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14 - 2
FUEL SYSTEM
FUEL SYSTEM (Continued)
Fig. 1 Typical Test for Leaks with Cardboard
1 - HIGH-PRESSURE LINE
2 - CARDBOARD
3 - FITTING
DIAGNOSIS AND TESTING - AIR IN FUEL
SYSTEM
Air will enter the fuel system whenever fuel supply
lines, separator filters, injection pump, high-pressure
lines or injectors are removed or disconnected. Air
trapped in the fuel system can result in hard start-
ing, a rough running engine, engine misfire, low
power, excessive smoke and fuel knock.
Inspect the fuel system from the fuel tank to the
injectors for loose connections (Refer to 14 - FUEL
SYSTEM - WARNING). Leaking fuel is an indicator
of loose connections or defective seals. Air can also
enter the fuel system between the fuel tank and the
fuel pump. Inspect the fuel tank and fuel lines for
damage that might allow air into the system.
With the DRBIII connected to the vehicle, select
Engine and the select Sensor Display. Page down to
view Fuel Pressure Set Point and Actual Fuel Pres-
sure. Start the engine and observe the Fuel Pressure
Set Point and the Actual Fuel Pressure. If the Actual
Fuel Pressure Oscillates above and below the Fuel
Pressure Set Point in a regular cycle, perform the
Fuel System Air Purge procedure (Refer to 14 -
FUEL SYSTEM - STANDARD PROCEDURE).
If the Actual Fuel Pressure gradually drops below
the Fuel Pressure Set Point then spikes well above
the Fuel Pressure Set Point, replace the fuel pres-
sure solenoid (Refer to 14 - FUEL SYSTEM/FUEL
INJECTION/FUEL
REMOVAL), then perform the Fuel System Air Purge
PRESSURE
SOLENOID
procedure (Refer to 14 - FUEL SYSTEM - STAN-
DARD PROCEDURE).
STANDARD PROCEDURE
STANDARD PROCEDURES - CLEANING FUEL
SYSTEM COMPONENTS
CAUTION: Cleanliness cannot be overemphasized
when handling or replacing diesel fuel system com-
ponents. This especially includes the fuel injectors,
high-pressure fuel lines, fuel rail, and fuel injection
pump. Very tight tolerances are used with these
parts. Dirt contamination could cause rapid part
wear and possible plugging of fuel injector nozzle
tip holes. This in turn could lead to possible engine
misfire. Always wash/clean any fuel system compo-
nent thoroughly before disassembly and then air
dry. DO NOT wire brush injector nozzles when
cleaning. Cap or cover any open part after disas-
sembly. Before assembly, examine each part for
dirt, grease or other contaminants and clean if nec-
essary. When installing new parts, lubricate them
with clean engine oil or clean diesel fuel only.
STANDARD PROCEDURE - DISCONNECTING
AND CONNECTING FUEL LINES
NOTE: Capture and store any fuel spillage in appro-
priately marked containers.
(1) Disconnect negative battery cable.
(2) Push release arm to release position A, as far
as the stop (arrow) (Fig. 2).
(3) Disconnect fuel line.
(4) Immediately return the release arm back to the
assembly position, as far as the stop (Fig. 2).
The release arm must not be left in the release
position for a long time. Connectors left in the
release position for lengthy periods may leak and
must be replaced.
(5) Insert connector into connection in assembly
position (B) (Fig. 2).
(6) Ensure that the connectors are firmly seated
and free of leaks (Fig. 2).
STANDARD PROCEDURES - DRAINING WATER
FROM FUEL FILTER
Refer to Fuel Filter/Water Separator removal/in-
stallation for procedures (Refer to 14 - FUEL SYS-
TEM/FUEL DELIVERY/FUEL FILTER / WATER
SEPARATOR - REMOVAL).
-
VA
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