| INCONSISTENT ENGINE IDLE SPEED |
Fast idle screw contacting low step of cam at hot idle.
Incorrect throttle linkage adjust- ment to carburettor.
Binding or sticking throttle link- age or accelerator pedal.
Sticking carburettor throttle shaft.
Excessive looseness of throttle shaft in bores of throttle body.
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Improperly adjusted or defective carburettor dashpot.
Incorrectly installed throttle plates
Idle compensator malfunctioning (if so equipped).
Positive crankcase ventilation sys-tem malfunctioning.
Sticking fuel inlet needle.
|
| POOR ACCELERATION |
Poor acceleration complaints fall under one of three headings: the engine is sluggish on acceleration, the engine stalls when accelerated, or the engine hesitates or develops a flat |
spot when accelerated. Poor acceleration is caused by either an excessively lean or rich mixture on acceleration.
|
| A LEAN MIXTURE ON ACCELERATION |
Low fuel pump pressure.
Sticking fuel inlet needle.
Low fuel level or float setting.
Restriction in main fuel passage.
Air leak between the carburettor and the manifold caused by loose mounting bolts or defective gasket.
Air leak at the throttle shaft caused by a worn throttle shaft.
Accelerating pump diaphragm de- fective.
Incorrect accelerating pump stroke adjustment.
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Accelerating pump fuel inlet valve not seating on acceleration.
Restriction in the accelerating pump discharge passage.
Accelerating pump discharge ball check and/or weight not coming fully off its seat, or failing to seat properly on the reverse stroke of the pump dla--phragm.
Air leak at the accelerating pump cover caused by a defective gasket or warped pump cover.
Weak power valve spring. |
| A RICH MIXTURE ON ACCELERATION |
Excessive fuel pump pressure.
High fuel level or float setting.
Fuel inlet needle not seating properly or worn needle and/or seat.
Malfunctioning automatic choke.
Excessive dirty air cleaner.
lncorrect accelerating pump stroke adjustment.
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Power valve leakage.
Restricted air bleeds.
Worn or damaged main metering jet.
Accelerating pump ball check and/or weight not seating properly.
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| SURGING (CRUISING SPEEDS TO TOP SPEEDS) |
Clogged main jets.
Improper size main jets.
Low fuel level or float setting.
Low fuel pump pressure volume.
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Clogged filter screen.
Distributor vacuum passage clogged.
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| REDUCED TOP SPEED |
Float setting too high or too low.
Fuel pump pressure or volume too high or too low.
Improper size or obstructed main jets.
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Faulty choke operation.
Improper throttle linkage adjust-ment.
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