, the gauge would measure a very low resistance, and would show the tank as being full - which is what you're experiencing.

So - Assuming the gauge is OK, it sounds more like the fuel sender wire is shorted to the chassis (pinched somewhere, maybe?) than a poor connection (which would increase the measured resistance, rather than decrease it).

[piranhamatt]

I hate when I see threads that have no resolution, so here's what happened:

I must have shorted wires at some point while finishing my 5 speed swap, as the wiring on the circuit film on the back of the cluster was toasted.

A replacement cluster fixed my issues, and smoothed out my speedometer.

[Q451990]

Thanks for the update!