Speaking of M38A1 Fuel Gauges...

acengraver · Post by **acengraver** » Tue Apr 21, 2009 7:56 am

I'm finally driving my M38A1 with some confidence. Everything seems to be working perfectly except the fuel gauge. I have downloaded the Gauge Troubleshooting info on this site. When I tested the gauge prior to installation it tested OK. When I tested the sender, it worked according to specs. When installed, however the gauge never reads more than about half full. I removed the sender wire from the sender at the tank and grounded it briefly. The gauge pegs at the full end. The tank ground is good, though I like your idea of a seperate ground from the earlier question. When I checked the ohms at the sender it showed 13.6 ohms and rocking the Jeep made it vary slightly higher or lower, as you would expect. According to the gauge/sender data that should make the gauge show a little less that half a tank, which it does. The tank is almost completely full, though. I'm thinking of pulling the seat and removing the sender as my next step, to make sure it isn't binding or rubbing on the inside of the tank. Anybody got any other ideas as to how to approach this problem?

MODIFIED · Post by **MODIFIED** » Tue Apr 21, 2009 8:00 am

I'd double check for good ground contact between the gauge> back of instrument panel> dash panel>body> and so on?

acengraver · Post by **acengraver** » Tue Apr 21, 2009 5:30 pm

I'll give that a try tonight.
Thanks

Jeeps4Brains · Post by **Jeeps4Brains** » Tue Apr 21, 2009 7:10 pm

When we restore these things we have a tendency to paint everything better.

What? I am just trying to make it last longer.

MODIFIED · Post by **MODIFIED** » Tue Apr 21, 2009 11:16 pm

ha

our own aesthetics can create such misery.

acengraver · Post by **acengraver** » Thu Apr 23, 2009 5:12 pm

The ground was sound. The gauge tests OK, following the normal test procedure. I disconnected the sender wire at the tank, inserted a 25 ohm potentiometer between one of the sender screws on the tank and the sender lead going to the gauge and the needle moved according to the position of the pot. In other words, the lower the ohms, the lower the gauge reading. I didn't have a pot that would go to 40 ohms to test full. The sender is showing about 10 ohms resistance even though the tank is practically full. Next I'll remove the sender and see if it is sticking, rubbing or if the float has a hole in it.