LEC Engine Performance & Diagnostics 2

Question 1

A locomotive's turbocharger is surging at low throttle settings. What is the most likely cause?

Accepted Answer

Compressor wheel contamination or worn bearings

Answer

Turbocharger surging at low throttle is typically caused by compressor wheel contamination, fouling, or worn bearings that disrupt proper airflow.

Question 2

When performing a cylinder cutout test, what indicates a cylinder is contributing normally to engine output?

Accepted Answer

Engine RPM drops noticeably when the cylinder is cut out

Answer

A significant RPM drop when a cylinder is cut out confirms that cylinder was producing power; no drop indicates a non-contributing cylinder.

Question 3

A locomotive engineer notices black smoke from the exhaust at full throttle. Which condition is LEAST likely to cause this?

Accepted Answer

Engine oil diluted with coolant

Answer

Coolant-diluted oil typically causes white or blue smoke, not black smoke; black smoke indicates incomplete combustion from excess fuel or insufficient air.

Question 4

What does a consistently high exhaust back pressure reading indicate on a diesel locomotive?

Accepted Answer

The exhaust system is partially blocked or restricted

Answer

High exhaust back pressure signals a restriction in the exhaust path, such as a clogged muffler, damaged piping, or collapsed exhaust components.

Question 5

During engine startup, a locomotive shows excessive oil consumption with blue exhaust smoke. The most probable cause is:

Accepted Answer

Worn piston rings or valve seals allowing oil into combustion chamber

Answer

Blue smoke indicates burning engine oil, most commonly caused by worn piston rings or valve stem seals that allow oil to enter the combustion chamber.

(LEC) Locomotive Engineer Certification Practice Test

(LEC) Locomotive Engineer Certification Practice Test

LEC Engine Performance & Diagnostics 2