Fuel Gauge reading 1/4 off

[wally426ci]

68 D100 - stock in-cab tank

I've had this issue for a long while and just deal with it but I'd like to get it right.

My tank reads 1/4 tank too high; so when it shows 1/4 tank, I am essentially empty. When I fill it up, it goes above Full.

Recently I tried bending the float arm in the direction that it is already bent in order to basically lower its position on the range of the span. That did not change much and if anything made it a little worse......

Any ideas? I have another sender which I believe to be 69 (straight pick-up tube) I believe this one gets me a little closer but need to double check again. I plan on working on it over the weekend to soldier the junction of the tube to the sender plate so I wouldn't mind fixing this issue while in there.....

[Jims68]

Just a thought... maybe it is a bad gauge? Do an ohm reading for the Range on the sender unit next time you have the it out.

[wally426ci]

I am thinking it could be the sender because this is my 2nd or 3rd fuel gauge? I will ohm test it but I won't get the gauges pulled before carlisle

[Jims68]

I am thinking it could be the sender because this is my 2nd or 3rd fuel gauge?

This makes me wonder... why? Hmmm.... voltage? Is it wired correctly (meaning, has anyone made any funky repairs of the harness). Yeah, I know it is a lot to look at in the amount of time when going to Carlisle!

I think I have a spare sending unit, I'll see what the Ohm readings are on that.

[GMAN69]

You said you bent float arm, your post said you bent it the direction it was already bent .it would need to bend it up.

[wally426ci]

yes, it is already bent upward "V" from the factory so I continued that bend.

[wally426ci]

I am thinking it could be the sender because this is my 2nd or 3rd fuel gauge?

This makes me wonder... why? Hmmm.... voltage? Is it wired correctly (meaning, has anyone made any funky repairs of the harness). Yeah, I know it is a lot to look at in the amount of time when going to Carlisle!

I think I have a spare sending unit, I'll see what the Ohm readings are on that.

Thanks Jim. I will keep everyone posted. Hasn't changed from harness to harness either. All wiring is in great shape.

[Jims68]

OK... first I have to say that this pickup/sending unit came out of a 1970 D200, although, from what I "remember" they were the same length as the 68 trucks. Here is what I found (after I got it working). It was dirty from the old gas residue so I took it apart and carefully cleaned the wire and the contact. CHECK your contact inside to see if that is going all the way from end to end. Maybe that is bent somehow...????? Then, make sure you bend the wire BACK to the original "set".

FULL - 71
HALF (approx half tank) - 90
EMPTY - 127

Your mileage may differ

[powerwagon54]

68 and 70 senders are not the same. 70 is longer. I believe the ohms are the same, but 70 will not fit 68.

[Jims68]

68 and 70 senders are not the same. 70 is longer. I believe the ohms are the same, but 70 will not fit 68.

That is why I put my "Remember" in italics in my last post. The old memory slips sometimes

Thanks for the confirmation

[wally426ci]

Thanks yall. Wrenching tomorrow