Service Manual Instruction Manual

SECTION 3 - CHASSIS & TURNTABLE
3-92 – JLG Lift – 3121616
Table 3-10. LP Fuel System Diagnosis
STEP ACTION VALUE(S) YES NO
1 Were you referred to this procedure by a DTC d ia gn os ti c c har t ? - - Go to Step 3 G o t o S te p 2
2 Perform the On Board Diagnostic (OBD) System Check.
Are any DTCs present in the ECM?
- - Go to the
applicable DTC Table
Go to St ep 3
3 Verify that the LPG fuel tank has a minimum of 1/4 tank of fuel, that the manual valve is open
and the tank quick connect is fully engaged
Does the vehicle have fuel?
- - Go to Step 4 - -
4 1. Connect a water column gauge or a manometer to the secondary test port of the low pressure
regulator (LPR).
2. Start the engine and allow it to reach operating temperature.
Does the engine start and run?
- - Go to Step 5 Go to Step 8
5 With the engine idling, observe the pressure reading for the LPR secondary pressure.
Does the fuel pressure fluctuate rhythmically OUTSIDE the specified range?
-1.0" to
-2.0" w.c
G o to St ep 25 Go to St ep 6
6 1. Disconnect the EPR electrical connectors. NOTE: This action will cause a DTC to be set by the
ECM
2. With the engine idling observe the pressure reading on the secondary test port.
Is the fuel pressure WITHIN the specified range?
-1.0" to
-2.0" w.c
Go to Fuel Control System
Diagnosis
Go to St ep 7
7 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 damage or leak-
age.
3. Inspect any vacuum hoses for leaks
Was a problem found and corrected?
- - Go t o S te p 2 6 G o t o S tep 22
8 1. Connect a water column gauge or a manometer to the secondary test port of the low pressure
regulator (LPR).
2. Crank the engine and observe the pressure reading for the LPR secondary pressure.
D oe s t he fu el pre ss ur e i nd ic at e a va cu um is pre se nt ?
- - Go t o S te p 1 2 G o t o S tep 9
9 1. Remove Air induction hose to the mixer
2. Observe the air valve for movement while the engine is cranking. Note: Movement of the air
valve will be minimal at cranking speeds.
D oe s t he ai r va lv e m ove w hen th e eng ine is c ra nk ed ?
- - Go t o S te p 1 1 G o t o S tep 10
10 1. Inspect the air intake stream to the mixer assembly and the throttle body for vacuum leaks.
2. Inspect the vacuum hoses from the mixer for proper connection and condition.
Was a problem found and repaired?
- - Go t o S te p 2 6 G o t o S tep 24
11 Inspect the fuel hose connection between the LPR and the mixer assembly for damage or leak-
age.
Was a problem found and repaired?
- - Go t o S te p 2 6 G o t o S tep 12
12 1. Connect a 0-10 psi gauge to the primary test port of the low pressure regulator (LPR).
2. Crank the engine and observe the pressure reading for the LPR primary pressure.
Is the fuel pressure ABOVE the specified value?
1- 3 PS I G o t o S te p 2 2 G o t o S tep 13
13 1. Turn OFF the ignition.
2. Disconnect the LPL connector.
3. Install a test light between the pins of the LPL connector.
4. Crank the engine. The test light should illuminate.
Does the test light illuminate?
- - Go t o S te p 1 4 G o t o S tep 16
14 Using a DVOM, check the resistance of the low pressure lock-off (LPL).
Is the resistance within the specified range?
12W - 16W G o to St ep 15 Go to St ep 23