Isuzu N 2008 Series Workshop Manual page 78

Step
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.)
8
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?
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
9
foreign material that may be getting drawn into
the fuel line pickup causing a blocked
condition.
4. Repair or replace as necessary.
Did you find and correct the condition?
1. Inspect the fuel system line connections
between the fuel tank and the fuel supply
pump for tightness and all fuel hoses for cuts,
10 cracks and for the use of proper clamps.
2. Repair or replace as necessary.
Did you find and correct the condition?
1. Turn OFF the ignition.
2. Disconnect
connector.
3. Inspect for
connections and corrosion at the harness
connector of the FRP regulator (pins 1 and 2
of E17).
4. Disconnect the ECM harness connector.
11
5. Inspect for
connections and corrosion at the harness
connector of the ECM (pins 89, 97, 105 and
113 of E12).
6. Test for high resistance on each circuit.
7. Repair the connection(s) or circuit(s) as
necessary.
Did you find and correct the condition?
Action
the FRP regulator harness
an intermittent, for
an intermittent, for
Engine Control System (4JJ1)
Value(s)
8 inHg
—
—
poor
—
poor
Yes
Go to Step 11 Go to Step 10
Go to Step 17 Go to Step 13
Go to Step 17 Go to Step 11
Go to Step 17 Go to Step 16
1A-75
No