Isuzu 2008MY N Series Workshop Manual page 78

Step
1. Turn OFF the ignition.
2. Place the transmission in Neutral and set the
parking brake.
3. Start the engine.
3 4. Accelerate the engine between idle and
W.O.T. (accelerator pedal full travel) many
times while observing the DTC Information
with a scan tool.
Does the DTC fail this ignition?
1. Turn OFF the ignition.
2. Wait 1 minute for the fuel pressure to bleed
down from the fuel rail.
3. Turn ON the ignition, with the engine OFF.
4
4. Observe the Fuel Rail Pressure (FRP) Sensor
parameter with the scan tool.
Does the scan tool indicate within the
specified value?
1. Start the engine.
2. Perform the Cylinder Balance Test with a scan
tool.
3. Command each injector OFF and verify an
5
engine speed change for each injector.
Is there an injector that does not change
engine speed when commanded OFF?
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
6
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?
Action
cause fuel rail pressure
Engine Control System (4HK1)
Value(s)
—
Go to Step 4
0.9 to 1.0 volt
Go to Step 5
—
Go to Step 15
—
Go to Step 17
Yes No
An intermittent
problem by foreign
material in the fuel
system is
suspected. Go to
Step 13
Go to Step 12
Go to Step 6
Go to Step 7
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