czarredd

So my mechanic discovered that my fuel pump wasn't getting power and straight wired it to a relay under the hood that turns on with the ignition. The fuel gauge on my digital cluster isn't working and remains on full (all bars). We also noticed that my fuel sender is badly rusted and I need to replace it but I'm curious to know if the straight wiring could also be causing the fuel gauge to not work. Thanks

Cliff Harris

The fuel pump and fuel level sender are completely separate (but do share the same ground).

The fuel pump relay should come on for 2 seconds when the ignition is turned on and then shut off. It turns on when the engine is turning (cranking or running), so there is not 12 volts on the fuel pump all the time. If you check it when the engine is not turning you will see no voltage.

czarredd

Thanks Cliff, so could the straight wiring of the fuel pump cause my digital gauge not to read my fuel levels? Wasn't sure if there is a special wire at the fuel pump to communicate with the cluster for fuel that's being bypassed. Thanks for all your help.

Cliff Harris

The fuel level sender gets 5 volts from the dash and sends back a proportional voltage for the fuel level. Completely separate from the 12 volts (or so) that goes to the fuel pump. It has no way to measure bypassed fuel.

czarredd

Thanks!

czarredd

So, I don't have my fuel sending unit out of the car but I'm seeing pics of one and it appears that there are 2 sets of wiring harnesses on it. Does one harness supply power and the other communicate with my digital cluster's fuel gauge? My thought is that maybe my power wiring and fuel gauge wiring may be faulty therefore causing my fuel gauge not to work on my digital cluster. Any thoughts? Thanks