Fuel Sender lost Calibration

[MIPS]

I had to replace my gas tank and that meant removing the fuel sender unit. Before it was removed it worked great and was accurate and ohm'd out fine per spec (248-31 ohms). I carefully removed and transplanted it into the new tank (because I know they are unobtanium) but after al that it seems to be out of spec now.

Full tank reads 3 ohms and pegs the needle WAY past the F. Empty tank with the sender arm resting on the end stop only goes to 156 ohms, which puts the gauge at about the 1/4 mark. Unplugging the unit entirely does as expected and the gauge falls to E, so the wiring and gauge itself are still good.
Slowly moving the float from full to empty and back doesn't show jumps or drop-offs, so there's no breaks in the pickup track but I can't see a calibration adjustment and I didn't roughhandle the unit so what gives?

[eaglefreek]

Could there be a ground issue?

[MIPS]

Verified that. The pigtail on the sender is good and I cleaned up around the bolt that secures it to the chassis. I know the battery/block to chassis ground is also good because I serviced that three months ago. Sender resistance is very much out of spec but inconsistent with a broken or shorted slider.

[djm3452004]

Galvin's AMC/Rambler has replacement fuel sending units for $139 plus shipping, P/N 04-0700.

American Parts Depot has them as well for $135 plus shipping, which is actually down like $20 from where it was a month or so ago if I remember correctly.  (P/N 936 1503J)


Hope this helps!

David

[MIPS]

I will keep that in mind, but for now I was correct and the internal slider has shifted. To disassemble the sender there's three metal tabs you need to pry up, then mark the current end stops for the lever (or you will lose your armature calibration) and straighten the end stops and the piece pops out. Inside is a very fine winding of nichrome wire and the copper slider. Note the cracked bushing that allows the slider to shift, which is currently my problem.





There's still some grip on the shaft which I think is all I can work with because I can't think of any adhesive that will survive immersion in gas so I was able to nudge it back where it should be, then reassemble and adjust back the end stops for a fairly good range of resistance again.

[DAVE]

don't know if this would work but maybe JB weld

[MIPS]

I would not trust it for long periods.
I think I'm just gonna keep suing it until it fails again, then install a new sender. I just need to make it through the weekend.