I have an 85 jimmy the fuel sending unit is new the ground is clean on the frame my gauge reads past full I can move the needle back to empty once I turn I the key it goes past full most things I see say ground issue I have checked it is clean any other ideas
CK5
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Fuel gauge reading full
- Thread starter boo454
- Start date
Sending unit is junk most likely--my '82 GMC is doing the same thing,it pegs the fuel gauge needle at 3 o'clock position when the key is turned on,I tried grounding the tab on the sending unit,it did nothing..
I have a few other known good sending units hanging around ,and I was able to get the plug off the one on the tank and plug it onto one of the good ones,grounded it,and moving the float makes the gauge work normally--so its the sending unit thats junk..of course!..a simple ground wire would be too easy a fix...
..I had just put the tank in the truck too,and discovered it has some weepy spots also...was tempted to put my bic lighter to them and watch it burn...
I have a few other known good sending units hanging around ,and I was able to get the plug off the one on the tank and plug it onto one of the good ones,grounded it,and moving the float makes the gauge work normally--so its the sending unit thats junk..of course!..a simple ground wire would be too easy a fix...
..I had just put the tank in the truck too,and discovered it has some weepy spots also...was tempted to put my bic lighter to them and watch it burn...
How much fuel do you have in the tank? It is normal with a full tank for the needle to go past the full mark.
Did you diagnose it using this chart?...if the sender is new its possible its no good,but it could be something else like the wiring or the tank not being grounded good...http://forum.73-87chevytrucks.com/smforum/index.php?topic=25339.0
Scroll down to the fuel gauge section..
Scroll down to the fuel gauge section..
I haven't checked oms yet it was a diesel when I got it but put a dash cluster in it that has a gauge that says unleaded fuel only so no one would put diesel fuel in it by accident not sure if that would make a difference the sending unit was for a diesel truck the tank only has the ground for the sending unit should I put one on the tank it self
The diesel sending unit differs only because it has 3 hose nipples,one is the fuel feed to the engine (3/8" hose),the "return" line (1/4") and one "extra" one (5/16" hose) is for a fuel drain siphon to empty any water from the tank that GM put there factory (and few people ever use, or even know it exists!)..
The electrical part is the same far as I know, other than the diesel also has a "water in fuel" sensor added to the sending unit,but its not connected to the fuel level sender rheostat..
I used a sender from a gas powered truck to "test" my gauge and it worked OK..far as I know the dash gauge should be the same as a gas powered truck other than it having the "water in fuel" warning lamp and "diesel fuel only" on the gauge cluster...
The tank "should" ground itself through the straps and mounting brackets,but it wont hurt to try using a jumper wire with alligator clips to ground it good and test it..shine up the spots where the clips go with sandpaper to make sure it contacts good..
The electrical part is the same far as I know, other than the diesel also has a "water in fuel" sensor added to the sending unit,but its not connected to the fuel level sender rheostat..
I used a sender from a gas powered truck to "test" my gauge and it worked OK..far as I know the dash gauge should be the same as a gas powered truck other than it having the "water in fuel" warning lamp and "diesel fuel only" on the gauge cluster...
The tank "should" ground itself through the straps and mounting brackets,but it wont hurt to try using a jumper wire with alligator clips to ground it good and test it..shine up the spots where the clips go with sandpaper to make sure it contacts good..
Still should be a ground, sender to frame.
Yes,on my diesel there is a black ground wire on the sender unit plug,and a pink one for the fuel sender,a yellow one for the water in fuel sensor..the black wire "should" ground the sender,but there is a change the o-ring might prevent a good ground--very slim chance...after the lock ring and tank get rusty it could lose ground there--highly unlikely if its been disturbed recently though..
The ground terminal on the diesel sender was a flat spade type--on the one I used as a tester from a gas powered truck,it had a round "peg" style ground..my diesel wiring plug has all 3 wires in one,the gas one had just a spade for the fuel sender and the peg for a ground (or vise versa!).
I had tried grounding both the sending unit ground terminal and the tank itself,the gauge still buried at 3 o'clock--when I plugged in another good sender and grounded it to the frame,moving the float made the gauge work normally,so I assume it is the sender or the ground connection inside it is bad..
It would be unusual for a brand new sending unit to be "bad",but with todays quality control I would not be too surprised...lately I think factories just make parts that look "good",not always ones that WORK...
The ground terminal on the diesel sender was a flat spade type--on the one I used as a tester from a gas powered truck,it had a round "peg" style ground..my diesel wiring plug has all 3 wires in one,the gas one had just a spade for the fuel sender and the peg for a ground (or vise versa!).
I had tried grounding both the sending unit ground terminal and the tank itself,the gauge still buried at 3 o'clock--when I plugged in another good sender and grounded it to the frame,moving the float made the gauge work normally,so I assume it is the sender or the ground connection inside it is bad..
It would be unusual for a brand new sending unit to be "bad",but with todays quality control I would not be too surprised...lately I think factories just make parts that look "good",not always ones that WORK...
