On the MFI system, since the fuel injectors injector the fuel into the intake manifold, the system needs to operate at a high pressure to inject the fuel at a good velocity and to help atomize the fuel charge as it enters the manifold. The fuel system pressure is extremely important for the function of the fuel injectors. The electric fuel pump provides more than enough pressure and the fuel pressure regulator has the job of bringing that fuel pressure down to a level that the injectors need and help to stabilize any surges the fuel pump might create.
REMOVAL & INSTALLATION
- Safely relieve the pressure within the fuel system-refer to the procedures described previously in this section.
- Disconnect the negative battery cable.
- Drain the engine coolant to a level below that of the intake manifold.
- Remove the air intake hose, the breather hose, the wiring harness connector,the air intake pipe and the air hose.
- Disconnect the accelerator and kickdown cables from the throttle body.
- Remove the water hose from the throttle body.
- Unplug the vacuum hose from the fuel pressure regulator.
- Remove the throttle body from the intake manifold plenum-refer to the procedures described previously in this section.
- Extract the gasket from the throttle body/intake manifold plenum mounting surface; a new gasket will be needed upon assembly.
- Remove the fuel return hose, the mounting bolt and the fuel pressure regulator from the fuel rail. The O-ring between the fuel rail and the fuel pressure regulator will need to be replaced with a new one upon assembly.
- Install a new O-ring on the fuel pressure regulator and coat it lightly with clean gasoline. Install and tighten the fuel pressure regulator to fuel rail mounting bolts to 5-8 ft. lbs. (7-11 Nm).
- Install the fuel rail mounting bolts through the fuel return hose mounting bracket, through the fuel rail and into the intake manifold. Tighten them to 6-9 ft. lbs. (8-12 Nm).
- Connect the fuel return hose to the fuel return rail. Fasten it in place with the spring clip.
- Connect the high pressure fuel line to the fuel rail, using as new O-ring. Coat the O-ring with a little gasoline to help it seal better. Tighten the two retaining bolts to 1-2 ft. lbs. (2-3 Nm) of torque.
- Plug the fuel injector harness back onto the fuel injectors.
- Install the throttle body back onto the intake manifold plenum with a new gasket. Make sure the gasket goes onto the intake manifold plenum to throttle body opening with the gasket projection up and to the left (look straight into the intake manifold plenum opening, in other words from the passenger-side of the engine compartment). Install the throttle body mounting bolts with 11-16 ft. lbs. (15-22 Nm) of torque.
- Connect the vacuum hose, the water hose, the automatic transmission kickdown cable (if so equipped) and the accelerator cable. Refer to the accelerator cable adjustment procedure described earlier in this section.
- Connect the air hose, the air intake pipe, the breather hose and the air intake hose.
- Plug the wiring harness connector back into the throttle body.
- Fill the engine coolant system back up.
- Connect the negative (-) battery cable back to the battery and start the engine. The engine may turn over a few times until the fuel system pressure can be brought back up to normal.
- Check for any coolant or fuel leaks, repair if necessary.
- Safely relieve the pressure within the fuel system.
- Disconnect the negative battery cable.
- Remove the air intake plenum, following procedures listed in Engine & Engine Rebuilding .
- Disconnect the fuel pressure regulator from the fuel rail and remove its O-ring. Disconnect the vacuum and fuel return hoses from the fuel pressure regulator.
- Replace the O-ring, coat it lightly with gasoline and install the fuel pressure regulator. Tighten the fasteners to 7 ft. lbs. (9 Nm).
- Connect the fuel return hose and any vacuum hoses.
- Reinstall the air intake plenum; refer to Engine & Engine Rebuilding in this guide for more in-depth directions on the installation or removal of the intake manifold plenum.
- Install the throttle body onto the intake manifold plenum; use the earlier described instructions in this section.
- Fill the coolant system back up to normal operating level.
- Connect the negative battery cable.
- Start the engine and check for fuel and coolant leaks; repair if needed.