The TBI system uses an electric fuel pump mounted in the fuel tank. The fuel pump used in this system is a positive displacement, roller vane immersible pump with a permanent magnet electric motor.
The fuel is drawn in through an in-tank filter unit (some models use a filter sock) and pushed through the electric motor to the outlet. The pump contains two check valves. One valve is used to relieve internal fuel pump pressure and regulate maximum pump output. The other check valve, located near the pump outlet, restricts fuel movement in either direction when the pump is not operational. Voltage to operate the pump is supplied through the Automatic Shutdown (ASD) relay.
REMOVAL & INSTALLATION
- Relieve the fuel pressure procedure as described previously in this section.
- Disconnect the negative battery cable.
- Remove the fuel tank from the truck.
- Remove the locking ring, then lift out the fuel pump module. Tag any lines for replacement.
- Remove the sending unit attaching screws from the mounting bracket located on the drain tube.
- Disconnect the wires from the sending unit, then remove the sending unit.
- Remove the drain tube from the mounting lug at the bottom of the reservoir.
- Remove the lower most coil of the drain tube from the mounting lugs on top of the reservoir. Be careful to avoid unsnapping the return line check valve cover from the bottom of the reservoir.
- Release the pump mounting bracket from the reservoir. Press the bracket with both thumbs toward the center of the reservoir.
- Remove the pump mounting bracket and rubber collar from the hose. Cut the hose clamp on the supply line and discard the clamp. Remove the pump/filter assembly. Pry the filter from the pump.
- Press a new filter onto the pump.
- Using a new clamp, attach the supply hose.
- Position the pump mounting bracket and rubber collar on the supply hose between the bulge in the hose and the pump.
- Position the pump in the reservoir so that the filter aligns with the cavity in the reservoir.
- Snap the pump bracket into the reservoir.
- Position the coil tube on the reservoir so that the drain tube aligns with the mounting lugs on the reservoir.
- Snap the lower most coil into the mounting lugs on top of the reservoir.
- Snap the drain tube into the lugs on the bottom of the reservoir.
- Connect the wires to the sending unit.
- Align the index tab on the level unit with the index hole in the mounting bracket.
- Install the level unit screws.
- Install the assembly in the tank.
The fuel system test port is located on the fuel rail in the engine bay.
- Remove the fuel intake hose from the throttle body and connect fuel system pressure testers C-3292, and C-4749, or equivalent, between the fuel filter hose and the throttle body.
- Start the engine and read the gauge. Pressure should be 14.5 psi (100 kPa).
Mopar® ATM tester C-4805 or equivalent can be used. With the ignition in RUN, depress the ATM button. This activates the fuel pump and pressurizes the system.
If the fuel pressure is below specifications:
- Install the tester between the fuel filter hose and the fuel line.
- Start the engine. If the pressure is now correct, replace the fuel filter. If no change is observed, gently squeeze the return hose. If the pressure increases, replace the pressure regulator. If no change is observed, the problem is either a plugged pump filter sock or a defective fuel pump.
If the pressure is above specifications:
- Remove the fuel return hose from the throttle body. Connect a substitute hose and place the other end of the hose in a clean container.
- Start the engine. If the pressure is now correct, check for a restricted fuel return line. If no change is observed, replace the fuel regulator.