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Fuel Gauge

R

Rodd

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Location
Antelope, CA
I went to church this morning and my fuel gauge was working fine. Got in this afternoon to go to my parents house and the fuel guage was pegged passed full. I believe it does this when the FSU is unplugged. I checked it and it is still plugged in. The wiring all looks good I don't see any opens in the wire. Where do I look next?
 
Good question, I know most fuel/pickup sending units are grounded, I've never had the need to look for it.

It could be the one you mentioned but it seems far away.
 
ground is on the frame rail next to the tank,real sweat hart to get at.
A collapsed tank pegs out the gauge too,dont ask how i know.
 
bison said:
ground is on the frame rail next to the tank,real sweat hart to get at.
A collapsed tank pegs out the gauge too,dont ask how i know.
Click to expand...

I have had my tank down a few times and the only ground I saw was the one on the fill tube. Is it the same for burbs and pickup's?
 
i have done 3 pickup tanks and there was always a ground wire between the frame and the sending unit.
the ground you mention on the fill tube wont do any good to ground the tank cause of the hose to the tank.

Mebby a burb is wired diff,you might have a diff sending unit harnass with the ground going back to the front.
 
bison said:
i have done 3 pickup tanks and there was always a ground wire between the frame and the sending unit.
the ground you mention on the fill tube wont do any good to ground the tank cause of the hose to the tank.

Mebby a burb is wired diff,you might have a diff sending unit harnass with the ground going back to the front.
Click to expand...

My fsu doesn't have a ground wire. It must use one of the other grounds up front since that is where the cable runs to.
 
To the best of my knowledge:

It PEGS full when the Sending unit wire is grounded out.

When its unplugged it should go to the empty side.
 
From the install of my transfer flow tank: Cut the sensor wire. Verify you have the proper wire by the gauge reading full or over full. 1993 model pickup.

Some years may be different and run the gauge the other way when open. Open on 2007 and 2008 read empty as I recall.

If the wires are perfect and you have traced the wire loom back from the tank looking for that sneaky frame ground coming out of it...

More than likely your sensor in the tank has gone bad. Common GM issue. Will read good and then hit the bad spot pegging the gauge till the float moves to a good spot on the sensor wire. You can pull it out (Drop tank) and clean the sulfur/fuel additives/corrosion off the sensor resistance wire coil. Or just replace the sensor. They are kinda flaky after cleaning sometimes - this is not an area to be too cheap on.
 
WarWagon said:
From the install of my transfer flow tank: Cut the sensor wire. Verify you have the proper wire by the gauge reading full or over full. 1993 model pickup.

Some years may be different and run the gauge the other way when open. Open on 2007 and 2008 read empty as I recall.

If the wires are perfect and you have traced the wire loom back from the tank looking for that sneaky frame ground coming out of it...

More than likely your sensor in the tank has gone bad. Common GM issue. Will read good and then hit the bad spot pegging the gauge till the float moves to a good spot on the sensor wire. You can pull it out (Drop tank) and clean the sulfur/fuel additives/corrosion off the sensor resistance wire coil. Or just replace the sensor. They are kinda flaky after cleaning sometimes - this is not an area to be too cheap on.
Click to expand...

When I put in a new fsu about 3 years ago there were no sensors for the fuel gauge. The float up registers full and as the float lowers as fuel empties it registers empty.
 
Just a possible thing to check here. I replaced my FSU, found the PITA ground on the cross member above the axle. Cleaned it, hooked it back up, same issue. When full to top of filler neck the gauge would read half. Empty it pointed straight down.

Turns out my Sub had a dash "freak out" session where the gauges went haywire, moving erradically, and actually hit each other. I took the dash gauge cluster out, "reclocked" the oil pressure and fuel needles. Viola. Problem solved.

If none of the above work, this might be something to check.
 
Yup. Make sure you have either a completely empty (unlikely) or completely full tank of fuel first. Reposition needles being careful not to man-handle them. Reinstall cluster and turn vehicle on to see how the gauges read. I think it took 1 or 2 times of adjusting the needle position so make sure you don't completely reassemble the dash before checking.

EDIT: I made sure my fuel gauge went a lil bit past full. That's how it was before and if you don't do that it will go past empty before it is empty. Lesser of two minor evils...
 
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