3
23
Fuel system
Trouble Shooting Guide
Probable causes
Stop screw for the throttle not working ● ● ● ●
Fuel tank/hose Fuel fi lter blocked ● ● ● ● ● ● ●
The fuel hose blocked ● ● ● ● ● ● ●
Air in fuel ducts ● ● ● ● ● ● ●
Incorrect/poor fuel ● ● ●
Pump diaphragm Vacuum pulse leakage ● ●
Vacuum pulse duct blocked ● ●
Loose screw(s) on the pump cover ● ● ●
Faulty pump diaphragm ● ● ●
Flow bellows Flow bellows damaged ●
The needle valve faulty ● ● ● ● ● ●
Carburettor is not fi tted correctly ● ● ● ●
Faulty heat insulation seal ● ● ● ●
Needle valve’s lever Lever arm damaged ● ● ● ● ●
Lever arm too high ● ● ● ●
Lever arm too low ●
Lever arm does not work correctly ● ● ● ● ● ● ● ● ● ●
Needle valve’s spring The spring is deformed ● ● ●
The spring is not fi tted correctly ● ● ● ●
Control diaphragm Diaphragm is damaged ● ● ● ● ● ●
Faulty seal ● ● ● ●
Needle valve Valve jams ● ● ●
Valve worn ● ● ● ● ● ● ●
Foreign object in the valve guide ● ● ● ● ● ● ●
Diffi cult to start
Flooding, fuel leakage
Diffi cult to prime when starting
Engine does not idle
Idles too slowly
Idling does not stabilise
Stops when idling
Engine does not accelerate
Engine stops when decelerating
Poor acceleration capacity
Poor performance at high speed
Symptom Starting Low speed Acceleration/
Deceleration
High
speed
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