Fuel guage troubles

[Indydirtfarmer]

Trouble in paradise.... [img]/forums/images/graemlins/tongue.gif[/img] [img]/forums/images/graemlins/crazy.gif[/img] [img]/forums/images/graemlins/frown.gif[/img]

Last week, as we were finishing up planting a corn field, the fuel guage on my '78 Deere 2440 started doing strange things. It began flipping back and forth between full and empty. (with a relatively full tank) It seemed to do it worse with high engine RPM's or higher ground speeds (on the road) [img]/forums/images/graemlins/crazy.gif[/img] [img]/forums/images/graemlins/shocked.gif[/img]

Fast forward to yesterday... I had to do some bush hogging around the homestead. I fueled up the 2440. (I didn't pay any attention to the guage BEFORE fueling) When I started mowing, I noticed the fuel guage was dead on empty. (with full tank) When I shut off the tractor (to eat dinner) it jumped to full. When I fired back up to finish, it went back to empty... [img]/forums/images/graemlins/confused.gif[/img] [img]/forums/images/graemlins/frown.gif[/img]

Obviously a PROBLEM. [img]/forums/images/graemlins/frown.gif[/img] [img]/forums/images/graemlins/crazy.gif[/img] [img]/forums/images/graemlins/wink.gif[/img] [img]/forums/images/graemlins/tongue.gif[/img]

I have the owners manual, shop manual, and parts manuals to this tractor, but haven't had a chance yet to get them out for a look-see.

Now here's where you come in.. Any one know how I go about checking (1) the sending unit? (2) the guage? Is that guage "fuse protected" in any way? I'll check the wiring between the sending unit and guage when I get home this afternoon. [img]/forums/images/graemlins/tongue.gif[/img]

Anyone have any advice? [img]/forums/images/graemlins/confused.gif[/img]

Thanks in advance! [img]/forums/images/graemlins/grin.gif[/img]

Bill

[ducksjunk]

Bill;
Check the wiring to the gauge as well. Don't overlook the ground on the sending unit. Easy check. Run a separate jumper lead fron the sender body to a known good ground.
To test the sender itself, out of the tank, connect ohm meter to the terminals, and slowly raise/lower the float. You should see a steady change in the resistance with no spikes to infinity. I'd be surprised if it is the sender. A bad spot in the sendinr resistor should correct itself as the fuel level goes down moving the wiper past the bad spot. My best guess is a bad ground. Most common problem.
Richard.

[normde2001]

If you have other gauges that fluctuate, It's probably a bad ignition switch, (or especially if no other gauges).

[KiotiJohn]

Sure sounds like an intermittent ground problem which would explain why the bumping around makes it worse. Possibly only a loose ground connection, that is occasionally not grounding. If it were another wire, hot, you'd probably blow a fuse. So I'd go for checking the grounding first.
John

[frank_f15]

will 2nd KiotiJohn's theory. if not a bad ground, look for a partially broken wire, no telling how those wires are after many hours of use.