I have a 1979 F150, 460, dual gas tanks.
The rear gas tank quit working about 15 years ago and have been using the front tank.
Truck has sat for 3+ years and I'm bringing it back to life.
I drove the truck about 11 miles and then no gas out of front tank.
Pretty sure front tank is full of rust and clogged.

Purchased a new rear tank and sending unit. Removed old tank and wanted to test the sending unit to see if gas gauge would work.
Hooked up sending unit and moved float to full position hoping gas gauge would move but nothing happened. It does move if switched to front tank.

Can I just plug the sender unit in and see results?

 

So long as both terminals (signal and ground) are connected to the heart-shaped connector coming from the truck, the sending unit should work regardless of whether it is physically mounted in the tank. Try these steps:

1) Make sure you have power at the sending unit. Connect a test light to the wire coming from the TRUCK that goes to the YELLOW wire on the signal unit. The test light should BLINK once per second.

2) Check the resistance of the sending unit (10 ohms full, 70 ohms empty).

3) If all else checks out, you probably just need to sand down the ground on the crossmember.

 

Thanks for the info.

I already see an issue. I was putting the float in the empty position thinking it was in the full position. Used an ohm meter and did get the readings you posted. Will try again tomorrow with the float in the proper position.

Thanks
James