52143 Mercruiser SCREW, EXHAUST MANIFOLD TO CYLINDER HEAD (4 3/4")

Illustration 1 g06201711
(1) Fuel Priming Pump
(2) Dry-Well Temperature Sensor
(3) Fuel Transfer Pump
(4) Low-Pressure Relief Valve
(5) Fuel Temperature Sensor
(6) Secondary Fuel Filters
(7) Fuel Pressure Sensor (Unfiltered)
(8) Fuel Pressure Sensor (Filtered)
(9) Starting Priority Valve
(10) Low-pressure Fuel System Pressure Regulator
(11) Flow Control Valve
(12) High-Pressure Relief Valve
(13) High-Pressure Fuel Pressure Sensor
(14) High-Pressure Junction Block
(15) High-Pressure Fuel Pump
(16) Double-Walled High-Pressure Fuel Lines
(17) Injector Back-Pressure Regulator
(18) Low-Pressure Injector Cooling/Leakage Lines
(19) Fuel Injectors/Clamps
(20) Accumulator Quill with Integrated Flow Limiter
(21) Clean Fuel Module (CFM)
(22) Primary Fuel FiltersLow-Pressure Fuel System
Low-Pressure Fuel System Schematic
Illustration 2 g06427958
(1) Fuel Supply
(2) Clean Fuel Module (CFM) Pump
(3) CFM Outlet Pressure Sensor
(4) Primary Fuel Filters
(5) Electric Fuel Priming Pump
(6) Electric Fuel Priming Pump Bypass
(7) Fuel Transfer Pump (FTP) Inlet Pressure Sensor
(8) Fuel Transfer Pump
(9) FTP Pressure Relief Valve
(10) Fuel Pressure Sensor (Unfiltered)
(11) Secondary Fuel Filters
(12) Fuel Temperature Sensor
(13) Fuel Pressure Sensor (Filtered)
(14) Low-Pressure Fuel System Pressure Regulator
(15) Secondary Fuel Filter Manifold
(16) High-Pressure Pump (HPP) Supply
(17) Starting Priority Valve
(18) Injector Cooling Fuel Supply
(19) High-Pressure Fuel Pump
(20) Fuel injectors
(21) Injector Cooling Circuit Pressure Regulator
(22) High-Pressure Pump Fuel Cooling and Leakage Flow
(23) Mono-Block
(24) Double-Walled Return Line
(25) Return to Fuel Tank Line
(26) Fuel Cooler (if equipped)
(27) Fuel Tank Vent Cap
(28) Fuel TankThe basic function of the low-pressure fuel system is to provide fuel to the high-pressure fuel pump inlet at the:
Proper pressure
Proper temperature
Proper cleanliness LevelA fuel tank vent cap (27) is on fuel tank (28) to equalize air pressure. The fuel supply (1) is drawn from the fuel tank by the CFM (2) and then passes through the primary fuel filters (4).The CFM assembly contains an electric fuel transfer pump, a fuel manifold with a pump outlet pressure sensor (3), and the primary fuel filters. The fuel then passes through the electric fuel priming pump (5). The priming pump is used after service or if the equipment has not been used recently.When the fuel system has air trapped in the fuel filters, lines, and other fuel system components, the engine could experience difficulty starting. The electric fuel priming pump forces the air that is in the fuel system out through the injector cooling circuit and back to the tank.Priming is required after servicing the fuel system such as changing the fuel filter. Priming is also recommended when the engine has not been used recently. Refer to the Operation and Maintenance Manual, Fuel System – Priming for details on the priming procedure.The fuel is then drawn into the mechanical fuel transfer pump (8) that pressurizes the low-pressure fuel system from 550 kPa (80 psi) to 850 kPa (123 psi). The fuel transfer pump is equipped with a 950 kPa (138 psi) relief valve to prevent overpressure. The low-pressure fuel system pressure regulator is not part of the fuel transfer pump.The fuel flows through secondary fuel filters (11) and then is split by the secondary fuel filter manifold (15) to provide fuel to high-pressure pump (19) and injector cooling fuel supply circuit (18). Pressure sensors are at the inlet (unfiltered fuel pressure) (10) and outlet (fuel pressure) (13) of the secondary fuel filters to monitor filter condition. A fuel temperature sensor (12) measures the temperature of the fuel exiting the secondary filter.During an engine start, starting priority valve (17) prevents flow to the injector cooling flow portion of the low-pressure fuel system until 250 kPa (36 psi) is reached. This action ensures adequate fuel flow to the high-pressure pump at engine cranking speeds.The pressure is regulated by the low-pressure fuel system pressure regulator (14) and excess fuel flow is returned to the inlet of the fuel transfer pump.The injector cooling circuit pressure regulator (21) maintains the pressure in the cooling rails above 375 kPa (54 psi). After the fuel from the cooling circuit has cooled the injectors, the fuel returns to the mono-block (23). The fuel merges with the high-pressure pump leakage and cooling flow and returns to tank through the fuel cooler (26) (if equipped).Low-Pressure Fuel System Locations
Illustration 3 g06174641
(1) Injector Cooling Circuit Back-Pressure Regulator
Illustration 4 g06428043
(2) Filtered Fuel Pressure Sensor
(3) Unfiltered Fuel Pressure Sensor
(4) Starting Priority Valve
(5) Low-Pressure Fuel System Pressure Regulator
(6) Fuel Transfer Pump
(7) Fuel Transfer Pump Pressure Relief Valve
(8) Fuel Transfer Pump Inlet Pressure Sensor
(9) Fuel Temperature Sensor
(10) Secondary Fuel Filters
Illustration 5 g06199140
(11) Clean Fuel Module located behind the chassis fuel tank
Illustration 6 g06199138
Fuel priming pump location may vary on different machine applications.
(12) Fuel priming pump in chassisHigh-Pressure Fuel System
Illustration 7 g06185145
(1) Injector
(2) Accumulator-Quill Tu