DESCRIPTION & OPERATION
When ignition is turned on, EEC power relay is energized, closing its contacts. Power is provided to both fuel pump relay and timing device in EEC module. Fuel pump runs through contacts of fuel pump relay. If ignition is not turned on within one second, timing device in EEC module will create an open ground circuit.
Opening ground circuit of fuel pump relay de-energizes fuel pump. This circuit provides for pre-pressurization of fuel system. When ignition switch is turned to "START" position. EEC module operates fuel pump relay to provide fuel for starting engine while cranking.
If vehicle is involved in a collision, inertia switch will stop fuel flow. Engine will run until residual fuel is exhausted. If inertia switch has been tripped, switch must be reset before vehicle can be restarted.
Inertia switch location on Bronco II and Ranger is on floorboard to right of transmission hump. Aerostar inertia switch is located in the right kick panel. On "E" series, switch location is passenger's side cowl panel, forward of right front door. On Bronco and "F" series, switch location is on left kick panel, near emergency brake pedal.
To reset inertia switch, turn ignition off. Check for fuel leaks in engine compartment, fuel lines, and at tank. If no leaks are found, reset switch by depressing button on top of inertia switch. If gasoline fumes or liquid are present, DO NOT reset switch.
2.3L, 2.9L & 3.0L MPFI
The electric fuel pump system used on these Multi-Point Fuel Injection (MPFI) engines consists of: an in-tank high pressure fuel pump, and frame mounted fuel filter. The fuel pump assembly includes the sending unit and float. A pressure relief valve, mounted internally, protects against over-pressurization of system if fuel flow is restricted. A check valve, located at the pump outlet, maintains system pressure after the engine is shut off to reduce hot starting problems. The 2.9L fuel pump assembly has an integral reservoir.
4.9L, 5.0L, 5.8L & 7.5L MPFI
The electric fuel pump system used on these Multi-Point Fuel Injection (MPFI) engines consists of: a low pressure boost pump mounted in the fuel tank, a high pressure fuel pump and separate reservoir mounted on the frame rail. A pressure relief valve, mounted internally, protects against over-pressurization of system if fuel flow is restricted. The low pressure pump provides pressurized fuel to the inlet of the high pressure pump to reduce noise and hot fuel problems.
On dual tank models, a fuel tank selector valve is located in the fuel filter/reservoir mounted on the frame rail. This selector valve differs from the previous units by not being electrically activated. The valve is operated by pressure from the in-tank fuel pumps. When the tank selector switch is in the FRONT position, power from the fuel pump relay is directed to the front tank fuel pump. When the tank selector switch is moved to the REAR position, power from the fuel pump relay is directed to the rear tank fuel pump. Pressurized fuel from the fuel pump moves a diaphragm in the dual function reservoir which is connected to a sliding valve. The sliding valve allows fuel to be drawn from and returned to the correct fuel tank. This design relies on proper operation of the tank mounted low-pressure fuel pumps. (Scheme 283)
Scheme 283
DEPRESSURIZING FUEL SYSTEM
Note. Before disconnecting any fuel system component that may be under pressure, perform the following procedure.
Disconnect battery cable. Remove fuel tank cap. Remove cap from pressure relief valve located on fuel supply manifold and attach EFI Pressure Gauge (T80L-9974-B). Use pressure release button on gauge to bleed off pressure and fuel into an approved container.
Another method of depressurizing system is by disconnecting inertia switch and cranking engine for a minimum of 20 seconds.
DUAL FUNCTION RESERVOIR
| CAUTION | Fuel system is under pressure. Before removing any fuel lines, depressurize fuel system. See DEPRESSURIZING FUEL SYSTEM . |
- Remove all lines from reservoir, note position and routing of lines and avoid fuel spillage. Apply 3-5 PSI (20.7-34.5 kPa) of air pressure to return port (small diameter tube) on engine side of reservoir (only one set of 2 ports). If air is out of only one port on the other side of reservoir, go to step 3). If air is not out of only one port on the other side of reservoir, go to next step.
- Block pressure port (large diameter tube) on engine side of the reservoir. Apply 3-5 PSI (20.7-34.5 kPa) of air to either of the pressure ports on the fuel tank side of the reservoir. Remove air and apply to return tube on engine side of reservoir as in step 1). If the pressure is out of only one return port on the other side of the reservoir, go to next step. If the air pressure is not out of only one return port on the other side of the reservoir, replace reservoir.
- Block engine pressure port of reservoir. Apply 3-5 PSI (20.7-34.5 kPa) of air to one pressure port and the corresponding return port on the fuel tank side of the reservoir. If air pressure is out of return port on engine side of reservoir, go to next step. If air pressure is not out of the return port on the engine side of reservoir, change to opposite return port and repeat this step. If reservoir fails, replace reservoir.
- Remove air from pressure port tested previously and apply air to other set of ports on reservoir. If the air pressure is out of the return port on the engine side, go to next step. If the air pressure is not out of the return port on the engine side, check connection to return port. If connection is okay, replace reservoir.
- Remove any blockage installed in the reservoir. Apply pressure to the engine side pressure port and note which port is open on the fuel tank side of the reservoir. Attach a pressure gauge (0-110 in. H2O) to the closed pressure port. Block the open port on the tank side of the reservoir. If pressure is present on the gauge, replace reservoir. If pressure is not present, go to next step.
- Remove the pressure and gauge from selected port in step 5). Attach gauge to closed return port. Apply pressure to return port on engine side and block open return port. If there is pressure on the gauge, replace the reservoir. If there is not pressure on the gauge, go reservoir is okay.
HIGH PRESSURE FUEL PUMP
| CAUTION | Fuel system is under pressure. Before removing any fuel lines, depressurize fuel system. See DEPRESSURIZING FUEL SYSTEM . |
Scheme 284
- Check fuel tank(s) for adequate fuel supply. Check for fuel leaks at fittings and lines. Install jumper lead to fuel pump test terminal of VIP test connector. (Scheme 284) Use a test lead long enough to reach under vehicle. Install fuel pressure gauge. Turn ignition switch to the "RUN" position. Ground jumper lead and refer to «FUEL PUMP PRESSURE WITH ENGINE RUNNING»(/ford/econoline-e150/1987-1991/remont/testing-diagnostics/#electric-fuel-pump) table. If fuel pressure is within specification, go to step 5). If fuel pressure is not within specification, go to step 2). FUEL PUMP PRESSURE WITH ENGINE RUNNING Application Pressure 2.3L 30-45 psi 2.9L 30-45 psi 3.0L 30-45 psi 4.9L 45-60 psi 5.0L 30-45 psi 5.8L 30-45 psi 7.5L 30-45 psi
- If fuel pressure is low but greater than 3 psi (indicates pump is working), go to step 3). If not, go to step 4).
- Check fuel system for plugged fuel filter or restricted fuel lines. Check for low voltage at the fuel pump (voltage should be with.5 volt of battery voltage). Disconnect fuel return line. If fuel is returning, replace pressure regulator. If filters are clear, voltage correct and no fuel return, replace fuel pump.
- Ensure that battery voltage and ground are present at fuel pump connector. If circuits and voltages are correct, replace fuel pump.
- Disconnect grounded test lead and note fuel pressure. Fuel pressure should remain within 3 psi for 3 minutes after disconnecting test lead. If fuel pressure holds, go to step 7). If not, go to step 6).
- Inspect for fuel leaks. If no leaks are found, disconnect and plug fuel return line. Ground test lead and raise pressure to normal level. If fuel pressure now holds, replace pressure regulator. If not, replace fuel pump.
- Disconnect vacuum to fuel pressure regulator and start engine. Fuel pressure should be within specification of «FUEL PRESSURE WITH ENGINE RUNNING»(/ford/econoline-e150/1987-1991/remont/testing-diagnostics/#electric-fuel-pump) table. If fuel pressure is correct, go to step 9). If fuel pressure is not, go to step 8).
- If fuel pressure is low, check fuel filter, fuel pressure regulator adjustment, fuel line restrictions or voltage to fuel pump. If all systems are normal, replace fuel pump.
- With engine idling and fuel pressure regulator vacuum hose disconnected, measure fuel pressure. Accelerate rapidly and note fuel pressure. If fuel pressure drops more than 5 psi, repeat step 8). If fuel pressure does not drop, fuel system is operating correctly.
LOW PRESSURE IN-TANK FUEL PUMP
| CAUTION | Fuel system is under pressure. Before removing and fuel lines, depressurize fuel system. See DEPRESSURIZING FUEL SYSTEM . |
- Check fuel tank(s) for adequate fuel supply. Check for fuel leaks at fittings and lines. Install jumper lead to fuel pump test terminal of VIP test connector. (Scheme 284) Use a test lead long enough to reach under vehicle. Raise vehicle and ground test lead. Use a stethoscope and listen for pump operation. If low pressure pump is running, go to step 2). If not, go to step 3).
- Disconnect test lead from ground. Remove reservoir inlet hose at reservoir. Place fuel hose in one quart calibrated container and ground test lead for 5 seconds. Fuel level should be at least 6 ounces. If fuel pump volume is correct, fuel pump is okay. If not, restrict fuel line momentarily to prime pump. If no flow develops, check for blocked fuel lines. If no blockage is found, replace pump.
- If pump does not run, inspect all electrical connections. Check inertia switch and fuel pump relay for operation. If high pressure pump runs, but low pressure pump does not and voltage is present, replace low pressure fuel pump.
Removal & Installation (MPFI Frame-Mounted Fuel Pump)
Relieve fuel system pressure. See DEPRESSURIZING FUEL SYSTEM . Disconnect wiring at pump. Disconnect fuel lines. Unbolt 3 bolts attaching pump to frame. To install, reverse removal procedure. Start engine and check for leaks.
Removal & Installation (In-Tank Fuel Pump)
- Disconnect battery negative cable. Raise and support vehicle. Remove fuel tank. Turn sending unit lock ring counterclockwise and pull ring away from tank.
- Lift fuel pump/sending unit assembly from tank. Note position of alignment tabs (if used). To install, reverse removal procedure. Start engine and check for leaks.
