Service Manual Manual

SECTION 3 - CHASSIS & TURNTABLE
3120788 – JLG Lift – 3-133
Engine Mec hanical Check  C heck the engi ne for the fol lowing:
- Broken motor mounts
- Improper v alve timing
- Low compress ion
- Bent pushro ds
- Worn r ocker arms
- Broken or weak valve springs
- Worn ca mshaft lobe s
Surges/Chuggles
DEFINITION: The engine has a power variation under a steady throttle or cruise. The vehicle feels as if it speeds up and slows down with no change in the accel-
erator pedal.
Preliminary Checks Refer to Important Preliminary Checks.
Sensor Checks  Check Heated Exhaust Gas Oxygen Sensor (HEGO) performance.
Fuel System Checks  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.
 Check the fuel pressure while the condition exists. Refer to LPG Fuel System Diagnosis.
 Verify proper fuel control solenoid operation.
 Verify that the LPG manual shut-off valve is fully open.
 Check the in-line fuel filter for restrictions.
Ignition System Checks  Check for the proper ignition output voltage using the spark tester J26792 or the equivalent.
 Verify that the spark plugs are correct for use with LPG (R42LTS)
 Check the spark plugs. Remove the plugs and inspect them for the following conditions:
- Wet plugs
- Crack s
- Wear
- Improper gap
- Burned electrodes
- Heavy deposits
- Check the Crankshaft Position (CKP) sensor.
Additional Check  Check the ECM grounds for being clean, tight, and in their proper locations.
 Check the generator output voltage.
 Check the vacuum hoses for kinks or leaks.
 Check Transmission
Table 3-12. Symptom Diagnosis
Checks Action