SkyTrak 8042 Service Manual - Manual (Page 395)

Engine: Cummins QSB4.5T
7B.28 Model 8042, 10042, 10054 Legacy Rev. 10/03
7B.8.3 Fuel Level Sender and Gauge
The fuel level sender and gauge assembly is described in
Section 9.14.15, “Fuel Level Indicator and Fuel Level
Sender.”
7B.8.4 Fuel Lift Pump Inspection and Testing
1. To test the diaphragm, remove the fuel inlet line (1)
from the fuel lift pump (2). Block the fuel inlet with a
finger and operate the hand plunger (3). A properly
operating pump will provide suction that will remain
until the finger is removed from the inlet.
a. Fuel Lift Pump Removal
1. Disconnect the negative (-) battery cables (6) from the
batteries.
2. Clean debris from around the fuel lift pump (2).
3. Disconnect the fuel inlet line (1).
4. Remove the capscrews (5), gasket and fuel lift
pump (2).
b. Cleaning and Drying
Clean the exterior of the pump with mineral spirits, and
blow dry with compressed air.
Note: Parts replacement is not practical. The fuel lift
pump is serviced as an entire assembly.
c. Fuel Lift Pump Installation
1. Clean the mounting surface on the cylinder block.
2. Install the fuel lift pump (2) with a new gasket. Install and
torque the capscrews (5) to 18 lb-ft (24 Nm).
3. Connect the fuel line (1). Vent air from fuel system.
Refer to appropriate Owners/Operators Manual.
4. Connect the negative (-) battery cables (6) to the
batteries.
7B.8.5 Fuel Filter
Refer to the appropriate Owners/Operators Manual for
your vehicle for the correct fuel filter (4) removal procedure.
7B.8.6 Venting Air from the Fuel System
Refer to the appropriate Owners/Operators Manual for
your vehicle for the correct fuel system venting procedure.
7B.8.7 Fuel Injectors
The engine uses Bosch 17-mm, closed nozzle, hole-type
injectors. The injectors have different part numbers for
different engine ratings. The last four digits of the Cummins
part number (stamped on the bottom portion of the
injector) identify the injector.
IMPORTANT: Use only the specified injector for the engine.
Damage to the engine can occur if incorrect injectors are
used.
During the injection cycle, high pressure from the
injection pump rises to the operating (or “pop”) pressure,
which causes the needle valve in the injector to lift. Fuel
is then injected into the cylinder. A shimmed spring is
used to force the needle valve closed as the injection
pressure drops below the pop pressure to seal off the
nozzle after injection.
Failure of the needle valve to lift and to close at the
correct time, or a needle valve that is stuck open, can
cause the engine to misfire and produce low power. Fuel
leaking from the open nozzle can cause a fuel knock,
poor performance, smoke, poor fuel economy and rough
running.
MH4660 1
2 3
4
5
MH4440
6