JLG 450A_AJ Series II Service Manual - Manual (Page 183)

SECTION 3 - CHASSIS & TURNTABLE
3121180 – JLG Lift – 3-133
Table 3-14. LPF Fuel System Diagnosis
STEP ACTION VALUE(S) YES NO
1 Were you referred to this procedure by a DTC diagnostic chart? - - Go to Step 3 Go to Step 2
2 Perform On Board Diagnostic (OBD) System Check.
Are any DTCs present in the ECM? - - Go to the
applicable DTC Table
Go to Step 3
3 Verify LPG fuel tank has a minimum of 1/4 tank of fuel, manual valve is open and
tank quick connect is fully engaged
Does vehicle have fuel? - - Go to Step 4 - -
4 1. Connect a water column gauge or a manometer to Low Pressure Regulator
(LPR) secondary test port.
2. Start engine and allow it to reach operating temperature.
Does engine start and run? - - Go to Step 5 Go to Step 8
5 With engine idling, observe pressure reading for LPR secondary pressure.
Does fuel pressure fluctuate rhythmically OUTSIDE specified range? -1.0" to
-2.0" w.c
Go to Step 25 Go to Step 6
6 1. Disconnect EPR electrical connectors. NOTE: This action will cause a DTC to
be set by the ECM
2. With engine idling, observe pressure reading on secondary test port.
Is fuel pressure WITHIN specified range? -1.0" to
-2.0" w.c
Go to Fuel Control
System Diagnosis Go to Step 7
7 1. Inspect air intake stream between mixer assembly and throttle body for leaks.
2. Inspect fuel hose connection between LPR and mixer assembly for damage
or leakage.
3. Inspect vacuum hoses for leaks
Was a problem found and corrected? - - Go to Step 26 Go to Step 22
8 1. Connect a water column gauge or a manometer to LPR secondary test port.
2. Crank engine and observe pressure reading for LPR secondary pressure.
Does fuel pressure indicate a vacuum is present? - - Go to Step 12 Go to Step 9
9 1. Remove Air induction hose to mixer
2. Observe air valve for movement while engine is cranking. Note: Movement of
air valve will be minimal at cranking speeds.
Does air valve move when engine is cranked? - - Go to Step 11 Go to Step 10
10 1. Inspect air intake stream to mixer assembly and throttle body for vacuum
leaks.
2. Inspect vacuum hoses from mixer for proper connection and condition.
Was a problem found and repaired? - - Go to Step 26 Go to Step 24
11 Inspect fuel hose connection between LPR and mixer assembly for damage or
leakage.
Was a problem found and repaired? - - Go to Step 26 Go to Step 12
12 1. Connect a 0-10 psi gauge to primary test port of LPR.
2. Crank engine and observe pressure reading for LPR primary pressure.
Is fuel pressure ABOVE specified value? 1- 3 PSI Go to Step 22 Go to Step 13
13 1. Turn OFF ignition.
2. Disconnect LPL connector.
3. Install a test light between pins of LPL connector.
4. Crank engine. Test light should illuminate.
Does test light illuminate? - - Go to Step 14 Go to Step 16
14 Using a DVOM, check resistance of Low Pressure Lock-off (LPL).
Is resistance within specified range? 12W - 16W Go to Step 15 Go to Step 23