DESCRIPTION
Bosch electric fuel pumps are 12-volt, positive displacement roller cell type. Operating pressure is determined by one or more external fuel pressure regulators in the engine compartment. Fuel pumps include an external replaceable discharge check valve, to prevent fuel from returning to the tank when pump is turned off. Some pumps may also incorporate a damper chamber on the outlet, to prevent pulsations in the fuel lines.
Scheme 42
OPERATION
Fuel pumps are actuated by relays when ignition switch is in "START" or "RUN" position, and are protected from circuit overload by fuses and/or fusible links. Fuel is circulated through pump rotor and brushes to the fuel outlet. Pumps are not serviceable and should be replaced when not operating properly. For fuel pump test procedures, see BOSCH CIS-E SYSTEM article in this section.
Removal
- Fuel pressure must be relieved prior to any component removal. Carefully remove and plug fuel lines to prevent spillage. Disconnect electrical connections. WARNING: Do not allow smoking, open flame or sparks in area while servicing fuel system components. Disconnect battery ground terminal prior to removing pump.
- Remove mounting bolts and retain rubber insulating grommets for reinstallation. Rotate fuel pump as required to clear chassis and remove from vehicle.
Installation
- Be sure rubber grommets and insulation are installed correctly or noise and vibration will result.
- Hook all fuel lines and return lines to proper fittings, and be sure they are tight to avoid air and/or fuel leaks.
- Route fuel lines so they will not vibrate or rub against other body parts. Test system for leaks with engine running.
- Disconnect negative battery cable. Remove access cover in luggage compartment/trunk. Disconnect transfer pump connector. Label hoses for reassembly and disconnect hoses. WARNING: Do not allow smoking, open flame or sparks in area while servicing fuel system components. Disconnect battery ground terminal prior to removing pump.
- Loosen and remove lock ring on transfer pump/fuel level sending unit by turning counterclockwise. Lift assembly from fuel tank.
Inspection
Inspect and clean if necessary pickup strainer/filter. Inspect sealing gasket on top of tank and replace if necessary.
- Insert transfer pump/fuel level sending unit into tank. Ensure gasket is aligned with matching marks on unit and tank.
- Install lock ring and tighten by turning clockwise until snug. DO NOT overtighten. Using new hose clamps, install fuel lines in order removed. Reconnect transfer pump connector. Reinstall access cover and reconnect negative battery cable.
See also:
• BOSCH CIS-E SYSTEM