Service Manual

SECTION 3 - CHASSIS & TURNTABLE
3-120 – JLG Lift – 3121202
Engine Mechanical Check
² Ch eck the engin e for the f oll owing:
- Broken mot or mounts
- Imp roper valve timing
- Low co mpr ession
- Bent pushr ods
- Worn rocke r ar ms
- Broken o r weak valve spr ings
- Worn camsh af t l obe 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 do wn w ith no change in the
accelerator pedal.
Preliminary Checks Refer to Important Preliminary Checks.
Sensor Checks ² Check Heated Exhaust Gas Oxygen Sensor (HEGO) performance.
Fuel System Checks
² Check for Rich or Lean symptom that causes the condition. Drive the vehicle at the speed of the complaint. Moni-
toring 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.
Ignition System Checks
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
- Cr ack s
- Wea r
- Improper gap
- Burned electrodes
- Heavy deposits
- Check the Crankshaft Position (CKP) sensor.
Additional Check
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
Table 3-12. Symptom Diagnosis
Checks Action