I have read around and can't seem to figure this one out. If this is true, ~0V is full tank, ~8V is empty. The behavior of my CRD is as follows:



Sometimes works normally. When go over rough spots it can change. The SPAN of the range changes. So like it will go from 1/2 tank down to zero. It still seems linear. So for example it will go from 1/2 tank to zero, which is really full tank to half tank. Then the light comes on etc. A partial short on the output signal would indicate more FULL then more EMPTY. So what the heck kind of failure can this be? The linearity of it isn't changing, just the range, E-1/2 tank becomes what is in reality, 1/2 tank to FULL tank. I have been scratching head for months and years and can't seem to figure out how any kind of rubbing wire can cause this, or any other failure for that matter. A sticking float wouldn't behave this way would it? It would stay in one spot then jump or do something different, not what I'm experiencing. Any ideas? Thanks

Or maybe the source voltage is decreasing causing the output to decrease? But I would expect the LINEARITY would change say (full to zero tank in reality) it would show HALF to ZERO. Not the behavior I describe, right?

Could be the resistance on the fuel sending unit float is going bad or has fuel corrosion on the contacts. Have to drop the tank and pull the unit out and take a look.
Good time to install a in-tank lift pump if you haven't yet.

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05 CRD; Rebuilt top end w/ARP studs, EGR delete, SEGR, HD cooling fan, Samco hoses, in tank pump, JBA coil overs & control arms, KK clevis fork, 1/2" cradle drop, 1/4" motor mount lift, WJ rear upper trilink w/WW mount, WJ lower control arms, 4:10 gear, front/rear air lockers, ARB bumper, Rock Lizard sliders/roof rack, Mod T-stat

Mine would go to full, or empty, sometimes in between, changing the tank sending unit, and putting a Cummins lift pump at the same time fixed it for me.

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20 year owner of Libby CRD!
2006 LTD Bright Silver loaded with all the needed mods, CCV intact.
Equipped with HDS thermostat, plenty of heat, faster warm-ups, increased fuel mileage.