Testing the Fuel Gauge

[kittenb]

Hi all, I need help
I have a 76 Scout II. I bought it at the first of the year and the fuel gauge has never worked. Before going thru dropping the tank and testing the sender I was wondering if there was a way to test the fuel gauge itself. I have grown tired of knocking on the tank to listen for an echo.

Thanks!

[Eric VanBuren]

The biggest cause of failure of the fuel gauge to work is the cheap stamped steel nuts connecting the gauge to the circuit board.

Disconnect the battery and pull the fuel/amp cluster from the dash, don't disconnect the plug just pull it out far enough to tighten the nuts, you will usually find them finger tight. Re-attach to the dash and see if it works.

If that doesn't fix it the best way to test is to go to your local Radio Shack and get a pack of 10 and 33 ohm resistors.

There is a disconnect at the rt rear of the truck for the wire leading to the sender. Disconnect that and connect a 10 ohm resistor to the harness side wire and a good clean ground. With that connected the gauge should read at the "F" +/- a needle width. Connect a 33 and 4 10 ohm resistors in series and connect those to the wire and ground that should make the gauge read "E" +/- a needle width. That will test the gauge and all the wiring.

If it fails the test there, you can test at the back of the gauge. The terminal on the rt side of the gauge is the one that goes to the sender. You need to be very careful testing there, because the wires that connect to the ammeter are always hot if the battery is connected.

While you are in there I recommend replacing the stamped steel nuts with brass ones. It is one of the first things I do when I get another IH. They are 10-32. I never disconnect the plug from the circuit board as the pins on the circuit board are somewhat fragile and can come out of the board when you disconnect the plug. Those pins being loose can also be a cause of the gauge not working.

[kittenb]

Thanks! We did take the plug out last night before I posted I did see one was loose.

[scoutboy74]

It's o.k. Sometimes you need to D/C the plug for better access to the gauge guts. You just need to be very careful and sometimes even then you can loosen one or more of the pins. This was just a poor design, but hey...it's late 60's tech at it's best. You can bolster the stability of the pins with some solder around the base of each loose pin. Just make sure that the solder you apply around a pin does not create a bridge contact between any other pins.

[kittenb]

Originally Posted by scoutboy74

It's o.k. Sometimes you need to D/C the plug for better access to the gauge guts. You just need to be very careful and sometimes even then you can loosen one or more of the pins. This was just a poor design, but hey...it's late 60's tech at it's best. You can bolster the stability of the pins with some solder around the base of each loose pin. Just make sure that the solder you apply around a pin does not create a bridge contact between any other pins.

Ok thanks. We were going to try to solder the loose one and see if that was the cause. Another thing I noticed. When we unpligged the gauge, the plug didnt have metal rings in all the holes that it plugged into. Would this make it lose contact & not work ?

[kittenb]

I forgot to mention that we just had to clean up the amp gauge due to no power. Boy does she start like a dram now

[Eric VanBuren]

On the Fuel/Amp gauge there aren't that many circuits that are actually used so no not every position in the connector will have pins and wires. You'll also notice that there is one female pin w/o a wire, this is to index it so you can only plug it in one way.

If a pin is damaged soldering is a good idea but that can be difficult some times. The other option for some of the connections is to use a ring terminal under the stud and splice that to it's respective wire, by-passing the pins and connector. It is also important to note to only disconnect one nut on a gauge at a time to prevent it from moving around in the housing. The only insulation is a piece of cardboard, move the gauge out of center and the stud can short out on the housing.

[jmalloy]

I realize this is an old thread but felt the need to add a "me too"...

Eric's advise was spot-on. The fuel gauge on my 1980 Traveler was not working. Tightening the nuts on the back of the gauge fixed the problem. I'll replace the stamped nuts as suggested, but that will have to wait until tomorrow.

You guys are great!