G420E/G424E Tier LP Engine Basic Troubleshooting 42
Problem Probable Cause Corrective Action
Incorrect Idle speed control
Incorrect timing or spark control
See Chapter 5 Advanced Diagnostics &
Chapter 9 Tests and Adjustments
Rough Idle
Engine Mechanical See Engine Manufacturers Service Manual
Incorrect Idle speed control
Throttle sticking
See Chapter 5 Advanced Diagnostics &
Chapter 9 Tests and Adjustments
High Idle Speed
Acceleration Pedal sticking or
incorrect pedal signal
Check pedal return spring travel for binding
z See Chapter 5 Advanced Diagnostics
Clogged fuel filter Repair/replace as required
z See Chapter 3 Fuel Filter replacement
Plugged fuel line Remove obstruction from the fuel line
z Close liquid fuel valve
z Using caution, disconnect the fuel line
(some propane may escape)
z Clear obstruction with compressed air
z Re-connect fuel line
z Slowly open liquid fuel valve & Leak test
Air filter clogged Check air filter
z Clean/replace as required
Faulty vapor connection between
the pressure regulator/converter
and the mixer
Check connection
z Verify no holes in hose
z Clamps must be tight
z Look for kinked, pinched and/or
collapsed hose
Pressure regulator malfunction Test pressure regulator operation
z See Chapter 9 Tests and Adjustments
Air/Fuel Mixer malfunction Check mixer
z See Chapter 8 Air/Fuel mixer section
Restricted exhaust system Check exhaust system
z Measure exhaust back pressure
Incorrect ignition control
Incorrect air/fuel control
Poor High Speed
Performance
Incorrect throttle position
See Chapter 5 Advanced Diagnostics &
Chapter 9 Tests and Adjustments
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