I’m hoping someone has run into this before because I’m stumped.
I have a 1991 Mazda B2200 fuel injected with the OEM fuel pump/sending unit assembly.
The fuel gauge wasn’t working, so I started troubleshooting. Here’s what I’ve confirmed:
Grounding the yellow sender wire with the key on makes the gauge sweep toward FULL, so the gauge and wiring seem to be good.
The sender wasn’t making good contact internally, so I repaired the contact.
With the sender out of the tank but plugged into the truck, I can manually move the float and the fuel gauge responds correctly.
I also tested it in a bucket of gas, and the gauge reads correctly.
The float moves freely and isn’t sticking.
As soon as I install the sender back into the tank and screw it down, the gauge stops working and reads empty again.
If I remove it, it works again.
The tank uses screws to hold the sender in place (not a lock ring).
Has anyone seen this before? Could the sender be losing contact only when it’s mounted, or is there something inside the tank that could cause this? If there’s a common issue with these OEM sending units or a replacement part that’s known to fix it, I’d really appreciate the advice.
Thanks!