Service Manual Owner's manual

Table Of Contents
SECTION 3 - CHASSIS & TURNTABLE
3-166 – JLG Lift – 3121139
Engine Mechan ical Check Check the engine for th e f ol lowin g:
- Broken motor mou nts
- Impro pe r valve timing
- Low compression
- Bent pushrods
- Worn roc ke r arms
- Broken or weak valve springs
- Worn cam shaft lobes
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
- Cracks
- 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 3-13. Symptom Diagnosis
Checks Action