19FUEL SYSTEM
8
DESCRIPTION AND OPERATION
EGR FUEL SYSTEM COMPONENT LOCATION, (when fitted)
1.EGR modulator valve
2.Electrical harness plug
3.Vacuum spill pipe, modulator to air cleaner hose
4.Vacuum pipe, brake servo hose to modulator
valve
5.'T' piece connector
6.Vacuum pipe, vacuum pump to brake servo7.EGR valve
8.Vacuum pipe, modulator valve to EGR valve
9.Multi-plug connector, EGR valve
10.EGR control unit (fixed on base of centre seat or
cubby box)
11.EGR throttle position sensor
19FUEL SYSTEM
10
DESCRIPTION AND OPERATION Under varying engine speed and load condition the
control unit sends a signal to open the vacuum
modulator which allows a vacuum to be applied above
the EGR diaphragm. The vacuum supply is taken from
a 'T' connector in the brake servo hose. This process
is controlled by an engine speed/load map stored in
the EGR control unit memory.
Engine speed is measured by monitoring the
waveform present on one phase of the generator.
Throttle position is measured via a sensor mounted on
the fuel injection pump throttle lever. Closed loop
control is achieved by allowing the control unit (ECU)
to continually monitor EGR valve lift via the sensor
mounted on the valve; this valve lift is compared with
the actual valve lift required on the control unit map
and adjusted, if necessary.
With coolant temperature between 20°C and 100°C,
the engine having just returned to idle, EGR will shut
off after 25-30 seconds idling.
