Ford Crown Victoria/Grand Marquis 1989-1998

General Information


All vehicles with the 4.6L and 5.0L engines are equipped with a Sequential Electronic Fuel Injection (SEFI) system. In this system, fuel is metered into each intake port in sequence with the engine firing order, according to engine demand, through fuel injectors mounted on a tuned intake manifold.

The SEFI system consists of two subsystems, the fuel delivery system and the electronic control system. The fuel delivery system supplies fuel to the fuel injectors at a specified pressure. The electronic control system regulates the flow of fuel from the injectors into the engine.

The fuel delivery system consists of an electric fuel pump, fuel filters, fuel supply manifold (fuel rail), fuel pressure regulator and fuel injectors. The electric fuel pump, mounted in the fuel tank, draws fuel through a filter screen attached to the fuel pump/sending unit assembly. Fuel is pumped through a frame mounted fuel filter, to the engine compartment, and into the fuel supply manifold. The fuel supply manifold supplies fuel directly to the injectors. A constant fuel pressure to the injectors is maintained by the fuel pressure regulator. The fuel pressure regulator is mounted on the fuel supply manifold, downstream from the fuel injectors. The excess fuel supplied by the fuel pump but not required by the engine, passes through the regulator and returns to the fuel tank through the fuel return line. The fuel injectors spray a metered quantity of fuel into the intake air stream when they are energized. The quantity of fuel is determined by the electronic control system.

Air entering the engine is monitored by speed, pressure and temperature sensors. The outputs of these sensors are processed by the Powertrain Control Module (PCM). The PCM computes the required fuel flow rate and determines the needed injector pulse width (injector "on" time) and sends a signal to the injector to meter the exact quantity of fuel. Each fuel injector is energized once every other crankshaft revolution, in sequence with the ignition firing order.

For description and testing of electronic control system components, see Emission Controls .

See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Fuel injection system and related components-5.0L engine


Safety is the most important factor when performing not only fuel system maintenance, but any type of maintenance. Failure to conduct maintenance and repairs in a safe manner may result in serious personal injury or death. Work on a vehicle's fuel system components can be accomplished safely and effectively by adhering to the following rules and guidelines.

To avoid the possibility of fire and personal injury, always disconnect the negative battery cable unless the repair or test procedure requires that battery voltage by applied.
Always relieve the fuel system pressure prior to detaching any fuel system component (injector, fuel rail, pressure regulator, etc.) fitting or fuel line connection. Exercise extreme caution whenever relieving fuel system pressure to avoid exposing skin, face and eyes to fuel spray. Please be advised that fuel under pressure may penetrate the skin or any part of the body that it contacts.
Always place a shop towel or cloth around the fitting or connection prior to loosening to absorb any excess fuel due to spillage. Ensure that all fuel spillage is quickly remove from engine surfaces. Ensure that all fuel-soaked cloths or towels are deposited into a flame-proof waste container with a lid.
Always keep a dry chemical (Class B) fire extinguisher near the work area.
Do not allow fuel spray or fuel vapors to come into contact with a spark or open flame.
Always use a second wrench when loosening or tightening fuel line connections fittings. This will prevent unnecessary stress and torsion to fuel piping. Always follow the proper torque specifications.
Always replace worn fuel fitting O-rings with new ones. Do not substitute fuel hose where rigid pipe is installed.