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Sending Unit, Fuel for International 674 Tractors

P

Paul in WI

Member
My fuel gage always shows full. If I take the wire off of the sending unit and ground it to the frame the gage will drop to empty.
I removed the sending unit and moved the floot by hand and I was able to get a LITTLE movement on the gage.
I would say the gage is good.
What is the best test for the sending unit to tell if it is bad or not?
 
(quoted from post at 12:14:52 03/27/20) My fuel gage always shows full. If I take the wire off of the sending unit and ground it to the frame the gage will drop to empty.
I removed the sending unit and moved the floot by hand and I was able to get a LITTLE movement on the gage.
I would say the gage is good.
What is the best test for the sending unit to tell if it is bad or not?
Click to expand...

"What is the best test for the sending unit to tell if it is bad or not"

I think you already have determined it's "bad".

The factory shop manual typically will give the resistance in Ohms when the float is at the "empty" position and the "full" position.

Without that info, it's impossible to know if it is "out of spec." or not.

To give you an idea of the variety of systems used, here's a chart of some automotive setups, tractor guages vary in a similar manner.

8EDOqQs.jpg
 
Hi Paul, most times the problem is electrical, bad ground or bad contacts in a connector. Since you are in WI, USA your 674 is probably a USA crate unit with Delco wiring.
Here in Canada our Doncaster built IH tractors were shipped directly to Canada and had Lucas electrics which were subpar to Delco.
The Lucas version had an electrical connection behind the seat under the deck that supplied all the power to everything on the rear of the tractor.
The other thing there was one ground wire that supplied the ground for the rear of the tractor and it was connected to one of the rear bolts that hold the deck under the seat and a poor ground caused all sorts of funnies.
 
An OHM meter and watch for the needle to move as you move the float. The gauge usually will go from full to empty or vice versa with the live wire shorted to ground. If the float does not move the needle the sender is shot and could try a generic in there as long as you can get it to orient right to move freely. I used a generic one in my 806. Dad asked which way I wanted it to read. I said so it is correct on the empty side. Full will not matter.
 
First, thank you to all that answered me!
I pulled the sending unit out of the fuel tank and with my Fluke meter the unit read .6 when empty and 60 ohms when set to full.
When the wire going to the gage is remved the gage drops to empty. With the sending unit out and the wire conected to it and the sending unit grounded to the (frame) I can get the gage to move a about 1/2 scale but read the wrong direction.
I put the sending unit back into the tank and bolted it in place. the gage read emty , as soon as I connected the wire the gage went to full.
I think my problem is that I have a short in the wire from the sending unit to the gage.
What do you all think?
 
It's probably the sender unit, or, the float could be rubbing/hanging up on the inside of the tank. Unhook both wires, touch them together, and see if the gauge moves. If no movement, see if the ground wires are hooked up to the RR seat mount stud. Also there is a plug in the harness under the seat platform. Check that it is making good contact when plugged together. Remove the sender, use your meter and move the float arm SLOWLY thru its range of motion. If it fluctuates or drops off scale during the movement, it is bad. All that said, it is safer to just look into the tank, because I really doubt you would ever get the gauge to be very accurate. Also those tractors pick up fuel from the right side of the tank and return to the left. If you operate sideways on a hillside long enough with the tank lower on the left, and you have 1/4 of a tank, it will run out of fuel, unless you turn around quick enough and get the right side lower, so fuel can run over there. I usually keep above 1/2 all the time, to be safe, on everything I own. Mark.
 
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