Inaccurate Fuel Gauge Reading, Gauge Indicates Fuel in Tank (Replace Fuel Harness Assembly)
| Subject: | Inaccurate Fuel Gauge Reading, Gauge Indicates Fuel in Tank (Replace Fuel Harness Assembly) |
| Models: | 2003-2005 Chevrolet Kodiak 6500-8500 Series |
| 2003-2005 GMC Topkick 6500-8500 Series |
| with Isuzu 7.8L Diesel (Non-CTF) (VIN 3 -- RPO LG4) Built Prior to January 1, 2004 or |
| CAT 7.2L Engine (VIN C -- RPO LG5) Built Prior to August 31, 2004 |
| with Dual Fuel Tanks |
Condition
Some customers/dealers may comment that there is an imbalance between the two fuel tanks that could result in fuel starvation. The fuel gauge indicates that there is adequate fuel in the tanks.
Cause
A low return flow in the fuel return lines may result in uneven fuel return to the tanks during idle and low speed operation.
These vehicles are equipped with a dual feed-dual return fuel system. Fuel return from the injection pump may not return evenly to both tanks. Over time, the fuel level in one of the tanks will drop below the end of the pick-up tube in the tank and the pump will then pull air into the system, causing fuel starvation. Because the fuel gauge shows the average level of fuel in both tanks, the fuel gauge will indicate that there is adequate fuel on-board.
Correction
Before diagnosing the fuel return system, inspect the vent tubes on the fuel tank sending units to verify that the tubes are open and free of debris.
If diagnosis leads to uneven fuel return at low speed or idle, replace the flexible fuel harness assemblies at both fuel tanks using the applicable part numbers below. The return lines of the new assemblies have a built-in orifice that increases the return line pressure and more evenly distributes return fuel to each tank.
Use the following procedure to replace the fuel harness assemblies:
Tools Required
J 44581 Fuel Line Disconnect Tool
Fuel Feed and Return Harness (Driver Side)
Fuel Feed and Return Harness (Passenger Side)
Disconnect the fuel feed and return harness assembly fittings (four connections each side) from the fuel sender and pipe connections for both fuel tanks. Refer to the arrows in the illustrations above. Refer to the Quick Connect Fitting(s) Service (Metal Collar) (SI Document ID #801166).
Connect the new Fuel Feed and Return harnesses to both fuel tanks. Refer to the illustrations above for hose orientation. The return line of the harness may have colored tape (1) affixed to one end of the hose. The colored tape end of the return line connects to the fuel sender. If colored tape is not present, look in the end of the small diameter return line for the orifice. Install this end to the sender tube.
Verify that there is fuel in the tank and that the fuel lines/connections are secure.
Verify that the fuel filter is properly installed.
Bleed/prime the fuel system. For the 7.8L engine, refer to Fuel System Bleeding (Non-CTF) (SI Document ID #835716). For the CAT 7.2L engine, refer to the CAT 3126 Unit Repair Manual for further information.
Clean any fuel that may have leaked/spilled onto the vehicle and floor.
Parts Information
Part Number | Description | Usage |
|---|---|---|
10361025 | Harness Asm-Fuel Feed & Return (LH) | NNQ/NPW (Standard Cab and Crew Cab) |
10361026 | Harness Asm-Fuel Feed & Return (RH) | NNQ/NPW (Standard Cab) |
10361027 | Harness Asm-Fuel Feed & Return (LH) | NG7 |
10361028 | Harness Asm-Fuel Feed & Return (RH) | NG7 |
10361029 | Harness Asm-Fuel Feed & Return (RH) | NNQ/NPW (Crew Cab) |
Parts are currently available from GMSPO.
RPO Description
RPO | Description |
|---|---|
CTF | 2004 Diesel Emission Standard |
LG4 | 7.8L 6 Cyl Duramax™ Diesel Engine |
LG5 | 7.2L 6 Cyl Turbo Diesel Engine |
NG7 | 102 L (25 Gal) Fuel Tank (RH) 200 L (50 Gal) Fuel Tank (LH) |
NNQ | 201 L (50 Gal) Steel Step Fuel Tank |
NPW | 144 L (35 Gal) Dual Steel Step Fuel Tank |
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation | Description | Labor Time |
|---|---|---|
L9705 | Harness, Fuel Feed and Return (Both Tanks) - Replace | 0.3 hr |
