MTC Advanced Diagnostics & Troubleshooting 3

Question 1

A technician performing a cylinder leak-down test finds 35% leakage with air escaping into the crankcase. This MOST likely indicates:

Accepted Answer

Worn or broken piston rings

Answer

Air escaping into the crankcase during a leak-down test is the definitive indicator of ring sealing failure.

Question 2

On a two-stroke outboard, excessive carbon buildup on the power valves (YPVS/EXUP) typically causes:

Accepted Answer

Hesitation and power loss in the mid-to-high RPM range

Answer

Power valves modify exhaust port timing; carbon restriction prevents them from opening fully, killing mid-to-high RPM power.

Question 3

Which test is the BEST method to confirm a faulty marine alternator versus a faulty voltage regulator?

Accepted Answer

Perform a full-field bypass test on the alternator

Answer

A full-field bypass directly energizes the rotor, isolating the regulator; if output rises, the regulator is faulty, not the alternator stator.

Question 4

A marine diesel engine's raw-water pump impeller fails frequently and prematurely. After replacing the impeller twice, the BEST next diagnostic step is:

Accepted Answer

Inspect the raw-water strainer for blockage causing cavitation

Answer

A clogged strainer starves the impeller of water, causing cavitation-induced rapid wear or failure.

Question 5

A fuel injected marine engine fails to start after the vessel sat for two weeks. Live data shows injector pulse but fuel rail pressure drops to zero within 30 seconds of key-off. The MOST likely cause is:

Accepted Answer

A leaking fuel pressure regulator or check valve in the pump

Answer

Rapid pressure bleed-down after key-off indicates the check valve in the pump or the pressure regulator is not holding residual pressure.

(MTC) Marine Technician Certification Practice Test

(MTC) Marine Technician Certification Practice Test

MTC Advanced Diagnostics & Troubleshooting 3