JLG 400S Service And Maintenance Manual page 213

Checks
Fuel System Checks
Ignition System Checks
Additional Check
3121671
Table 3-14. GM Engine Symptom Diagnosis
² Check for Rich or Lean symptom that causes the condition. Drive the vehicle at the speed of the complaint. Monitoring the oxygen sensors will
help identify the problem.
² Check the fuel pressure while the condition exists. Refer to LPG Fuel System Diagnosis.
² Verify proper fuel control solenoid operation.
² Verify that the LPG manual shut-off valve is fully open.
² Check the in-line fuel filter for restrictions.
² Check for the proper ignition output voltage using the spark tester J26792 or the equivalent.
² Verify that the spark plugs are correct for use with LPG (R42LTS)
² Check the spark plugs. Remove the plugs and inspect them for the following conditions:
- Wet plugs
- Cracks
- Wear
- Improper gap
- Burned electrodes
- Heavy deposits
- Check the Crankshaft Position (CKP) sensor.
² Check the ECM grounds for being clean, tight, and in their proper locations.
² Check the generator output voltage.
² Check the vacuum hoses for kinks or leaks.
² Check Transmission
SECTION 3 - CHASSIS & TURNTABLE
Action
3-155