houdel

Cabell - I have been using the dipstick method since I got my Deuce in February. Even calibrated it in gallons, taking into consideration that the truck runs out of fuel with 10 gallons still left in the tank. I guess the military decided to mount the pump pickup about 2" above the bottom of the tank for a little safety margin to allow water & other crud to collect when refueling under less than ideal tactical conditions.

I woudn't be in too great of a rush to pull that fuel sender. I did a quicky run through the diagnostics procedure the first time and came to the erroneous (I believe) conclusion I had a bad fuel sender. The second time through I was a bit more carefull in my procedure, and now believe the problem is in the gauge itself. I just ordered a new fuel guage from Saturn, so I'll know in a couple of days if I was right about the gauge being defective. I assume you've also run the diagnostics, but here is my comprehensive, but fairly simple to perform process to assess if the problem is the gauge or sender:

1. Ignition on, remove wire 28 from the sender. Fuel gauge should read "Full". Ground wire 28 to the negative battery terminal. Fuel gauge should read "Empty". Measure voltage at wire 28, should be 24-28V. Measure resistance from sender to the negative battery terminal, should be nominally 0 Ohms.

2. Get a 0-30 Ohm potentiometer (you can use a higher rated potentiometer, but 31.5 Ohms is the max resistance of the sender unit, anything higher will give a "Full" reading on the fuel gauge) (or use individual resistors, 10 Ohm, 20 Ohm and 30 Ohms). Ignition on, connect one lead to wire 28, the other lead to the negative battery terminal. Vary the resistance from 0 to 30 Ohms, the fuel guage should read proportionaly to the resistance in the circuit from "Empty" to "Full". If the fuel gauge responds proportionally to the resistance used, the gauge most likely is OK. If it doesn't, the gauge is probably bad.

3. If you didn't get 0 Ohms between the sender and the negative battery terminal, you have a bad ground to the sender. Repair and retest.

4. If you didn't get 24-28V at wire 28, time to pull out the gauge panel and check the continuety of wire 28. Disconnect wire 28 from the fuel gage and the sender. Measure the resistance of wire 28 from end to end, it should be nominally 0 Ohms (mine read 0.3 Ohms). If wire 28 shows any significant resistance, repair or replace it. If the continuety is good, time to check the fuel gauge itself.

5. Ignition on, pull wire 27 from the fuel gauge and measure the voltage, you should have 24-28 V. If not, find the problem and fix it. If you do have 24-28V present at wire 27, reconnect it to the fuel gauge and run a jumper wire from one of the gauge mounting studs to a good, reliable ground, like the negative battery terminal. Check the voltage at pin 28 of the fuel gauge, you should have 24-28V. If you do, the gauge is probably good and the problem is in the sender. If you don't have 24-28V at pin 28, most likely the gauge is bad.

Hopes this helps, maybe you won't have to pull that fuel sender after all.