Description - Mercury MerCruiser D2.8L D-Tronic Service Manual

INJECTION PUMP

Description

Mercury MerCruiser EDI Diesel Engines use the Bosch, Type VE, Distributor Fuel Injection
Pump with an electronic governor and integral timing device.
The pump is mounted on the port side of the engine and is driven by the camshaft gear. The
pump is formed basically by an electrical (upper) part and a mechanical (lower) part. The
mechanical (lower) part is mainly the same as the previous mechanically controlled VE-style
pump, with the exception of the electric Timing Solenoid Valve that is controlling pressure
between the upper and lower chambers (parts) of the pump.
When the ECM (Engine Control Module) signals the Timing Solenoid Valve it is
electro-mechanically held open (pressure reduction) and the start of injection is retarded.
When the valve is fully closed (pressure increase) the start of injection is advanced. In the
intermediate range, the ON/OFF ratio (duty cycle) can be infinitely varied by the ECM allowing
for a wide range of control over the injected fuel quantity. This is especially so when
simultaneously the ECM is controlling the upper electrical portion of the pump.
The upper electrical part consists of these main components:
•
Fuel Quantity Actuator
•
Fuel Quantity Sensor
•
Fuel Temperature Sensor
•
Fuel Shut Off Valve
The ECM uses inputs from various sensors to make decisions on the quantity of fuel and
amount of pump timing advance or retard allowed. During engine operation, the ECM
calculates the fuel flow rate based on signals from the Throttle Position sensor and Engine
rpm speed sensor. This information is then sent to the injection pump, which regulates the
rate of the fuel flowing into the cylinders of the engine. The injection pump uses a rotational
electromagnetic actuator, called the Fuel Quantity Actuator (or control collar actuator), to
move the delivery plunger which controls the pumps working stroke and the amount of fuel
flow.
Fuel quantity adjustments are made based on internally stored information after a
comparison is made between the nominal position on the fuel pump's control collar with the
actual position of the control collar. Further adjustment of the fuel quantity actuator can be
made based on such inputs as fuel temperature detected by the Fuel Temperature Sensor
in the pump. These adjustments will be made until the actual position of the fuel quantity
actuator (control collar) coincides with its nominal position. The adjusted fuel quantity is then
electronically timed to deliver the correct pressurized amount of fuel to the fuel injectors.
Injection pump pressure, at the fuel injectors, exceeds 27000 kPa (3900 psi).
Diesel engines are stopped by shutting off the fuel supply. This is accomplished by the Fuel
Quantity Actuator delivering no (zero) fuel or by an ECM controlled redundant electric Fuel Shut
Off Valve on the pump.
Page 5D-6
SERVICE MANUAL NUMBER 22
90-860074--1 FEBRUARY 2002