G420F(FE) Service Manual 265 Chapter 8. Basic Troubleshooting
Lack of Power, Slow to Respond / Poor High Speed Performance / Hesitation During
Acceleration
Engine delivers less than expected power. Little or no increase in speed when accelerator pedal is pushed
down part way. Momentary lack of response as the accelerator is pushed down. Can occur at all vehicle
speeds. Usually most severe when first trying to make vehicle move, as from a stop. May cause engine to stall.
PRELIMINARY CHECKS
Perform the visual checks as described at start of “ Basic Troubleshooting” chapter.
Drive vehicle; verify problem exists.
Remove air filter and check for dirt or other means of plugging. Replace if needed.
PROBABLE CAUSE CORRECTIVE ACTION
Fuel system malfunction
Check for restricted fuel filter.
Check fuel supply.
Check for LPG vapor from LPG liquid outlet valve on tank.
Check for contaminated fuel.
Check for clogged fuel filter and repair or replace as required. See Chapter 4
Fuel Filter replacement
Check for plugged fuel line and remove any obstruction from the fuel line:
• Close liquid fuel valve.
• Using caution, disconnect the fuel line (some propane may escape).
• Clear obstruction with compressed air.
• Re-connect fuel line.
• Slowly open liquid fuel valve and leak test.
Check for faulty vapor connection between pressure regulator/converter and
mixer:
• Verify that there are no holes in hose.
• Observe that clamps are tight.
• Look for kinked, pinched and/or collapsed hose.
Monitor pre-catalyst O2 with Service Tool.
Check for proper pressure regulator operation.
See Chapter 6 Test and Adjustments.
Check for proper air/fuel mixer operation.
Ignition system malfunction
Check spark advance for excessive retarded ignition timing. Use Service Tool.
Check secondary voltage using an oscilloscope or a spark tester to check for a
weak coil.
Check spark plug condition.
Check poor spark plug primary and secondary wire condition.
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