Fuel guage problem

[ChimpWithWrench]

I have a 77 c10 454 that I just installed a sniper on. Prior to the sniper install the guage worked. While swapping the sniper in I modified and installed an r10 fuel pickup and sending unit cause I wanted to use an in tank pump. It has 4 wires. 1 pump power, 1 sending unit power, 1 ground for pump and 1 for sending unit ground. I checked the grounds, sanded down to bare metal on frame and hooked both grounds together. Fuel pump works but the guage is pinned over full with the key on and 3/4 with the key off. I pulled the power to the sending unit with no change, and also pulled the ground also with no change. Only thing I can think is that the power for sender is grounded somewhere or the r10 sending unit is different somehow. I did test the sending unit prior to install and got 0 ohm down and 90 ohm up. Really just looking for someone who knows the r10 to tell me it's the same and to keep looking for the short.

I'm only running 1 tank and the switch is on the correct tank.

 

[Ricko1966]

If you ground a power wire,you blow a fuse,melt a wire or start a fire. I would assume your gauge has power from a keyed source through the gauge from to the sender which varies the ground,to indicate fuel level. Are you using your original sender wire to the gauge? If so connected to ground vs. disconnected should show full and empty. If that passes check the resistance values of your old sender and compare .

 

[ChimpWithWrench]

Thanks Ricko I am using the orginal guage and sending wire. I did figure it out. When I shortened the return tube and reattached with a rubber line I didn't take into account I would be severing the ground between the sender and the top of the unit. Added a ground wire and all good now.