Isuzu 2008MY N Series Workshop Manual page 84

Step
1. Inspect the fuel system line connections
between the fuel tank and the fuel supply
pump for tightness and all fuel hoses for cuts,
cracks and for the use of proper clamps.
Notice: The fuel system from the fuel tank(s)
to the fuel supply pump is under a slight
vacuum with the engine running. As a result,
air can enter the fuel system if these
connections are not tight. Air in the fuel
system will
fluctuations especially at high engine speed
and load, which may set this DTC.
2. Pump the priming pump until it becomes firm.
If there is a leak on the suction side of the fuel
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system between the priming pump and the
fuel supply pump, the priming pump will not
build up sufficient firmness and fuel leakage
may occur.
3. Start the engine and check for high side fuel
system leaks at the fuel supply pump and fuel
rail.
Notice: Fuel may leak under the cylinder head
cover from the inlet high pressure line. In such
case, the engine oil level will rise. Inspect for
fuel leakage into the engine oil.
4. Repair any fuel system leaks as necessary.
Did you find and correct the condition?
1. Turn OFF the ignition.
2. Remove the rubber fuel hose from the fuel
filter housing (fuel supply pump side). Use a
pan to catch the fuel from the removed fuel
line.
Important: The fuel pressure/ vacuum gauge
connector and the adapter hose must be
cleaned before connecting to the fuel line.
Otherwise, foreign material internal to the
tools line may damage the fuel supply pump.
3. Connect the gauge adapter (5-8840-2844-0/
EN-47667) with fuel pressure/ vacuum gauge
assembly (5-8840-2844-0/ J-44638) in series
with the filter housing and the disconnected
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fuel hose. Ensure the service tool and fuel line
connections are tight.
4. Bleed the fuel system by priming the priming
pump until it becomes firm, then crank over
the engine for a maximum of 5 seconds.
Repeat as necessary until the engine starts.
5. Let the engine run at idle for at least 1 minute.
6. Monitor the fuel pressure/ vacuum gauge
while holding the engine speed higher than
2500 RPM for a minimum of 1 minute.
Does the fuel pressure/ vacuum gauge ever
indicate a larger vacuum than the specified
amount during the test?
Action
cause fuel rail pressure
Engine Control System (4HK1)
Value(s) Yes
—
Go to Step 17
5 inHg
Go to Step 9
1A-81
No
Go to Step 7
Go to Step 8