CIRCUIT OPERATION
DEFENDER 90 NAS
3
STARTING - OPERATION
When the ignition switch is in position 'II', power flows across the switch to fuse 20 of the
passenger compartment fuse box (C581-13) on the white wire. Fuse 20 (C581-20) is
connected to the fuel pump relay winding in the ECM relay module (C154-2) by the
white/green wire. The fuel pump relay winding (C154-1) is grounded through the ECM
(C634-24) on the blue/purple wire. The ECM grounds the fuel pump relay winding for a
short time when the ignition is switched to position 'II', and continuously during cranking
and while the engine in running. With the fuel pump relay winding energized, the fuel
pump relay closes and power from fuse 6 (C575-2) of the engine compartment fuse box
flows through the fuel pump relay (C157-7) on the purple/white wire. The fuel pump relay
(C157-4) is connected to the inertia switch (C123-3) by the white/purple wire. Assuming
the inertia switch is closed, power flows across the switch (C123-1) to the fuel pump
(C113-4) on the white/purple wire. The fuel pump is grounded on a black wire.
Turning the ignition switch to the crank position 'III', allows power to flow across the
switch (C90-1) to the starter relay winding (C151-85) on the white/red wire. The starter
relay winding is grounded on the black/yellow wire to the starter inhibitor/reverse switch
(C69-5). With the gear selector lever in park or neutral, the route to ground is from the
inhibitor switch (C69-4) to the immobilization unit (C57-10) on the black/orange wire.
Assuming the engine has been mobilized, the immobilization unit is grounded on a black
wire. With the starter relay energized, power from fusible link 5 of the engine
compartment fuse box (C570-2) flows across the relay (C151-87) on the brown wire.
The starter relay is connected to the starter motor solenoid (C179-1) by the brown/red
wire. The starter motor solenoid is grounded through the starter motor fixing. With the
starter motor solenoid energized, feed from the battery is connected to the starter motor
(C178-1) through the starter solenoid on a red wire.