FUEL SYSTEM
9
DESCRIPTION AND OPERATION OPERATION
Diesel engines operate by compression ignition. The
rapid compression of air in the cylinder during the
compression cycle heats the air and when fuel is
injected into the heated air, it ignites instantaneously.
During cold tarting, automatically controlled heater
plugs assist in raising the temperature of the
compressed air to ignition point.
A cold start advance unit advances the injection timing
to further assist starting. Idle quality is improved by
the high idle setting.
The engine is supplied with pre-compressed air by a
single stage turbocharger.
Exhaust gases passing over a turbine cause it to
rotate, driving a compressor mounted on the turbine
shaft. Air drawn from the cold air intake passes, via
the air cleaner, to the turbocharger where it is
compressed. Compression in the turbocharger warms
up the air considerably, so that it expands. As a result
the air mass per cylinder is reduced, having a
negative effect on power output. By fitting a charge-air
intercooler, located on the LH side of the radiator, the
air is cooled before reaching the cylinders. This
increases power output through increased mass of
oxygen in the combustion process, as well as
maximising engine durability, through maintaining
lower piston and head temperatures.
Fuel is drawn from the tank by a mechanical lift pump
and passes to the injection pump via a filter. In
addition to removing particle contamination from the
fuel, the filter incorporates a water separator, which
removes and stores water.
The sedimentor/s, when fitted, is located adjacent to
the fuel tank/s and separates contamination and water
particles in the fuel before reaching the fuel lift pump.
The injection pump meters a precisely timed, exact
quantity of fuel to the injectors in response to throttle
variations, injection timing varying with engine speed.
Any excess fuel delivered to the injection pump is
passed back to the tank via the spill return line.
Fuel is injected in a finely atomised form into the main
combustion chamber, the burning fuel expands
rapidly, creating extreme turbulence which mixes the
burning fuel thoroughly with the compressed air,
providing complete combustion.Cold Starting is assisted by heater plugs, a cold start
advance unit and a high idle setting.
Heater plugs
Heater plug operation is controlled by a timer unit,
start relay and resistor. When the ignition is turned on
the timer unit is energised, the heater plugs start to
operate and a warning light on the dashboard
illuminates, remaining on until the heater plugs are
automatically switched off.
The length of time the heater plugs will operate is
dependent on under bonnet temperature, which is
monitored by a sensor located in the timer unit.
Starting the engine results in the power supply to the
heater plugs passing through the resistor, which
reduces their operating temperature. The heater plugs
are cut out either by the temperature sensor in the
timer, or by a microswitch on the injection pump which
operates when the throttle is depressed.
Cold start advance
The cold start advance unit is connected to the engine
cooling system via hoses. It contains a temperature
sensitive element which is retracted when cold and
pulls the advance lever, via cable, towards the rear of
the pump against spring pressure. As coolant
temperature rises, the cold start element expands
releasing tension on the cable and allowing spring
pressure to move the advance lever forwards.
Exhaust gas recirculation (EGR), when fitted
Operation of the EGR system is dependent on the
following:
·Engine temperature - must be between 20°C and
100°C approx.
·Engine speed - must be between 630 and 2850
rev/min.
·Engine load - calculated by throttle position
sensor.
·EGR valve lift position.
·Duration of engine idling.
19FUEL SYSTEM
4
ADJUSTMENT TURBOCHARGER BOOST PRESSURE - CHECK
Service repair no - 19.42.06
1.Disconnect actuator hose from turbocharger and
insert a suitable 'T' piece connector.
2.Connect a short length of suitable hose to
turbocharger and 'T'piece.
3.Connect further hose to 'T' piece and pressure
gaugeLRT-12-011. The pressure gauge hose
must be long enough to reach into the vehicle
cab so that the gauge can be observed by driver
or passenger.
4.To check maximum boost pressure, drive
vehicle normally, but in such a manner that full
throttle can be maintained whilst climbing a hill
with engine speed held steady between 2,500
and 3,000 rev/min. Under these circumstances
boost pressure should read 0,95 - 1,09 Kgf/cm
2
(13.5 - 15.5 lb/in2).PRIMING THE FUEL SYSTEM
Service repair no - 19.50.01
NOTE: If the fuel system has been
completely drained carry out the
procedures for priming both the
sedimentor, if fitted, and fuel filter and injection
pump.
Sedimentor and fuel filter
If the sedimentor or fuel filter have been dismantled
and air has entered the fuel system carry out the
following procedure:
1.Slacken fuel filter bleed screw.
2.Operate hand priming lever on fuel lift pump until
fuel, free from air, emerges from filter.
NOTE: Ensure that the fuel pump lever is
on the bottom of operating cam when
priming, otherwise maximum movement of
the lever cannot be achieved.
3.Tighten filter bleed screw whilst fuel is still
emerging.
FUEL SYSTEM
1
REPAIR FUEL INJECTION PUMP
Service repair no - 19.30.07
Remove
1.Disconnect battery.
2.Disconnect and remove high pressure fuel
injection pipes, pump to injectors.
3.Viewing valve mechanism through oil filler cap
aperture, turn crankshaft clockwise until No. 1
cylinder is just before TDC.
4.Remove blanking plug from flywheel housing
and fit timing toolLRT-12-044, locating centre
pin on flywheel.
NOTE: A chassis undertray may be fitted
on some vehicle derivatives to conform to
legal requirements. When under chassis
adjustments or remove and refit procedures are
required, it may be necessary to remove the
undertray and/or integral access panels
See
CHASSIS AND BODY, Repair, Front undertray
or
See CHASSIS AND BODY, Repair, Rear undertray
5.Carefully rotate crankshaft clockwise until centre
pin engages with timing slot in flywheel.
6.Remove injection pump access plate, complete
with gasket, from front cover plate.
7.Fit pin fromLRT-12-045to injection pump gear.
8.Restrain pulley nut to prevent straining timing
belt and remove drive gear to pump hub fixing
bolts and retaining plate.
9.Remove pin from pump gear.
10.Fit gear retaining toolLRT-12-045with an 8 mm
washer, 1,5 - 2 mm thick, under each bolt head
in addition to the existing washer.
11.Remove throttle cable and hand throttle cable, if
fitted.
12.Disconnect lead from fuel cut-off solenoid, and
EGR throttle position sensor multi-plug, if fitted.
FUEL SYSTEM
3
REPAIR FUEL INJECTORS
Service repair no - 19.60.10
Remove
NOTE: When a fuel injector is considered
to be the cause of irregular running and
loss of power it will be necessary to fit a
donor set of injectors to determine which injector
is at fault. DO NOT attempt to dismantle or carry
out spray tests on the fuel injectors. This work
can only carried out by authorised Bosch dealers.
1.Remove oil filler cap and release sound
insulation cover from top of engine.
2.Disconnect high pressure fuel supply pipes from
injectors and injection pump. Remove in pairs.
3.Disconnect spill return hose(s) from injectors.
4.Plug pipes and injector connections to prevent
the ingress of dirt and foriegn matter.5.Remove retaining nut and release each injector
clamp plate from cylinder head.
6.Remove injector and discard copper washer.
Refit
7.Ensure injectors and seating in cylinder head are
clean.
8.Lightly grease a new copper sealing washer and
position on each injector.
9.Fit injectors in cylinder head with spill return
outlets facing outward.
10.Secure injector with clamp plate and nut. Tighten
nut to
25 Nm (18 lbf/ft).
NOTE: The clamp plates are slightly
curved and should be fitted with the
convex side uppermost.
11.Fit the spill return pipe with a single copper
washer under the head of the banjo bolt and 2
copper washers fitted between the injector and
the banjo. Tighten banjo bolt to
10 Nm (7 lbf/ft).
12.Fit high pressure pipes to injectors and injection
pump. Tighten union nuts to
28 Nm (21 lbf/ft).
13.Fit sound insulation cover and oil filler cap.
19FUEL SYSTEM
4
REPAIR FUEL LIFT PUMP
Service repair no - 19.45.09
Remove
NOTE: Blank off pipe ends and
connections to prevent ingress of dirt.
1.Disconnect battery.
2.Remove high pressure fuel pipes, injection pump
to injectors.
3.Disconnect fuel inlet and outlet pipes from lift
pump.
4.Remove 2 bolts and withdraw lift pump and
gasket from cylinder block.
Refit
5.Clean mating faces of pump and cylinder block.
6.Fit lift pump to cylinder block with a new gasket,
ensure correct location of operating lever with
camshaft.
7.Secure with bolts. Tighten to
25 Nm (18 lbf/ft).
8.Connect inlet and outlet pipes using new nuts
and olives.
9.Refit injector pipes. Tighten union nuts to
28 Nm
(21 lbf/ft).
FUEL SEDIMENTOR
Service repair no - 19.25.01
Remove
1.Disconnect battery.
2.Disconnect inlet and outlet fuel pipes from
sedimentor.
3.Slacken drain tap and allow sedimentor to
completely drain.
4.Remove 2 bolts, washers and nuts and detach
sedimentor from chassis mounting bracket.
Refit
5.Secure sedimentor to chassis mounting with
fixing bolts.
6.Reconnect inlet and outlet fuel pipes to
sedimentor.
7.Slacken drain plug until diesel free from air
flows, then retighten plug.
8.Prime vehicle fuel system.
See Adjustment,
Priming the fuel system
9.Reconnect battery.
ELECTRICAL
3
DESCRIPTION AND OPERATION Door and bonnet switches
Perimetric protection for the vehicle is provided by
ECU inputs connected to the starter switch, bonnet
switch and door switches.
Ultrasonic sensor
The ultrasonic sensor operates by emitting an air
pressure carrier wave which is subsequently received
by the sensor as it bounces back from objects inside
the vehicle. Once armed, the alarm will sound if wave
is disturbed by a door opening, or if movement is
detected inside the vehicle.
When the volumetric sensor is activated it monitors
movement within the vehicle for 15 seconds before
detecting and responding to intrusions. If the sensor
detects movement it delays arming until a quiet period
has lapsed; if continuous movement is detected, the
alarm will not arm volumetrically.
NOTE: Interior protection will not operate
until 15 seconds after alarm is set.
The ultrasonic sensor is positioned in a different
location, according to vehicle type, as follows:
·90/110 Station Wagon - RH cantrail trim
·90/110 Pick-up - On headlining, between interior
lamp and rear view mirror
·130 Crewcab - On headlining above RH door
Alarm sounder
Two types of alarm sounder can be fitted, one with a
battery back-up facility and or without battery back-up,
both providing an audible warning whenever the alarm
is triggered. The vehicle horn will also operate if the
alarm sounds.
The alarm sounder is fitted to LH inner front wing in
the engine compartment.
NOTE: Disconnecting the battery on
vehicles fitted with the battery backed-up
facility will result in the alarm sounding, if
correct procedure has not been followed.Engine immobilisation warning light
The engine immobilisation warning light is located on
the instrument panel, and provides a visual indication
that the engine is immobilised.
Anti-theft alarm indicator light
The anti-theft alarm indicator light is located on the
instrument panel, between the fuel and coolant
temperature indicators, and provides a visual
indication of the alarm/ immobiliser status.