1998 Chev truck gas gauge problem

[Old Iron nut]

Truck is 3500 Cheyenne model. Originally was equipped with dual tanks. Rear tank has been removed due to rusted out fuel lines. Front tank has had fuel pump and gas gauge sending unit with OE part (new). Unable to get gas gauge to work. Does the fuel pump balance module have to be used with a single tank or can it be phased out? Former fuel pump for rear tank has been removed as well the fuel level wiring for the rear tank. When hooked up to the new fuel level unit, and the ignition is turned on, the gauge will go past full quickly and fall back to empty. I have the manuals (four) from GM and have not found them to be much help. Anyone out there experienced similar problems? I there anyway that the gauge can be tested? Thanks in advance, Old Iron nut. PS. motor is 350 cid.

[esbstuff]

3500hd truck? I think those work as an average of both tanks... if one is missing that might be the issue. Check out 3500hd.com They should be able to answer that question easily...

[95 S_Trucker]

Yes, you have to remove the balance module/relay for the fuel gauge to work.

I had to remove the rear tank on my 96 cab/chassis truck. I connected the wires from the sending unit to the wires before the module. I can't remember the colors.

[95 S_Trucker]

Originally Posted by esbstuff

3500hd truck? I think those work as an average of both tanks... if one is missing that might be the issue. Check out 3500hd.com They should be able to answer that question easily...

FYI, dual tanks were available on all cab/chassis models. That would include 2500, 3500, and 3500hd.

[Old Iron nut]

95S Trucker, Been out trying to bypass that module and no luck. Cannot get the gauge to work. I can get it to work by wiring the 5 volt wire (gray) to the sending unit but after a few seconds, it drops back to nearly empty. There is 10 gallons in the tank so it should register about a quarter tank. If you have any more ideas I would hearing them. Cheers, Old Iron nut.

[95 S_Trucker]

I haven't gotten a chance to check the wiring under my truck yet.


I will get some diagrams. I will have to post them from a different computer.


You should be able to connect the gray wire(from the harness side of the front sending unit) to the purple and white wire before the balance module. If that doesn't work, we can do some more tests.

[95 S_Trucker]

What you have now:

[95 S_Trucker]

What you want:

[95 S_Trucker]

You can remove most of the wiring. If you have a fuel tank pressure sensor(California emissions) you will need to keep it. I would terminate the pink wire and wrap it up real good. That fuse powers some other circuits. So pulling the fuse will not work.

Before you cut all the wires, use a test lead and ground the purple/white wire. Then tell us what the fuel gauge does.

[Old Iron nut]

Message to 95 S Trucker, Thanks for the info. Following your schematics, I was able to sort the problem out. Also on the new fuel pump assembly they have changed the plug from a square one to a long rectangular one. The new electric connector number is GT280. On it you strip off the insulation for about 5/16" on the orange/black wire and do the same on the black wire. You twist the two together and insert them into a blue wire connector. Crimp the one end of the connector. Strip off about 5/16" of the vehicle harness black wire that went to the original fuel pump connector. Insert this wire into the blue connector and crimp it. Use heat gun to seal the connector. Connect the gray wire from the GT280 connector to the original gray wire from the fuel pump harness with a red connector, crimp and seal with a heat gun. The purple wire is not used. Tape it along side the harness and secure same.The rest of the wires from the fuel pump balance module may be cut off and secured to the harness.
When the key is turned on the gauge goes to full scale deflection and then comes back to zero. It then pulses to whatever the level is in the tank and stays there, the way a gauge should work.
Many thanks 95 S Trucker, my gauge is now working. Cheers, Old Iron nt.