Hummer H1 (2006+). Manual - part 170

3-22 Fuel, Emissions, and Exhaust

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Figure 3-13:   High Pressure Lines

CONNECTING

HOSE (TYPICAL)

INJECTORS

CAP

NIPPLE

FUEL RAILS

INJECTOR

PIPE

FUEL RAIL

INLET PIPE

FUEL BALANCE

PIPE

FICM

GLOW PLUG 

CONTROLER

FUEL PRESSURE

SENSOR

RELIEF

VALVE

FUEL TEMP

SENSOR

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 Fuel, Emissions, and Exhaust  3-23

Fuel Injector Pipe Replacement

Removal

1.

Disconnect the negative battery cable.

2.

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.

3.

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.

4.

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

Installation

1.

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.

2.

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

3.

Bleed and prime the fuel system.

4.

Start the engine and check for leakes.

Fuel Balance Pipe Replacement

Removal

1.

Disconnect the negative battery cable.

2.

Disconnect the fuel rail balance pipe from the fuel rails.

3.

Remove the fuel rail balance pipe retaining bolts (Figure 3-14).

4.

Remove the fuel rail balance pipe.

Installation

1.

Connect the fuel rail balance pipe to the fuel rails.

2.

Torque the fittings to 30 lb-ft. (41 N·m).

3.

Install the fuel rail balance pipe retaining bolts and torque to 18 lb-ft. (25 N·m).

4.

Bleed and prime the fuel system.

5.

Start the engine and check for leaks.

3-24 Fuel, Emissions, and Exhaust

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Figure 3-14:   Fuel Rail Balance Pipe

FUEL BALANCE

PIPE

BOLT

CLIP

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 Fuel, Emissions, and Exhaust  3-25

Fuel Return System Diagnosis

 The Fuel Return System routes fuel from the fuel injectors and the fuel injection pump. The FRP relief valve is located in the rear
of the left common rail. The return fuel travels to the fuel cooler and then to the fuel tank. This fuel is used to cool and lubricate the
injection pump and the injectors.

 Fuel Return System Diagnosis

STEP

ACTION

YES

NO

    1

NOTE:

Do not apply more than the specified air pressure to the return line.

NOTE:

Ignition must be on for the fuel selector valve to switch.

1.

Switch the fuel selector valve to the main tank.

2.

Disconnect the return line at the engine.

3.

Remove the fuel filler cap from the main tank filler tube.

4.

Apply 1 psi air at the fuel return line that leads back to the tank.

5.

Listen at the filler tube for air flowing from the tank.

6.

Switch the fuel selector valve to the auxiliary tank.

7.

Remove the fuel filler cap from the auxiliary tank filler tube.

8.

Apply 1 psi air at the fuel return line that leads back to the tank.

9.

Listen at the filler tube for air flowing from the tank.

Did air flow from both of the filler tubes?

Go to step 10.

Go to step 2.

    2

Did air flow from one of the filler tubes?

Go to step 5.

Go to step 3.

    3

1.

Disconnect the fuel return line from the engine to the fuel selector valve.

2.

Apply 1 psi air at the fuel return line.

Did air flow from the line?

Go to step 4.

Go to step 8.

    4

1.

Disconnect the fuel return line from the fuel selector valve to the main 
tank.

2.

Remove the fuel filler cap from the main tank filler tube.

3.

Apply 1 psi air at the fuel return line that leads back to the main tank.

4.

Listen at the filler tube for air flowing from the tank.

5.

Disconnect the fuel return line from the fuel selector valve to the auxiliary 
tank.

6.

Remove the fuel filler cap from the auxiliary tank filler tube.

7.

Apply 1 psi air at the fuel return line that leads back to the tank.

8.

Listen at the filler tube for air flowing from the tank.

Did air flow from both of the filler tubes?

Go to step 5.

Go to step 6.

    5

1.

Replace the fuel selector valve.

Did you complete the replacement?

Go to step 10.

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    6

1.

Disconnect the return line at the fuel sender assembly that DID NOT have 
air flowing. 

2.

Retest using 1 psi at the fuel return line back to the tank.

Did air flow from the line?

Go to step 7.

Go to step 9.

    7

Replace the fuel sender assembly.

Did you complete the replacement?

Go to step 10.

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