Hi, I have a 2001 dodge 3500

Cummins diesel.I have a dead fuel gauge issue that doesn't seem quite like the others that I have researched,so I could use some help. It reads empty at all times, UNLESS I unplug the batteries for 15-20 minutes and let the truck reset. At this time the fuel gauge will read full for about 15 mins, before it slowly drops to empty again and stays there permenantly. Here is what I have done. I have dropped the tank and I have replaced the entire canister/float/fuel level sending unit. I used an volt meter on the new sending unit and as I moved the float up and down I watched the resistance change. I have done the gauge test and watched the gauge move through its full range of motion. I have also looked at the wiring harness underneath the front driver wheel well where the wires are exposed before they enter the harness, and the wires above the fuel tank to look for any breaks in the connection. I have a fass fuel pump and fuel pressure gauge and everthing reads normal as far as that is concerned.  Any ideas? Thanks for your time. 

Do you guys know off hand which of the wires is the ground for the sending unit. At the top of the tank the connector has a red and two greens. I would like to jump the ground directly to the frame and see what happens, but I don't wanna do the wrong one?

Edited July 30, 20168 yr by Atcmcc

That is weird your wiring harness FUEL TANK MODULE (DIESEL) plug doesn't follow any of the coloring codes i got in the 01 service manual.

 

FUEL TANK MODULE (DIESEL) - LT GRAY 4 WAY
CAV |   CIRCUIT            | FUNCTION
1      |  - - - - - - - - - - - -|
2      | K4 20BK/LB        | SENSOR GROUND
3      | K226 20DB/WT   | FUEL LEVEL SENSOR SIGNAL
4      |  - - - - - - - - - - - -|

 

Now I wonder if you have the lift pump retro fit inside the fuel tank installed by Dodge dealer?

Two things. @Chris O.

 

one, this truck did have the retrofit but it has since been removed and replaced with a fass fuel system. Also this is a pic of the y harness coming off of the fass pump and plugs directly into the top of the tank,so that would be why it's different colors. I should have taken a pic of the harness coming directly from the truck. I will do that and post here, sorry for my oversight.

A good volt meter can tell you which is ground, but disconnect the batteries first and set the VM to OHMs. Touch one probe to the frame and the other probe in the end of each wire. The ground will have Zero Ohms but double check too cause some OHMs can show up just from dirt on the frame etc.

 

 PLEASE , anyone correct me If I'm wrong

Oh yeah, theres another ground going from the PCM  to the firewall. I redid that one with heavy gauge marine wire. for better protection.

Edited July 31, 20168 yr by JAG1