SkyTrak 6036 Service Manual - Manual (Page 198)

Engine: Cummins 4BT3.9
7.20 Model 6036 Legacy
7.8.3 Fuel Level Sender and Gauge
The fuel level sender and gauge assembly is described in
Section 9.15.14, “Fuel Level Indicator and Fuel Level
Sender.”
7.8.4 Fuel Lift Pump Inspection and Testing
1. Inspect the camshaft lever and return spring for
excessive wear.
2. Test the diaphragm, remove the fuel inlet line
(Fig. 7-20, 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.
Figure 7-20 Testing a Typical Fuel Lift Pump
a. Fuel Lift Pump Removal
1. Disconnect the negative (-) battery cable from the
battery.
2. Clean debris from around the lift pump (Fig. 7-20, 2).
3. Disconnect the fuel inlet line (Fig. 7-20, 1).
4. Remove the capscrews (Fig. 7-20, 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 (Fig. 7-20, 2) with a new gasket.
Install and torque the capscrews (5) to 18 lb/ft (24 Nm).
3. Connect the fuel line (Fig. 7-20, 1). Vent air from fuel
system. Refer to the appropriate owners/operators
manual.
4. Connect the negative (-) battery cable (Fig. 7-2, 1).
7.8.5 Fuel Filter
Refer to the appropriate owners/operators manual for the
proper procedure for removing and replacing the fuel filter
(Fig. 7-20, 4).
7.8.6 Venting Air from the Fuel System
Refer to the appropriate owners/operators manual for the
proper procedure for venting air from the fuel system.
7.8.7 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 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.
MT2530
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