Fuel Pump - Electric Ford Bronco II I

COMPONENT TESTING

Note. Specific component testing information not available. Refer to any tests performed during REMOVAL & INSTALLATION or OVERHAUL procedures

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 activated, switch must be reset before vehicle can be restarted.

Inertia switch location on Aerostar (2.3L), Bronco II, "F" series and Ranger is on floor board to right of transmission hump. Switch is located in engine compartment on Aerostar (3.0L). On "E" series, switch location is passenger's side cowl panel, forward of right front door.

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.

A high pressure, frame-mounted pump is used on vehicles with EFI equipped engines. This pump can supply up to 15.9 gals. (60L) of fuel per hour at 39 psi (2.7 kg/cm 2 ). A pressure relief valve, mounted internally, protects against over-pressurization of system if fuel flow is restricted.

A low pressure electric in-tank fuel pump is used to provide pressurized fuel to inlet of high pressure pump, reducing pump noise and pump overheating problems.

Vehicles with 7.5L engines use a submerged, in-tank fuel pump. Pump is designed to prevent loss of fuel flow during off-road use.

2.3L Turbo Diesel uses a frame mounted electric fuel boost pump which introduces fuel to system. Fuel, under boost pump pressure, flows through fuel filter conditioner. Conditioner is located between boost pump and fuel injection pump. When fuel conditioner has reached its capacity for trapping water, sensor turns on an instrument panel mounted indicator light.

For information on operation and testing of fuel selector valves, see ELECTRIC FUEL SELECTOR VALVES article in ACCESSORIES & EQUIPMENT section.

Note. Testing information for 2.3L Diesel boost pump is not available from manufacturer.

MPFI Models

1. Check fuel tank(s) for adequate fuel supply. Check for fuel leaks at fittings and lines. Locate electrical connector on frame-mounted fuel pump. With ignition off, disconnect fuel pump connector from harness and connect ohmmeter across body connector.
2. If continuity is 5 ohms or less, go to step 4. If continuity is more than 5 ohms, check for continuity between connector ground lead and ground. If no continuity exists, repair open in pump ground circuit and repeat step 2. If continuity exists, check for continuity between connector Pink/Black wire and ground.
3. If no continuity exists, check wiring at fuel pump/sending unit. If continuity exists, check continuity across pump terminals. If continuity exists, go to step 4. If no continuity exists, replace fuel pump/sending unit. Ensure fuel pump/sending unit connections are okay.
4. Turn ignition on. Using voltmeter, check for voltage between connector and ground. Voltage should be 12 volts for one second, then drop to zero volts. If voltage is incorrect, check wiring and repair as necessary. If voltage is correct, go to step 5.
5. Turn ignition off. Using ohmmeter, check for continuity across pump leads. If continuity exists, perform «FUEL PUMP PRESSURE TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#fuel-pump-electric) . If no continuity exists, check continuity at pump terminals. If still no continuity, replace frame-mounted fuel pump.

7.5L Engine

1. Check for adequate fuel supply. Check for fuel leakage from lines and fittings. Replace lines and/or fitting as necessary.
2. Remove fuel pump cut-off relay connector. Check for voltage between Yellow wire at connector and ground. If 12 volts are present, go to next step. If voltage is not present, check inertia switch and wiring. Reset switch (if necessary).
3. Connect voltmeter between Pink/Black wire of connector and ground. Crank engine momentarily, and note voltage reading. If 10-12 volts are present while cranking, go to step 4. If voltage is less than 10 volts, check fusible link and resistance wire.
4. With ignition off, check continuity between Pink/Black wire and ground. If continuity exists, go to step 5. If continuity does not exist, check tank selector relay (if equipped). If relay is okay, or is not used, go to step 5.
5. Check continuity across fuel pump terminals and wiring harness. If continuity exists, go to step 6. If continuity does not exist, replace fuel pump/sending unit assembly.
6. Attach relay connector. Connect voltmeter leads between Pink/Black wire and ground. Crank engine until oil pressure is built up, turn ignition back to "RUN" position, and note voltmeter reading.
7. If voltage (10-12 volts) remains steady, perform «FUEL PUMP PRESSURE TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#fuel-pump-electric) . If voltage (10-12 volts) is not steady, or never existed, check relay circuit and oil pressure switch.

MPFI Equipped Models

1. Using new Relay (E3EB-9345-BA, CA, DA or E3TF-9345-AA), drill a 1/8" hole in-line with pins, and as close to pins as possible. Part of relay skirt may be cut away to provide easier access to pins.
2. Solder a 16-18 gauge jumper wire between pins "2" and "4". (Scheme 13) Feed end of a long (8-10 foot), insulated, flexible wire through hole drilled in relay skirt, and solder end to exposed base of pin No. "1" (as close to relay base as possible). This will permit full insertion of relay into socket. Solder an alligator clip to other end of long flexible wire.

Modifying Fuel Pump Cut-Off Relay Solder long wire as close to relay base as possible. Courtesy of Ford Motor Co. Scheme 13

Scheme 14

1. With assistant in vehicle, raise vehicle on hoist. Locate fuel diagnostic valve. If diagnostic valve is present, go to step 2. If pump does not have diagnostic valve, fabricate test line and fitting assembly. (Scheme 15)
2. On 2.3L engine, relieve fuel system pressure by removing fuel tank cap. Disconnect vacuum hose from fuel pressure regulator located on engine fuel rail. Using a hand-held vacuum pump, apply 25 in. Hg to pressure regulator. Fuel pressure will be released through fuel return hose.
3. On all other EFI equipped models, relieve fuel system pressure by disconnecting fuel pump relay and cranking engine for at least 20 seconds. On all models, attach Gauge (T80L-9974-A) to diagnostic valve (or test line and fitting assembly). Turn ignition on and check pressure reading. (Scheme 14): Test Line & Fitting Assembly Apply pipe sealant to fittings. Courtesy of Ford Motor Co.
4. Reading should be 30-40 psi (2.1-2.8 kg/cm 2 ), if pump is operating properly and other system components are okay. Disconnect fuel return line at fuel rail. Avoid spilling fuel. Route hose from fuel rail fitting to a calibrated container of at least one quart capacity.
5. Replace fuel pump relay with modified relay. See «MODIFYING FUEL CUT-OFF RELAY»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#fuel-pump-electric). Ground wire coming from relay to a convenient ground point. Pump should now operate. Run fuel pump for 10 seconds.
6. Observe fuel flow volume and pressure. Fuel pump is operating properly if fuel pressure is 35-45 psi (2.5-3.2 kg/cm 2 ), fuel flow is a minimum of 5.6 oz. (166 ml), and fuel pressure remains at a minimum of 30 psi (2.1 kg/cm 2 ) immediately after pump stops.
7. If all 3 conditions are met, fuel pump is operating normally. If conditions are not met, check for engine and electrical problems.
8. If fuel pressure is okay, but fuel flow is less than specification, check for blocked filter(s), fuel supply lines and/or tank selector valve malfunction. After correcting any blockages, repeat test. If fuel flow is still incorrect, replace pump.
9. If both fuel pressure and fuel flow are correct, but system will not stay pressurized after pump is turned off, check for leaking injectors or regulator. If both are okay, replace fuel pump. If no fuel flow or fuel pressure is observed, fuel system should be checked as in step 8. If system is okay, replace fuel pump.

MPFI Models (In-Tank Fuel Pump)

1. Open fuel line at high pressure pump inlet. Connect hose to line from fuel tank. Route hose to a calibrated container of at least one quart capacity. Disconnect high pressure fuel pump electrical connector from body wiring harness.
2. Replace fuel pump relay with modified relay. See «MODIFYING FUEL CUT-OFF RELAY»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#fuel-pump-electric) . Ground wire coming from relay to a convenient ground point to energize fuel pump and measure flow for 10 seconds. NOTE: It may be necessary to momentarily block fuel hose to prime low pressure pump with outlet open and no back pressure on outlet. This is normal.
3. If fuel pump produces a minimum flow of 16 oz. (473 ml) of fuel, within 10 seconds, pump is operating correctly. If there is no flow from pump, check electrical circuit and check inlet for restrictions. If electrical circuits are okay and inlet is not restricted, replace pump.

7.5L Engine (In-Tank Fuel Pump)

1. Disconnect fuel line just before vapor separator. Route end of hose to a calibrated container of at least one quart capacity. Turn ignition on, but DO NOT crank engine. Jumper (short circuit) oil pressure switch terminals. Run fuel pump for 10 seconds. NOTE: To initate fuel flow, it may be necessary to momentarily block the hose to create a back pressure condition.
2. If fuel pump produces a minimum flow of 16 oz. (473 ml) of fuel within 10 seconds, pump is operating correctly. If there is no flow from pump, check fuel lines for blockage.
3. Check selector valve for proper operation (if equipped). Ensure spare tire does not pinch inlet line of fuel pump. If all 3 conditions are okay, replace fuel pump/sending unit assembly.

MPFI Frame-Mounted Fuel Pump

1. On 2.3L engine relieve fuel system pressure by removing fuel tank cap. Disconnect vacuum hose from fuel pressure regulator located on engine fuel rail. Using a hand-held vacuum pump, apply 25 in. Hg vacuum to pressure regulator. Fuel pressure will be released through fuel return hose.
2. On all other EFI equipped models, relieve fuel system pressure by opening electrical circuit to fuel pump and cranking engine for at least 20 seconds. On all models, 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)

1. Disconnect battery negative cable. Raise and support vehicle. Remove fuel tank. Turn sending unit lock ring counterclockwise and pull ring away from tank.
2. Lift fuel pump/sending unit assembly from tank. (Scheme 16) Note position of alignment tabs (if used). To install, reverse removal procedure. Start engine and check for leaks.

Electric Fuel Pump/Sending Unit Assembly Assembly shown is for vehicles with 7.5L engines. All other models are similar. Courtesy of Ford Motor Co. Scheme 15

SPECIFICATIONS

Note. Specifications not available. Refer to specifications within appropriate REMOVAL & INSTALLATION or TESTING subject in this article.

Scheme 16

Scheme 17

Scheme 18

See also:
• FUEL PUMP PRESSURE TEST