899912023 Mercury TAPPET, (3.458)

Illustration 1 g01343672
Diagram of the basic fuel system (typical example)
(1) Electronic unit injector (EUI)
(2) Solenoid for the fuel injection pump
(3) Wastegate valve (if equipped)
(4) Secondary speed/timing sensor
(5) Electronic control module (ECM)
(6) Fuel injection pump
(7) Primary speed/timing sensor
(8) Intake manifold pressure sensor
(9) Fuel manifold pressure sensor
(10) Engine oil pressure sensor
(11) Intake manifold temperature sensor
(12) Coolant temperature sensor
(13) Diagnostic connector Low Pressure Fuel System
Illustration 2 g01362505
Low pressure fuel system (typical example)
(14) Fuel cooler (optional)
(15) ECM
(16) Fuel injection pump
(17) Fuel transfer pump
(18) Primary fuel filter
(19) Secondary fuel filter
(20) Water separator
(A) Outlet for high pressure fuel to the high pressure fuel manifold
(B) Return from the pressure relief valve on the high pressure fuel manifold
(C) Return to fuel tank
(D) Return from the electronic unit injectors
(E) Fuel in from the fuel tank Fuel is drawn from the fuel tank (E) through a 20 micron primary fuel filter (18) and the water separator (20) to the transfer pump (17). The transfer pump increases the fuel pressure to 400 to 500 kPa (58 to 72.52 psi). The fuel is pumped through the optional fuel cooler (14) to the ECM (15). The fuel cools the ECM. The fuel passes from the ECM to a 2 micron primary fuel filter (18). The fuel filter removes particulates from 20 microns to 2 microns in size in order to prevent contamination of the high pressure components in the fuel system. Fuel passes from the fuel filter to the fuel injection pump (16). The fuel is pumped at an increased pressure to the high pressure fuel manifold.Excess fuel from the high pressure fuel pump returns to the tank through a non-return valve. There is a small orifice in the fuel filter base in order to bleed any air back to the tank.The leak off fuel from the electronic unit injectors returns from a connection in the cylinder head to the pressure side of the transfer pump.High Pressure Fuel System
Illustration 3 g01343616
High pressure fuel system (typical example)
(21) Electronic unit injector
(22) High pressure fuel manifold
(23) Fuel pump gear
(24) Fuel injection pump
(25) Solenoid for the fuel injection pump
(26) Fuel transfer pump
(27) Fuel pressure relief valve
(28) Fuel pressure sensor The fuel injection pump (24) feeds fuel to the high pressure fuel manifold (22). The fuel is at a pressure of 70 MPa (10152.7 psi) to 130 MPa (18855 psi). A pressure sensor (28) in the high pressure fuel manifold (22) monitors the fuel pressure in the high pressure fuel manifold (22). The ECM controls a solenoid (5) in the fuel injection pump (24) in order to maintain the actual pressure in the high pressure fuel manifold (22) at the desired level. The high pressure fuel is continuously available at each injector. The ECM determines the correct time for activation of the correct electronic unit injector (21) which allows fuel to be injected into the cylinder. The leakoff fuel from each injector passes into a drilling which runs along the inside of the cylinder head. A line is connected to the rear of the cylinder head in order to return the leakoff fuel to the pressure side of the fuel transfer pump.Components of the Fuel Injection System
The fuel injection system has the following mechanical components:
Primary filter/water separator
Fuel priming pump
Secondary fuel filter
Fuel injection pump
Fuel injectors
Fuel manifold
Pressure relief valve
Fuel pressure sensor The following list contains examples of both service and repairs when you must prime the system:
A fuel filter is changed.
A fuel line is replaced.
The fuel injection pump is replaced.Primary Filter/Water Separator
The primary filter/water separator is located between the fuel tank and the priming pump.Fuel Priming Pump
Illustration 4 g01343617
Hand Fuel Priming Pump
The pump has a plunger (29) which is manually operated in order to prime the fuel system. Air is removed from the fuel system to the fuel return line to the tank. The fuel transfer pump is located in the fuel injection pump.
Illustration 5 g01343630
Electric Fuel Priming Pump
The electric fuel priming pump can be installed on some engines.Secondary Fuel Filter
Illustration 6 g01343642
Typical example
The secondary fuel filter (30) is located after the priming pump. The filter is always before the fuel injection pump.Fuel Pump Assembly
The fuel pump assembly consists of a low pressure transfer pump and a high pressure fuel injection pump. The pump assembly is driven from a gear in the front timing case at half engine speed. The fuel injection pump has two pistons that are driven by a camshaft. There is a cam for each piston and each cam has three lobes. The fuel injection pump delivers a volume of fuel six times for each revolution. The stroke of the pistons is fixed. The injector will use only part of the fuel that is delivered by each stroke of the pistons in the pump. The solenoid for the fuel injection pump is controlled by the ECM in order to maintain the fuel manifold pressure at the correct level. The solenoid allows excess fuel to be diverted away from the fuel manifold and back to the tank. A feature of the fuel injection pump allows fuel to return to the tank continuously.Fuel injection Pump