GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC Suburban - 2WD 🢒 Engine 🢒 Engine Controls - 7.4L 🢒 Fuel System Cleaning

Fuel System Cleaning Fuel Tank

Removal Procedure

    Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  1. Disconnect the negative battery cable.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure .
  3. Drain the fuel tank. Refer to Fuel Tank Draining Procedure .
  4. Remove the fuel tank from the vehicle.
    5. • Refer to Fuel Tank Replacement (Suburban) for the Suburban.
    • Refer to Fuel Tank Replacement (Tahoe/Yukon) for the Tahoe/Yukon.
    • Refer to Fuel Tank Replacement (Pick-up - Side Tank) for the Pick-up.
    • Refer to Fuel Tank Replacement (Extended Cab - Side Tank) for the Extended Cab.
    • Refer to Fuel Tank Replacement (Cab and Chassis - Side Tank) for the Cab and Chassis with a side tank.
    • Refer to Fuel Tank Replacement (Cab and Chassis - Rear Tank) for the Cab and Chassis with a rear tank only.
    • Refer to Fuel Tank Replacement (4 Door Utility) for the 4DR. Utility.
  5. Remove the fuel gage sender and pump unit. Refer to Fuel Sender Assembly Replacement .
  6. Remove all remaining fuel from the tank.
  7. Inspect the fuel tank for any remaining fuel.

Cleaning Procedure

Important: 

   • Use only oil free compressed air to blow out the fuel pipes.
   • If the in-line fuel filter is plugged, replace it. Refer to In-Line Fuel Filter Replacement or In-Line Fuel Filter Replacement (Ex. Cart. Type 4-Door Utility) .

  1. Clean the fuel lines by applying air pressure in the opposite direction of fuel flow.
  2. Install tap water into the tank.
    3. • Move the tank to the flushing area (wash rack).
    • Agitate the water vigorously and then drain it.
  3. Install a gasoline emulsifying agent into the tank. Use an available emulsifying agent, such as Product-Sol No. 913 or the equivalent.
  4. Add water to the fuel tank.
    5. • Refer to the emulsifying agent specifications for the mixture ratio.
    • Fill the tank with water until it overflows.
    • Agitate the mixture for ten minutes.
    • Drain the tank completely.
    • Completely flush out any remaining mixture.
    • Drain the fuel tank.
    • No service is to be performed on a damaged fuel tank, replace it.

Installation Procedure
  1. Install the fuel sender assembly. Refer to Fuel Sender Assembly Replacement .
  2. Install the fuel tank into the vehicle.
    3. • Refer to Fuel Tank Replacement (Suburban) for the Suburban.
    • Refer to Fuel Tank Replacement (Tahoe/Yukon) for the Tahoe/Yukon.
    • Refer to Fuel Tank Replacement (Pick-up - Side Tank) for the Pick-up.
    • Refer to Fuel Tank Replacement (Extended Cab - Side Tank) for the Extended Cab.
    • Refer to Fuel Tank Replacement (Cab and Chassis - Side Tank) for the Cab and Chassis with a side tank.
    • Refer to Fuel Tank Replacement (Cab and Chassis - Rear Tank) for the Cab and Chassis with a rear tank only.
    • Refer to Fuel Tank Replacement (4 Door Utility) for the 4DR. Utility.
  3. Connect the negative battery cable.
  4. Check for fuel leaks
    5. 4.1. Turn the ignition ON for 2 seconds.
    4.2. Turn OFF the ignition for 10 seconds.
    4.3. Again, turn the ignition switch to the ON position.
    4.4. Check for fuel leaks.

Inspection Procedure

Important: The fuel tank filler neck clamps must be properly positioned and aligned. Otherwise, the filler neck may become disconnected from the fuel tank.

Turn the ignition switch ON for two seconds then turn the switch OFF for ten seconds. Again turn the ignition switch ON and check for fuel leaks.

Fuel System Cleaning Fuel Pipes

Removal Procedure

    Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  1. Disconnect the negative battery cable.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure .
  3. Drain the fuel tank. Refer to Fuel Tank Draining Procedure .
  4. Remove the fuel tank from the vehicle.
    5. • Refer to Fuel Tank Replacement (Suburban) for the Suburban.
    • Refer to Fuel Tank Replacement (Tahoe/Yukon) for the Tahoe/Yukon.
    • Refer to Fuel Tank Replacement (Pick-up - Side Tank) for the Pick-up.
    • Refer to Fuel Tank Replacement (Extended Cab - Side Tank) for the Extended Cab.
    • Refer to Fuel Tank Replacement (Cab and Chassis - Side Tank) for the Cab and Chassis with a side tank.
    • Refer to Fuel Tank Replacement (Cab and Chassis - Rear Tank) for the Cab and Chassis with a rear tank only.
    • Refer to Fuel Tank Replacement (4 Door Utility) for the 4DR. Utility.
  5. Remove the fuel gage sender and pump unit. Refer to Fuel Sender Assembly Replacement .
  6. Remove all remaining fuel from the tank.
  7. Inspect the fuel tank for any remaining fuel.

Cleaning Procedure

Important: 

   • Use only oil free compressed air to blow out the fuel pipes.
   • If the in-line fuel filter is plugged, replace it. Refer to In-Line Fuel Filter Replacement or In-Line Fuel Filter Replacement (Ex. Cart. Type 4-Door Utility) .

  1. Clean the fuel lines by applying air pressure in the opposite direction of fuel flow.
  2. Install tap water into the tank.
    3. • Move the tank to the flushing area (wash rack).
    • Agitate the water vigorously and then drain it.
  3. Install a gasoline emulsifying agent into the tank. Use an available emulsifying agent, such as Product-Sol No. 913 or the equivalent.
  4. Add water to the fuel tank.
    5. • Refer to the emulsifying agent specifications for the mixture ratio.
    • Fill the tank with water until it overflows.
    • Agitate the mixture for ten minutes.
    • Drain the tank completely.
    • Completely flush out any remaining mixture.
    • Drain the fuel tank.
    • No service is to be performed on a damaged fuel tank, replace it.

Installation Procedure
  1. Install the fuel sender assembly. Refer to Fuel Sender Assembly Replacement .
  2. Install the fuel tank into the vehicle.
    3. • Refer to Fuel Tank Replacement (Suburban) for the Suburban.
    • Refer to Fuel Tank Replacement (Tahoe/Yukon) for the Tahoe/Yukon.
    • Refer to Fuel Tank Replacement (Pick-up - Side Tank) for the Pick-up.
    • Refer to Fuel Tank Replacement (Extended Cab - Side Tank) for the Extended Cab.
    • Refer to Fuel Tank Replacement (Cab and Chassis - Side Tank) for the Cab and Chassis with a side tank.
    • Refer to Fuel Tank Replacement (Cab and Chassis - Rear Tank) for the Cab and Chassis with a rear tank only.
    • Refer to Fuel Tank Replacement (4 Door Utility) for the 4DR. Utility.
  3. Connect the negative battery cable.
  4. Check for fuel leaks
    5. 4.1. Turn the ignition ON for 2 seconds.
    4.2. Turn OFF the ignition for 10 seconds.
    4.3. Again, turn the ignition switch to the ON position.
    4.4. Check for fuel leaks.

Inspection Procedure

Important: The fuel tank filler neck clamps must be properly positioned and aligned. Otherwise, the filler neck may become disconnected from the fuel tank.

Turn the ignition switch ON for two seconds then turn the switch OFF for ten seconds. Again turn the ignition switch ON and check for fuel leaks.