LEC Engine Performance & Diagnostics 3

Question 1

A diesel locomotive engine experiences a sudden drop in oil pressure while operating at Notch 8. The engineer should FIRST:

Accepted Answer

Immediately place throttle to idle and prepare to shut down

Answer

A sudden oil pressure drop is a critical emergency requiring immediate throttle reduction to idle and engine shutdown preparation to prevent severe engine damage.

Question 2

What is the purpose of the load regulator on an EMD diesel-electric locomotive?

Accepted Answer

To maintain constant engine RPM by adjusting generator excitation load

Answer

The load regulator controls generator excitation to match electrical load to engine capability, keeping engine RPM constant at each throttle notch.

Question 3

Which of the following best describes 'dynamic braking capacity' limits related to engine diagnostics?

Accepted Answer

Dynamic braking capacity is limited by traction motor cooling capacity and grid resistor temperature

Answer

Dynamic braking capacity is thermally limited by the ability of grid resistors and traction motors to dissipate the heat generated during braking.

Question 4

An engine overspeed trip activates during a downhill grade with dynamic brakes applied. What is the most likely cause?

Accepted Answer

The dynamic brake grids have failed open, removing the load from the engine

Answer

If dynamic brake grids fail open, the generator load is removed from the engine, which can accelerate to overspeed if throttle is not immediately reduced.

Question 5

Water in the fuel system of a diesel locomotive most commonly results in:

Accepted Answer

Injector tip corrosion, rough running, and potential injector failure

Answer

Water in diesel fuel causes injector corrosion, poor atomization, rough combustion, and can lead to catastrophic injector failure.

(LEC) Locomotive Engineer Certification Practice Test

(LEC) Locomotive Engineer Certification Practice Test

LEC Engine Performance & Diagnostics 3