The electric fuel pump is attached to the fuel sending unit, located in the fuel tank.
See Figures 1 and 2
- Properly relieve the fuel system pressure.
- If necessary for access, remove the air cleaner assembly and plug the vacuum port(s).
- Disconnect the flexible fuel supply line, located in the engine compartment between the fuel filter and throttle body.
- Install a fuel pressure gauge, such as J-29658 or equivalent, inline in-line between the fuel filter and throttle body unit (between the steel line and flexible hose). If necessary use an adapter or Tee fitting in order to connect the gauge and complete the fuel circuit.
A Tee fitting may be fabricated for this purpose. Depending on the fuel pressure gauge, short lengths of steel tubing, appropriately sized flare nuts and a flare nut adapter may be used.
- If the engine will run, start the engine and allow it to run at normal idle speed. The fuel pressure should be 9-13 psi (62-90 kPa).
- If the engine does not run, turn the ignition ON , but do not attempt to start the engine. Listen for the fuel pump to run. Within 2 seconds of turning the ignition ON pressure should be 9-13 psi (62-90 kPa). If necessary, cycle the ignition OFF , then ON again, in order to build up system pressure.
- If the fuel pump did not run or system pressure did not reach specification, locate the fuel pump test connector. The test connector is usually found on the driver's side of the engine compartment (on or near the fender), with a single wire (usually red) leading from the relay to the connector. Using a jumper wire, apply battery voltage to the test connector in order to energize and run the fuel pump. The pump should run and produce fuel pressure of 9-13 psi (62-90 kPa). If the pump does not run, check the relay and fuel pump wiring.
- If the pump pressure was lower than specification, first check for a restricted fuel line or filter and replace, as necessary. If no restrictions can be found, restrict the fuel supply line between the pressure gauge and the TBI unit (a flexible hose may be temporarily clamped to produce the restriction), then apply voltage to the test connector again. If pressure is now above 13 psi (90 kPa), replace the faulty pressure regulator. If pressure remains below 9 psi (62 kPa), then the problem is located in the fuel tank (the fuel pump, coupling hose or inlet filter).
- If during Step 7, the pressure was higher than specification, disengage the injector connector, then disconnect the fuel return line flexible hose which connects the line from the throttle body to the tank line. Attach a 5 / 16 ID flex hose to the fuel line from the throttle body and place the other end into an approved gasoline container. Cycle the ignition in order to energize the fuel pump and watch system pressure. If pressure is still higher, check for restrictions in the throttle body return line. Repair or replace the line if restrictions are found or replace the faulty pressure regulator if no other causes of high pressure are identified. If fuel pressure is normal only with the flexible hose-to-fuel tank line out of the circuit, check that line for restrictions and repair or replace, as necessary.
- Once the test is completed, depressurize the fuel system and remove the gauge.
- Secure the fuel lines and check for leaks.
- If removed, install the air cleaner assembly.
REMOVAL & INSTALLATION
- Properly relieve the fuel system pressure.
- Connect the negative battery cable.
Be sure to keep a Class B (dry chemical) fire extinguisher nearby.
- Drain the fuel tank, then remove it from the vehicle. refer to the procedure found later in this section for details.
- Using the GM fuel gauge sending unit retaining cam tool No. J-24187, J-36608 (or equivalent) or a brass drift and a hammer, remove the cam locking ring (fuel sending unit) by twisting counterclockwise. With the locking ring released, carefully lift the sending unit from the fuel tank.
Remove the fuel pump from the fuel sending unit, by performing the following procedures:
- Pull the fuel pump up into the mounting tube, while pulling outward (away) from the bottom support.
When removing the fuel pump from the sending unit, be careful not to damage the rubber insulator and the strainer.
- When the pump assembly is clear of the bottom support, pull it out of the rubber connector.
- Inspect the fuel pump hose and bottom sound insulator for signs of deterioration, then replace, as necessary.
- Push the fuel pump onto the sending tube.
- Using a new sending unit-to-fuel tank O-ring, carefully lower the sending unit/fuel pump assembly into the fuel tank.
When installing the sending unit, be careful not to fold or twist the fuel strainer or it may restrict the fuel flow.
- Secure the sending unit by turning or driving the lockring clockwise and into position under the tabs.
- Install the fuel tank assembly to the vehicle.
- Connect the negative battery cable and check for proper pump operation.