How to Test a 1940 Ford gas sending unit
 

I have a fuel sending unit that came with a very nice used tank.
I used the tank and installed my sending unit, as I knew it worked.

I would like to Test this left over sending unit ( 01A-9275-A ) to
see if it works before offering it up for sale here.

Is there a way to Test it using an OHM meter, as I don't have a
gauge to hook up, to test it with ? Thanks for any help.

Re: How to Test a 1940 Ford gas sending unit
 

There is really no ohms value that would tell you much, it doesn't work on resistance. It will most likely depend on the condition of the points inside the sender. The ohms readings should be very low with the points closed and zero with the points open. The one I measured inside the unit read 2-3 ohms on the heater coil and 8-9 ohms on the calibration resistor.

Re: How to Test a 1940 Ford gas sending unit
 

JSeery, can you test the unit by connecting the sending wire to the test unit, a ground wire to the case of the test unit, and move the float through the range of motion? Mine reads 7/8 full on the gauge with the float all the way up and empty at all the way down. I tried one of the repos and fell victim to their worthlessness. Reinstalling the OEM sending unit with a new float is a spring project.

Re: How to Test a 1940 Ford gas sending unit
 

Yep, should be the same arrangement as it would be the sender in the tank. The sender is providing a ground path for the gauge and the heater coil opens and closes the points to pulse the current flow. Raising and lowering the arm changes the pressure on the points which varies the pulse rate. The gauge has it's own heater coil and the current flow in the gauge is the same as the sending unit. So if you have a known good gauge that would be the best way to test a sending unit.

Re: How to Test a 1940 Ford gas sending unit
 

Why not just disconnect the wire on the one in your car and connect it to the unit in question then ground it via a jumper wire with alligator clips on each end them move the arm up and down and watch the dash gauge for movement.

Re: How to Test a 1940 Ford gas sending unit
 

When you do this remember to give the gauge a little time to respond...it will not be instantaneous.

Re: How to Test a 1940 Ford gas sending unit
 

Do this:

Lay a piece of cardboard or blanket on your trnk floor. The rubber trunk mat is also good.

Lay the sending unit on the blanket and attach the wire from the gauge to the little screw on top of the sending unit using alligator clipped wire.
Using another wire with alligator clips, attach one clip to one of the screw holes on the sender and attach the other end of the wire to car ground, like the trunk latch on the floor. Then, flip the ignition switch to "ON" and move the float up slowly and then slowly down to see if the dash gauge shows a reading. Don't let any of the wires touch each other. If gauge doesn't register a reading shut of ignition switch, disconnect sending unit and carefully pry off the top. Then clean the internal points with 600 grit emery paper. Reassemble and try again.