Fuel Gauge

[bikernut]

My 2003 GMC 3500 dually dump truck 6.0 engine and Auto Trans had a 1/4 tank of fuel last Sunday when I parked it. When I started it yesterday (Friday) the fuel indicator says empty and the low fuel lamp is lite. I went and filled up and guess what it still says empty after putting in $140 worth of fuel. I checked and both tanks are connected. Unplugging them does nothing for the gauge it still reads empty. When you first turn on the key after it sets a bit the gauge will get about 3/8 tanks and heads back to empty. if you shut it off and try without waiting a bit the needle doesn't move, you have to wait a while. I was under the assumption that if the wire was unhooked the fuel gauge goes to empty and if you ground it it goes to full or is it the other way around?
Any one have any ideas?
thanks

[shawno72]

Get ready to replace your fuel pump assembly. We have been doing a lot of the GM trucks from the 00-03 era. Common problem.

[bikernut]

this has dual tanks so how will I know which one is bad?
Thanks

[shawno72]

Fuel System - Cranks But No Start/Inaccurate Fuel Gauge


Bulletin No.: 04-08-49-018E

Date: January 05, 2005

TECHNICAL

Subject:
Cranks But No Start, Stall, Inaccurate/Incorrect Fuel Gauge Reading, No Fuel, Vehicle is Out of Fuel and Fuel Gauge Reads Above Empty (Replace Fuel Level Sensor)

Models:
2001-2004 Cadillac Trucks
1999-2004 Chevrolet and GMC Trucks

with Gasoline Engine (VINs Z, X, V, T, U, N, G, 6, 8 - RPOs LU3, LR4, LM7, LQ4, LQ9, L59, L18,LK5 L52)

Attention: Parts are currently available for vehicles with Variable Fuel (VIN Z - RPO L59) vehicles. Please refer to Corporate Bulletin Number 04-06-04-01 2B or newer for Variable Fuel (VIN Z - RPO L59) vehicles.

Supercede:

This bulletin is being revised to include information on the Chevrolet Colorado and the GMC Canyon. Please discard Corporate Bulletin Number 04-08-49-018D (Section 08 - Body and Accessories).

Condition

Some customers may comment on the vehicle stalling and will not restart, vehicle ran out of fuel, vehicle appears to be out of fuel but the fuel gauge reads above empty. The fuel gauge may read 1/4 tank.

Cause

Contamination on the fuel sending card may cause inaccurate/incorrect fuel gauge readings.

Correction

Follow the service procedure below for diagnosis and repair of this concern.

1. Confirm that the vehicle is actually out of fuel.

^ If the vehicle is not out of fuel but Engine Cranks but Does Not Run, refer to the appropriate Service Information.

^ If the vehicle is out of fuel and the gauge does not read empty, test the fuel gauge. Refer to the following information:

- Fuel Gage Inaccurate or Inoperative Single Tank

- Fuel Gage Inaccurate or Inoperative Dual Tanks

- Fuel Gage Inaccurate or Inoperative Colorado and Canyon


2. If testing reveals that the fuel gauge is operating correctly, replace the fuel sensor assembly and auxiliary tank fuel level sensor if equipped.

3. Replace the fuel level sensor. Refer to the following appropriate service information:

^ Fuel Level Sensor Replacement 4.8L and 5.3L Engines

^ Fuel Level Sensor Replacement 6.0L Engine - Front Tank

^ Fuel Level Sensor Replacement 6.0L Engine - Rear Tank

^ Fuel Level Sensor Replacement 8.1L vehicles with Front Tank

^ Fuel Level Sensor Replacement 8.1 L vehicles with Rear Tank









Parts Information

Parts are currently available from GMSPO.

Warranty Information







For vehicles repaired under warranty, use the table.







Disclaimer










© 2011 ALLDATA LLC. All rights reserved.
Terms of Use

[shawno72]

Here is a technical service bulletin I pulled off of Alldata. As for which tank I do not know how to test that.

[bikernut]

the truck runs and starts fine it does show a P0300 code for a miss fire and idles rough but runs down the road great.

[shawno72]

Take care of that misfire cause it can ruin a catalytic converter. And all I am saying is that you are at the beginning stages of a possible fuel pump failure. The TSB states that you can replace just the fuel level sender and not the whole assembly. You need to isolate which tank is reading wrong.

[bikernut]

will I unplugged both tanks and plugged in the front one and it didn't change so I will go back and unplug the front tank and see if the gauge will read correctly. Can I run on just 1 tank or do both have to be hooked up to run the vehicle?
the misfire is going to be taken care of on Tuesday.
thanks

[shawno72]

I think as long as the main tank, usually the front tank, is hooked up you should be ok.

[bikernut]

I just had the OBDII read and it is throwing a code P1172 low fuel transfer or some thing like that, would that have a bearing on the fuel gauge reading empty?

[bikernut]

it almost acts like the ground is not grounding, but where would that be? Which color wire is the ground at the tank, I think it should be black but I have been mistaken before so I don't want to just ground any old wire before I know for sure.
thanks

[shawno72]

Originally Posted by bikernut

I just had the OBDII read and it is throwing a code P1172 low fuel transfer or some thing like that, would that have a bearing on the fuel gauge reading empty?

That code may throw if you leave one of the tanks disconnected.

[bikernut]

I didn't run the truck just turned on the key, will that also throw a code?

[gmclowsierra]

the computer takes a reading of both tanks and averages it out. meaning if the front tank is full and the rear tank is empty its only going to read a half tank or a little more. when you put gas in it and it started to act up was the truck running or did you have the key on? either one will make it throw the code. as far as the code th e ecm commnds the rear pump on to transfer the fuel to the front tank so they re equal. if the ecm doesnt see a change in a certtain amount of time the ecm commands the rear pump off and illuminates the check engine light. usually it also makes fuel gauge go to empty. i would clear the codes and see what happens. as far as corrosion on the fuel card i would add some gm fuel system treatment to both tanks. the stuff actually helps to clean the fuel level sensor.

[bikernut]

I parked the truck and had no low fuel indicator light on and it had a bit over 1/4 full on gauge. started it and the low fuel light came on and gauge went to about 3/8 full and then drops back to empty real quick. it started acting up as soon as I started the truck from setting for a few days and showing no fuel in tank so then I went and filled it but it is still empty.

[bikernut]

all fixed, I had the code removed and it is back to normal. I think I know how the code set is that I parked it at one hell of an angle and when the transfer pump tried to pump from the rear tank to the front there was nothing there so I got the code for low transfer fuel pressure.
thanks for all the info and help!

[shawno72]

Great I am glad to hear all is well. Hopefully this was a one time incident.
Posted via Mobile Device

[bikernut]

it will be I hope as I won't park it in the same place when it is so low on fuel.
thanks