Fuel Gauge

[KneeDeep]

This week I purchased my second XJ, a '90 Laredo. It's idle was terrible and couldn't hardly run. I've had a similar problem 2 years ago with my other XJ, a '96 Sport, which I resolved after troubleshooting by replacing the fuel filter and fuel pump sock.
The Laredo's sock looked brand-spanking new so I replaced it and reinstalled the pump. I had checked the plugs first thing this morning and found them all to be Autolite 3924 set at .45 - .48 so I regapped them to .35. The last thing I did was cleared the ECU just for kicks. When I gave her a test drive, the engine ran smoothly! (I was so glad I didn't have to remove the crankshaft position sensor!) But for some reason the gas gauge was reading way full when it only has about 1/8 of a tank. Is it possible that I have the float caught somehow on the fp? I'm sure the ECU has nothing to do with the gas gauge. Any thoughts? Should I pull the pump again tomorrow and check the float?

Thanks for your help!

[4.3LXJ]

Float stuck maybe. But a more likely scenario is the wire to the fuel gauge is grounded. The fuel gauge modulates the ground.

[Mudderoy]

This week I purchased my second XJ, a '90 Laredo. It's idle was terrible and couldn't hardly run. I've had a similar problem 2 years ago with my other XJ, a '96 Sport, which I resolved after troubleshooting by replacing the fuel filter and fuel pump sock.
The Laredo's sock looked brand-spanking new so I replaced it and reinstalled the pump. I had checked the plugs first thing this morning and found them all to be Autolite 3924 set at .45 - .48 so I regapped them to .35. The last thing I did was cleared the ECU just for kicks. When I gave her a test drive, the engine ran smoothly! (I was so glad I didn't have to remove the crankshaft position sensor!) But for some reason the gas gauge was reading way full when it only has about 1/8 of a tank. Is it possible that I have the float caught somehow on the fp? I'm sure the ECU has nothing to do with the gas gauge. Any thoughts? Should I pull the pump again tomorrow and check the float?

Thanks for your help!

I'm not clear on if you went inside the tank on the 90. If you did and the fuel gauge isn't changing I'd say it's a safe bet.

[KneeDeep]

Float stuck maybe. But a more likely scenario is the wire to the fuel gauge is grounded. The fuel gauge modulates the ground.

Hey, thanks for the reply. Are you talking about the wire on the gauge itself? I didn't bother any wires except the battery cables. I considered the float getting stuck but it worked freely when I pulled the pump and I don't think there's anything that it could be caught on.
If I do pull the pump, would it be easier to drop the tank? I've pulled XJ pumps before and can do it fairly quickly but I still cuss up a storm with that hog head blocking everything. Perhaps if I fill the tank completely it may dislodge the float. But if that doesn't work, I'll have to drain it to get back to it.

[KneeDeep]

I'm not clear on if you went inside the tank on the 90. If you did and the fuel gauge isn't changing I'd say it's a safe bet.

I initially removed the fuel pump to check the sock and after everything checked out good, reinstalled it all. After clearing the ECU I took it for a test drive which drove superbly, but I watched the gas gauge rise up past full and remained. If it's electrical problem, where would I check? I didn't touch any wiring today except the battery so I'm sure I didn't ground anything out or open a circuit anywhere.
I guess I'll just pull the pump again tomorrow.

[4.3LXJ]

Hey, thanks for the reply. Are you talking about the wire on the gauge itself? I didn't bother any wires except the battery cables. I considered the float getting stuck but it worked freely when I pulled the pump and I don't think there's anything that it could be caught on.
If I do pull the pump, would it be easier to drop the tank? I've pulled XJ pumps before and can do it fairly quickly but I still cuss up a storm with that hog head blocking everything. Perhaps if I fill the tank completely it may dislodge the float. But if that doesn't work, I'll have to drain it to get back to it.

You shouldn't need to drop the tank. While you have it out make sure the wire and beyond that goes to the rheostat for the gauge does not have direct grounds