Hummer H1 (2006+). Manual - part 172

3-30 Fuel, Emissions, and Exhaust

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Fuel Injectors

A fuel injector is a solenoid device, controlled by the fuel injection control module (FICM), that meters pressurized fuel to a single
engine cylinder. The engine control module (ECM) energizes the low-impedance injector solenoid to open a normally closed 
valve. Fuel pressure is released from above the fuel injector pintle, and is returned to the fuel tank through the fuel return lines. The 
difference in fuel pressure above and below the pintle causes the pintle to open. Fuel from the fuel injector tip is sprayed directly
into the combustion chamber on the compression stroke of the engine.

Removal

1.

Disconnect the negative battery cable.

2.

Remove the air cleaner assembly and the air inlet hose.

3.

Remove the FICM (Refer to section 3).

4.

Prior to removing the fuel injector pipes, use compressed air to blow any debris from between the injector line and fittings.
Wipe the fittings clean of debris.

5.

Spray lithium grease, GM P/N 12346293 or equivalent, between the fuel injector line and fittings to assist in containing any
debris during removal. 

NOTE:

 DO NOT use compressed air to clean debris from the fuel injector inlet after the fuel line is removed. Using compressed

air can allow debris to enter the fuel injector inlet and damage the fuel injector.

6.

Remove the fuel injector pipes (Figure 3-13).

NOTE:

Label all the injector electrical connectors before the connectors are removed in order to prevent reconnecting to the wrong

injector. Failure to properly connect the injectors in the correct sequence will cause severe engine damage.

7.

Unplug the injector electrical connectors.

8.

Remove the fuel return hose clips.

9.

Remove the fuel return hose from the injectors (Figure 3-17).

10. Remove the fuel injector bracket bolts.

11. Install special tool J-46594 into the bolt hole in the fuel injector bracket.

12. Install a flare nut wrench onto J-46594 and pull back away from the fuel injector, until the injector releases from its seat.

13. Remove special tool J-46594.

14. Remove the fuel injectors and brackets.

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Figure 3-17:   Fuel Injector Return Hose

Fuel Injector Cleaning and Inspection

NOTE:

If reusing the old injectors perform the following steps.

1.

Use a soft bristle non-metallic brush and top engine cleaner, GM P/N 1052626 or equivalent, to remove any deposits from the 
nozzle tip (1) and the copper washer sealing area (2) before re-installation (Figure 3-18).

2.

Inspect the fuel injector nozzle tip (1) for any signs of discoloration (dark yellow, tan or blue) due to excessive heat.

3.

Replace the injector if any damage is found.

4.

Clean the fuel injector high pressure line.

5.

Inspect the fuel injector line for excessive corrosion or damage to the sealing surfaces. Replace the line if any damage is found.

FUEL INJECTOR

RETURN HOSE

3-32 Fuel, Emissions, and Exhaust

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Figure 3-18:

Fuel Injector Cleaning and Inspection

Installation

1.

If necessary, remove the fuel injector bracket pins.

2.

If necessary, remove and discard the copper washer from the fuel injector bore.

3.

If necessary, remove and discard the O-ring from the fuel injector.

4.

Install the fuel injectors with brackets

5.

Install the fuel injector bracket bolts and torque the bolts to 22 lb-ft. (30 N·m).

6.

Connect the fuel injector electrical connectors.

7.

Install the fuel return hose to the injectors.

8.

Install the fuel return hose clips.

9.

Install the fuel injector pipes, hand tighten both ends of the pipe.

NOTE:

Ensure proper torquing of the fuel injector line. An under-torqued fuel injector line will not seal properly and an over-

torqued fuel injector line may damage the fuel injector fitting. An improperly sealed or damaged fuel injector line or fuel injector
fitting will cause a fuel leak.

10. Torque the injector pipes to 30 lb-ft. (41 N·m).

11. Install the FICM (Refer to section 3).

12. Install the air cleaner assembly and the air inlet hose.

13. Bleed and prime the fuel system (Refer to section 3).

14. Start the engine and check for leaks.

FUEL TANKS, LINES, AND VALVES 

The main and auxiliary fuel tanks are made of high density polyethylene. Auxiliary fuel tank capacity is 24.5 gallons (92.7 liters).
Main tank capacity is 27 gallons (102.1 liters).

Quick connect fittings are used at most of the fuel line connection points. 

Fuel level transmitters for main and auxiliary tanks are mounted within the tanks. A selector valve, mounted on the passenger side
of the frame, controls tank flow and selection.

Vent lines are used at both tanks to avoid internal pressure buildup.

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 Fuel, Emissions, and Exhaust  3-33

Fuel return lines are used to send unused fuel from the nozzles and the injection pump back to the fuel tanks.

FUEL SELECTOR VALVE

The valve’s function is to switch fuel supply from the main to the auxiliary tank (and back) when needed (Figure 3-19). The valve
is electrically operated by a switch in the passenger compartment. The switch is mounted on the instrument panel. Quick connect
fittings are used to attach each of the six fuel lines to the valve. The valve is mounted on a bracket attached to the passenger side
frame rail. Valve position is forward of the main fuel tank and B-pillar area.

Removal

1.

Disconnect the fuel lines one at a time and tag them for reference (Figure 3-19).

2.

Remove the bolts retaining the valve mounting bracket to the frame.

3.

Disconnect the selector valve wiring connector.

4.

Remove the bolts securing the selector valve to the mounting bracket and remove the valve.

Installation

1.

Secure the selector valve to the mounting bracket with the bolts.

2.

Connect the selector valve wiring connector.

3.

Secure the mounting bracket to the frame with the bolts.

4.

Connect the fuel lines.

5.

Prime the fuel system.

6.

Start the engine and check for proper operation and for fuel leaks.