Lpf fuel system diagnosis -94 – JLG 450A_AJ Series II Service Manual User Manual
Page 134
SECTION 3 - CHASSIS & TURNTABLE
3-94
– JLG Lift –
3121290
Table 3-12. 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 LPR secondary pressure reading.
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 secondary test port pressure reading.
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 pres-
sure.
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 condi-
tion.
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 pres-
sure.
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