Service Manual Owner's manual

SECTION 3 - CHASSIS & TURNTABLE
3-162 – JLG Lift – 3121139
Exhaust System Checks  Check the exhaust system for a possible restriction:
- Inspect the exhaust system for damaged or collapsed pipes
- Inspect the muffler for signs of heat distress or for possible internal failure.
 Check for possible plugged catalytic converter. Refer to Restricted Exhaust System Diagnosis or Exhaust System in
the GM Base Engine Service Manual
Additional Checks 
Cuts Out, Misses
DEFINITION: A surging or jerking that follows engine speed, usually more pronounced as the engine load increases which is not normally felt above 1500 RPM.
The exhaust has a steady spitting sound at idle, low speed, or hard acceleration for the fuel starvation that can cause the engine to cut-out.
Preliminary Checks  Refer to Important Preliminary Checks.
Ignition System Checks  Start the engine.
 Wet down the secondary ignition system with water from a spray bottle, and look/listen for arcing or misfiring as you
apply water.
 Check for proper ignition output voltage with spark tester J 26792.
 Check for a cylinder misfire.
 Verify that the spark plugs are correct for use with LPG (R42LTS)
 Remove the spark plugs in these cylinders and check for the following conditions:
 Insulation cracks
 Wear
 Improper gap
 Burned electrodes
 Heavy deposits
 Visually/Physically inspect the secondary ignition for the following:
 Ignition wires for arcing, cross-firing and proper routing
 Ignition coils for cracks or carbon tracking
Engine Mechanical Checks  Perform a cylinder compression check.
 Check the engine for the following:
- Improper valve t im ing
- Bent pu shrods
- Worn rocker ar ms
- Worn camshaft lobe s.
- Broken or we ak va lve spr ings.
 Check the intake and exhaust manifold passages for casting flash.
Fuel System Checks  Check the fuel system - plugged fuel filter, low fuel pressure, etc. Refer to LPG Fuel System Diagnosis.
 Check the condition of the wiring to the low pressure lock-off solenoid.
Additional Check Check for Electromagnetic Interference (EMI).
 EMI on the reference circuit can cause a missing condition.
 Monitoring the engine RPM with a scan tool can detect an EMI.
 A sudden increase in the RPM with little change in the actual engine RPM, indicates EMI is present.
 If the problem exists, check the routing of the secondary wires and the ground circuit.
Table 3-13. Symptom Diagnosis
Checks Action