Isuzu N-Series. Manual - part 698

6E-214    Engine Control System (4HK1) 

6

1.

Turn OFF the ignition.

2.

Check 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 cause fuel rail pressure fluctuations
especially at high engine speed and load, which
may set this DTC.

3.

Pump the priming pump on the fuel filter until it
becomes firm. If there is a leak on the suction
side of the fuel system between the priming
pump and the fuel supply pump, the priming
pump will not build up sufficient firmness and
fuel leakage may occur.

4.

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.

5.

Repair any fuel system leaks as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 7

7

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 leakage from the
removed fuel line.

Important:
The fuel vacuum pump / pressure 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 suction side fuel pressure /
vacuum 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
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?

5 inHg

Go to Step 9

Go to Step 8

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-215

8

1.

Fully clamp off a fuel hose as close to the fuel
tank as possible (this will draw vacuum on the
fuel system). You can also disconnect a fuel
line and plug it.

2.

Start the engine and turn the idle up control
knob to the highest position. (Full clockwise
direction. The idle speed is increased up to
1600 RPM.)

3.

Monitor the fuel pressure / vacuum gauge.

Notice:
Release the clamp or open the plug when the
gauge is likely to be more than 8 inHg during the
test.

Can a vacuum of at least the specified amount be
pulled on the fuel system?

8 inHg

Go to Step 11

Go to Step 10

9

1.

Inspect the fuel lines between the fuel supply
pump and fuel tank for being crushed or
kinked.

2.

Inspect for a plugged fuel tank vent hose.

3.

Inspect inside the fuel tank (if possible) for any
foreign material that may be getting drawn into
the fuel line pickup causing a blocked
condition.

4.

Repair as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 14

10

1.

Turn OFF the ignition.

2.

Check 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.

3.

Repair as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 12

11

1.

Turn OFF the ignition.

2.

Unclamp or unplug the fuel line from the
previous step and reconnect the fuel line (if
disconnected).

3.

Start the engine and allow it to run for at least
1 minute.

4.

Perform the Injector Balancing test with the
Tech 2.

5.

Command each injector OFF and verify an
engine speed change for each injector.

Is there an injector that does not change engine
speed when commanded OFF?

—

Go to Step 17

Go to Step 19

Step

Action

Value(s)

Yes

No

6E-216    Engine Control System (4HK1) 

12

1.

Turn OFF the ignition.

2.

Disconnect the FRP regulator harness
connector.

3.

Inspect for an intermittent, for poor
connections and corrosion at the harness
connector of the FRP regulator (pins 1 and 2
of E-116).

4.

Disconnect the engine control module (ECM)
harness connector.

5.

Inspect for an intermittent, for poor
connections and corrosion on each FRP
regulator circuit at the harness connector of
the ECM (pins 89, 97, 105 and 113 of E-111
connector).

6.

Test for high resistance on each FRP regulator
circuit.

7.

Repair the connection(s) or circuit(s) as
necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 18

13

1.

Turn OFF the ignition.

2.

Disconnect the FRP sensor harness
connector.

3.

Inspect for an intermittent, for poor
connections and corrosion at the harness
connector of the FRP sensor (pins 1, 2 and 3
of E-113 connector).

4.

Disconnect the ECM harness connector.

5.

Inspect for an intermittent, for poor
connections and corrosion on each FRP
sensor circuit at the harness connector of the
ECM (pins 82, 87, 90 and 101 of E-111
connector).

6.

Test for high resistance on each FRP circuit.

7.

Repair the connection(s) or circuit(s) as
necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 15

14

Replace the fuel filter cartridge. Refer to Fuel Filter
Cartridge Replacement in the Fuel System Section.

Did you complete the replacement?

—

Go to Step 20

—

15

Replace the FRP sensor. Refer to Fuel Rail
Pressure (FRP) Sensor Replacement in this
section.

Did you complete the replacement?

—

Go to Step 20

—

16

Important:
Replacement injector must be programmed.

Replace the appropriate injector that was leaking
fuel found at Step 3. Refer to Fuel Injector
Replacement / Fuel Injector ID Code Data
Programming in this section.

Did you complete the replacement?

—

Go to Step 20

—

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-217

17

Important:
Replacement injector must be programmed.

Replace the appropriate fuel injector that does not
change engine speed when commanded OFF.
Refer to Fuel Injector Replacement / Fuel Injector
ID Code Data Programming in this section.

Did you complete the replacement?

—

Go to Step 20

—

18

Important:
The fuel supply pump must be timed to the engine
and adjustment value must be learned to the ECM.

Notice:
Always replace the fuel filter cartridge when a fuel
supply pump is replaced.

Replace the fuel supply pump and fuel filter
cartridge. Refer to Fuel Supply Pump Replacement
in this section and Fuel Filter Cartridge
Replacement in Fuel System section.

Did you complete the replacement?

—

Go to Step 20

—

19

Notice:
There is a possibility that the pressure limiter valve
stuck open or opening pressure has fallen.

Replace the pressure limiter valve. Refer to Fuel
Rail Replacement in this section.

Did you complete the replacement?

—

Go to Step 20

—

20

1.

Reconnect all previously disconnected
harness connector(s).

2.

Clear the DTCs with the Tech 2.

3.

Turn OFF the ignition for 30 seconds.

4.

Start the engine.

5.

Operate the vehicle within the Conditions for
Running the DTC.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 21

21

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic 

Trouble Code (DTC) 

List

System OK

Step

Action

Value(s)

Yes

No