310T Engine and Fuel Systems 4

Question 1

Which diesel engine emission control system recirculates exhaust gases back into the intake to reduce NOx emissions?

Accepted Answer

Exhaust Gas Recirculation (EGR)

Answer

EGR reduces peak combustion temperatures by diluting the intake charge with inert exhaust gas, which lowers the formation of NOx.

Question 2

During a diesel injector balance rate test, one injector shows a significantly higher fuel delivery than the others. This indicates the injector is:

Accepted Answer

Delivering too much fuel, possibly stuck open or leaking

Answer

A high balance rate means the ECM is commanding more fuel to compensate, indicating the injector is delivering too little—not too much—fuel on its own.

Question 3

What causes diesel engine 'cavitation erosion' damage to cylinder liners?

Accepted Answer

Coolant pressure fluctuations causing vapor bubble collapse on the liner exterior

Answer

Cavitation erosion occurs when coolant pressure waves cause vapor bubbles to form and implode against the wet cylinder liner's outer surface.

Question 4

A technician is diagnosing a no-start condition on a diesel. Fuel pressure is correct but the engine will not start. What should be checked next?

Accepted Answer

Glow plug or grid heater operation

Answer

If fuel pressure is adequate and the engine won't start in cold or normal conditions, faulty glow plugs or a grid heater are a primary suspect for diesels.

Question 5

What is the function of the intake throttle valve (ITV) on a modern diesel engine equipped with EGR?

Accepted Answer

Creates intake manifold vacuum to draw EGR gases into the intake

Answer

The intake throttle valve partially restricts airflow to create a pressure differential that helps pull EGR gases into the intake manifold.

(310t) Truck and Coach Technician Certification Practice Test

(310t) Truck and Coach Technician Certification Practice Test

310T Engine and Fuel Systems 4