Jeep Cherokee 2000 Service Manual - page 1229
FUEL SHUTDOWN SOLENOID
DESCRIPTION
The fuel shutdown solenoid is controlled and
operated by the ECM.
The fuel shutdown (shut-off) solenoid is used to
electrically shut off the diesel fuel supply to the high-
pressure
fuel
injection
pump.
The
solenoid
is
mounted to the rear of the injection pump.
The solenoid controls starting and stopping of the
engine regardless of the position of the accelerator
pedal. When the ignition (key) switch is OFF, the
solenoid is shut off and fuel flow is not allowed to the
fuel injection pump. When the key is placed in the
ON or START positions, fuel supply is allowed at the
injection pump.
FUEL INJECTION PUMP
DESCRIPTION
The fuel injection pump is a mechanical distribu-
tor–type, Bosch VP36 series (Fig. 3). A gear on the
end of the injection pump shaft meshes with the
drive gear at the front of engine. The pump is
mechanically timed to the engine. The ECM regu-
lates the timing of the injection pump.
The injection pump contains the fuel shutdown
solenoid, fuel temperature sensor, control sleeve sen-
sor, fuel quantity actuator and the fuel timing sole-
noid (Fig. 3).
In the electronically controlled injection pump, the
pump plunger works the same as the pump plunger
in a mechanically controlled injection pump, but the
amount of fuel and the time the fuel is injected is
controlled by the vehicle’s ECM, instead of by a
mechanical governor assembly. A solenoid controlled
by the ECM is used in place of the mechanical gov-
ernor assembly, and it moves a control sleeve inside
the pump that regulates the amount of fuel being
injected. There is no mechanical connection between
the accelerator pedal and the electronically controlled
injection pump. Instead, a sensor connected to the
accelerator pedal sends a signal to the ECM that rep-
resents the actual position of the accelerator pedal.
The ECM uses this input, along with input from
other sensors to move the control sleeve to deliver
the appropriate amount of fuel. This system is known
as “Drive-By-Wire”
The actual time that the fuel is delivered is very
important to the diesel combustion process. The ECM
monitors outputs from the engine speed sensor (fly-
wheel position in degrees), and the fuel injector sen-
sor (mechanical movement within the #1 cylinder
fuel injector). Outputs from the Accelerator Pedal
Position sensor, engine speed sensor (engine rpm)
and engine coolant temperature sensor are also used.
The ECM will then compare its set values to these
outputs to electrically adjust the fuel timing (amount
of advance) within the injection pump. This is
referred to as “Closed Loop” operation. The ECM
monitors fuel timing by comparing its set value to
when the injector #1 opens. If the value is greater
than a preset value a fault will be set.
Fig. 2 Fuel Filter/Water Separator Location
Fig. 3 Fuel Injection Pump
1 – FUEL INJECTION PUMP ASSEMBLY
2 – FUEL RETURN LINE
3 – FUEL SUPPLY LINE
4 – FUEL INJECTION PUMP 10–WAY CONNECTOR
5 – TIMING SOLENOID
6 – OVERFLOW VALVE
XJ
FUEL SYSTEM—2.5L DIESEL ENGINE
14 - 3
DESCRIPTION AND OPERATION (Continued)