Lpf Fuel System Diagnosis - JLG 600SJ Service And Maintenance Manual

SECTION 3 - CHASSIS & TURNTABLE
STEP
1 Were you referred to this procedure by a DTC diagnostic chart?
Perform the On Board Diagnostic (OBD) System Check.
2
Are any DTCs present in the ECM?
Verify that the LPG fuel tank has a minimum of 1/4 tank of fuel, that the manual
3 valve is open and the tank quick connect is fully engaged
Does the vehicle have fuel?
1. Connect a water column gauge or a manometer to the secondary test port
of the low pressure regulator (LPR).
4
2. Start the engine and allow it to reach operating temperature.
Does the engine start and run?
With the engine idling, observe the pressure reading for the LPR secondary
5 pressure.
Does the fuel pressure fluctuate rhythmically OUTSIDE the specified range?
1. Disconnect the EPR electrical connectors. NOTE: This action will cause a
DTC to be set by the ECM
6 2. With the engine idling observe the pressure reading on the secondary test
port.
Is the fuel pressure WITHIN the specified range?
1. Inspect the air intake stream between the mixer assembly and the throttle
body for leaks.
2. Inspect the fuel hose connection between the LPR and mixer assembly for
7
damage or leakage.
3. Inspect any vacuum hoses for leaks
Was a problem found and corrected?
1. Connect a water column gauge or a manometer to the secondary test port
of the low pressure regulator (LPR).
8 2. Crank the engine and observe the pressure reading for the LPR secondary
pressure.
Does the fuel pressure indicate a vacuum is present?
1. Remove Air induction hose to the mixer
2. Observe the air valve for movement while the engine is cranking. Note:
9
Movement of the air valve will be minimal at cranking speeds.
Does the air valve move when the engine is cranked?
1. Inspect the air intake stream to the mixer assembly and the throttle body for
vacuum leaks.
10 2. Inspect the vacuum hoses from the mixer for proper connection and condi-
tion.
Was a problem found and repaired?
Inspect the fuel hose connection between the LPR and the mixer assembly for
11 damage or leakage.
Was a problem found and repaired?
1. Connect a 0-10 psi gauge to the primary test port of the low pressure regu-
lator (LPR).
12 2. Crank the engine and observe the pressure reading for the LPR primary
pressure.
Is the fuel pressure ABOVE the specified value?
3-110
Table 3-11. LPF Fuel System Diagnosis
ACTION
– JLG Lift –
VALUE(S) YES
- - Go to Step 3
Go to the
- -
applicable DTC Table
- - Go to Step 4
- - Go to Step 5
-1.0" to
Go to Step 25
-2.0" w.c
-1.0" to Go to Fuel Control
-2.0" w.c System Diagnosis
- - Go to Step 26
- - Go to Step 12
- - Go to Step 11
- - Go to Step 26
- - Go to Step 26
1- 3 PSI Go to Step 22
NO
Go to Step 2
Go to Step 3
- -
Go to Step 8
Go to Step 6
Go to Step 7
Go to Step 22
Go to Step 9
Go to Step 10
Go to Step 24
Go to Step 12
Go to Step 13
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