CARBURETTOR – Air – DGCA Question Bank For Politics

#1. The pressure in the induction manifold of a normally aspirated engine:

Remains constant as the throttle is opened.

Decreases as the throttle is opened.

Initially increases as the throttle is opened but decreases after approximately the half open position.

Increases as the throttle is opened.

#2. The purpose of an accelerator pump is to:

Assist in the atomisation of the fuel before it leaves the discharge nozzle.

Prevent a rich cut when the throttle lever is advanced rapidly.

Prevent dissociation and detonation.

Prevent a weak cut when the throttle lever is advanced rapidly.

#3. The fuel flow to a piston engine will vary according to:

The R.P.M. and the throttle position only.

The R.P.M. the throttle position and the mixture setting.

The R.P.M. and the mixture setting only.

The R.P.M. only.

#4. The primary function of a diffuser in a carburettor is to:

Control the mixture strength over part of the engine speed range.

Vent air from the float chamber.

Emulsify the fuel during engine acceleration.

Enable adjustment of the engine slow running speed.

#5. The venturi in the carburettor choke tube creates:

A positive pressure over the discharge nozzle.

A depression over the fuel discharge nozzle.

A positive pressure at the throttle valve.

A decrease in the velocity of the air entering the engine.

#6. The fuel priming pump supplies fuel directly to:

The throttle butterfly valve.

The exhaust manifold.

The induction manifold.

The inside of the combustion chamber in the region of the spark plug.

#7. A weak mixture would be indicated by:

A drop in engine speed.

White smoke in the exhaust manifold.

Detonation and black smoke from the exhaust.

An increase in engine speed with black smoke from the exhaust.

#8. The presence of an engine driven fuel pump on an engine fitted with a carburettor:

Dispenses with the need for a carburettor float chamber.

Ensures a positive flow of fuel to the discharge nozzles.

Ensures a positive flow of fuel to the carburettor float chamber.

Dispenses with the need for a fuel priming system.

#9. It would normally be considered dangerous to pump the throttle lever when starting an engine because:

It could increase the risk of fire in the carburettor air intake.

It would prevent the engine starting.

The engine would start too rapidly.

It would richen the mixture to the point where spontaneous combustion would occur in the combustion chamber.

#10. A typical air/fuel ratio for normal engine operation would be:

15 parts of air to one of fuel by weight.

20 parts of air to one of fuel by volume.

15 parts of air to one of fuel by volume.

12 parts of air to one of fuel by weight.

#11. Excessive cylinder head temperatures are caused by:

The prolonged use of weak mixtures.

The ignition timing being too far advanced.

The prolonged use of rich mixtures.

The ignition being too far retarded.

#12. The mixture supplied by the carburettor to the engine is said to be weak when:

The proportion of air in the mixture is insufficient to allow full combustion of the fuel.

The proportion of air in the mixture is greater than that needed for full combustion of the fuel.

A grade of fuel lower than that specified for the engine is used.

There is insufficient power in the engine for take off.

#13. In an attempt to maintain the correct air/fuel ration while climbing into the decreased density air of higher altitude:

The valve timing can be changed.

An accelerator pump can be fitted.

A mixture control is used.

A diffuser is fitted.

#14. The greater the weight of combustible mixture in the cylinders:

The weaker is the mixture.

The more the power decreases.

The lower the cylinder head temperature will be.

The greater the power developed by the engine.

#15. A rich mixture is supplied to the cylinders at take off and climb:

To give greater thermal efficiency.

To cool the charge temperature and prevent detonation.

To increase the volumetric efficiency.

To give excess power.

#16. A fuel stainer should be fitted:

In the inlet manifold.

At the air intake.

Before the main jet.

After the main jet.

#17. The correct air/fuel ratio for an engine running at idle is:

Weak.

Chemically correct.

16:1

Rich

#18. The method of priming an engine not fitted with a priming pump is to:

Activate the mixture control lever several times.

Turn the engine over several times on the starter motor before selecting the ignition on.

Pump the throttle several times.

Position the throttle lever midway between open and close.

#19. A possible cause of the engine backfiring could be:

An exhaust valve sticking open.

A broken push rod.

A blocked float chamber.

A sticking inlet valve.

#20. An overly rich mixture at slow running could be caused by:

The priming pump being left open.

Low fuel pressure.

The float chamber level being too low.

A partially blocked main jet.

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