<-Tis the YZ SeasonWOOHOO
Join Date: Oct 2007
Location: So Cal
Re: Fuel Gauge Stuck on Full (help)
I've checked my wiring diagram book (although it's for a 2000, it should be same as yours).
First, forget the aftermarket gauge! Try to troubleshoot/fix the factory one.
The fuel gauge gets its power (+12 volts) from a red/yellow (red with yellow stripe) wire. It feeds multiple items in the instrument cluster (Door ajar light, seat belt indicator, wait-to-start indicaor, etc.). So, if these are working, then the cluster should be supplying power to the gauge as well. It is supplied by fuse #19 in the fuse panel.
The gauge cluster has 3 harness plugs. The sender wire passes through one of these plugs (C250b) at the back of the cluster.
The wire from the sender to the gauge cluster (instrument cluster) is identified as a Yellow/White (YE/WH) (yellow with white stripe). It runs from the cluster to the tank sender (assuming you don't have dual tanks). It does pass through a couple of additional harness connectors between the tank and the dash.
The other side of the sender is grounded. The sender resistance should be ~145 ohms (tank FULL) to ~22.5 ohms (tank EMPTY).
Here's what I suggest:
Start at the fuel tank. Using an Ohmeter (or digital VOM): check the resistace of the sender (to ground), with the wire disconnected. Make sure it's not shorted or open. The resistance should be between the limits stated above (A half-full tank should be around 80-85 ohms). If reading is zero, the sender is shorted. If the reading is infinite (no reading), then the sender is open. Either of these means a bad sender. Replace it.
Next: Check he continuity of the wire from the tank to under the dash. This is the hard part!
You'll need to find the wire in the loom as close as possible to the instrument cluster (this will likely require pulling the cluster out). As I said above, it will be a yellow wire with white stripe (YE/WH).
With both the sender-end and cluster-end disconnected (unplugged from the cluster), check the continuity to ground. It should be infinite, no reading. This will prove that the wire is not shorted to ground.
Next: short one end to ground (the tank-end might be easiest to short). Now, take a reading from the other end of the wire to ground. The reading should now be zero ohms (or close to it: Less than 1 ohm). This will prove that the wire is not open.
These tests will determine whether the wiring is good, shorted, or open, and whether the sender is good, shorted, or open. If all tests come out good, then you most likely have a bad gauge. Unfortunately, the gauge is contained as part of the solid-state circuitry that makes up the instrument cluster. You would have to replace the cluster as a unit (junkyard item, maybe?).
If the wiring continuity checks show a short-circuit or an open in the wiring, then you will have to trace the wire through each of the harness connectors in the system. It's a bitch! Or, you could try stringing a new wire from the tank sender to the back of the cluster...either way, it's a bitch!
Hope this helps. Good luck...
Al in SoCal
2000 F350 C-C SRW 4x4 6-Spd
The Usual Stuff: AFE Intake, 38R Turbo, Big IC, Stealth Big oil, Stock AD Smokesticks, DP F5 Chip & PCM: "Live Tuned", Custom Fuel System, Non-EBPV Pedistal , 'T444' CCV, 4" S/S exhaust, Dual "Aussie" Stacks, SB Double-disc clutch