How to Replace a Fuel Sending Unit in a GMC Sonoma

Replace the fuel-sending unit on your GMC Sonoma.

The fuel-sending unit on your GMC Sonoma is located inside the fuel tank. This unit is equipped with an arm that extends down into the tank and connects, through a variable resistor, with the fuel gauge on your instrument panel. In many cases, problems with the variable resistor makes replacement of the sending unit necessary.

Things You'll Need

• Shop rag
• Small screwdriver
• Fuel container
• Hand siphon pump
• Floor jack
• 2 jack stands
• Ratchet and socket
• Ratchet extension
• Spanner wrench
• New sending unit O-ring

Instructions

Relieve the fuel system pressure

1. Open the glove box compartment and locate the fuel pump relay behind the plastic cover in the upper left corner. This applies to 1995-97 2.2L engine models. For any other model go to step 5.

2. Unplug the relay on the far left.

3. Start the engine until it stalls.

4. Disconnect the black, negative battery cable. Then go to the next section.

5. Locate the Schrader valve on the inline of the fuel rail, right before the first fuel injector. The valve is similar to an air valve on a bicycle tire.

6. Cover the valve with a shop rag to catch the squirt of fuel as you depress the stem inside the valve with a small screwdriver.

7. Remove the black, negative battery cable.

Removing the Fuel Sending Unit

1. Loosen the fuel filler cap.

2. Drain the fuel tank through the fuel filler neck into an approved fuel container using a hand siphon pump, if necessary.

3. Raise the rear of your Sonoma vehicle using a floor jack and support in on two jack stands.

4. Disconnect the fuel filler hose from the tank using a ratchet, ratchet extension and socket.

5. Support the fuel tank with the floor jack and disconnect the tanks straps using the ratchet, ratchet extension and socket.

6. Lower the fuel tank just enough to gain access to the fuel lines, vapor hose and electrical connection on top of the tank.

7. Remove the fuel lines and vapor hose connected to the top of the fuel sending unit assembly by pressing the lock tabs on the plastic connectors and pulling the lines from the fuel sending unit fittings.

8. Unplug the fuel pump electrical connector from the top of the fuel-sending unit.

9. Lower the fuel tank.

10. Turn the lockring holding the fuel-sending unit onto the tank. Use a spanner wrench to turn the ring counterclockwise until the locking is free.

11. Lift the sending unit assembly carefully off the fuel tank and discard the O-ring located underneath the sending unit flange.

Installing the Fuel Sending Unit

1. Remove the fuel pump from the old sending unit and install it on the new sending unit.

2. Set the new sending unit in place using a new O-ring and turn the lockring clockwise using the spanner wrench.

3. Raise the fuel tank with the floor jack just enough to connect the fuel lines, vapor hose and plug the fuel pump electrical connector.

4. Set the fuel tank in place and install the tank straps using the ratchet, ratchet extension and socket.

5. Connect the fuel filler hose to the tank using the ratchet, ratchet extension and socket.

6. Lower the vehicle.

7. Refill the tank and tighten the fuel filler cap.

8. Connect the black, negative battery cable.

9. Start the vehicle and check for leaks.

Tips & Warnings

• Make sure to park your car away from appliances with open flames like dryers and water heaters when working on the fuel system of your vehicle. This will help you prevent a possible accident.