CEM Technical Skills & Application 3

Question 1

A motor grader blade drifts down during transport even though the hydraulic system pressure is within specification. What is the MOST probable cause?

Accepted Answer

Internal leakage past the blade lift cylinder piston seals

Answer

Internal bypass past worn piston seals allows fluid to transfer between cylinder chambers, causing slow drift under load even when system pressure is normal.

Question 2

Which diesel engine component is responsible for controlling injection timing in a common-rail fuel system?

Accepted Answer

Engine control module (ECM) commanding injector solenoids or piezo actuators

Answer

In common-rail systems, the ECM precisely controls injection timing by energizing individual injector solenoids or piezo actuators at the calculated crank angle.

Question 3

During a hydraulic pump performance test, measured flow is 15% below the manufacturer's specification at rated pressure and speed. This result MOST likely indicates:

Accepted Answer

Excessive internal pump leakage (volumetric inefficiency)

Answer

A 15% flow deficit at rated conditions is the classic signature of worn pump internals causing volumetric inefficiency through internal slippage.

Question 4

When inspecting a boom cylinder on an excavator for structural integrity, a CEM notices a hairline crack at the base of a trunnion mount weld. The CORRECT action is:

Accepted Answer

Immediately remove the machine from service for weld repair evaluation

Answer

Cracks at structural weld locations are a critical safety defect requiring immediate removal from service and professional structural assessment.

Question 5

A technician measures 0.5 volts on the signal wire of a 0–5V pressure sensor while the system is at high pressure. This reading MOST likely indicates:

Accepted Answer

An open circuit or failed sensor producing a low-clamp signal

Answer

A 0–5V pressure sensor should produce 4–4.5V at high pressure; 0.5V is near the zero-pressure value and suggests an open-circuit or failed sensor.

(CEM) Certified Equipment Manager Practice Test

(CEM) Certified Equipment Manager Practice Test

CEM Technical Skills & Application 3