Engine Performance & Diagnostics Flashcards
7 cards from real LEC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Engine Performance & Diagnostics flashcards as text
When conducting a pre-departure engine inspection, which reading on a diesel locomotive indicates the engine is ready for service?
Answer: Oil pressure within normal operating range and coolant temperature above minimum warm-up threshold
Engine readiness requires oil pressure within the normal operating band and coolant temperature warmed to the minimum operational threshold specified by the manufacturer.
A locomotive engineer notices that exhaust pyrometer readings are uneven across cylinders during a road test. Cylinders 3 and 7 read significantly lower than the others. This indicates:
Answer: Those cylinders are likely misfiring or have reduced fuel delivery
Low exhaust temperature on specific cylinders indicates reduced combustion in those cylinders, typically from faulty injectors, low compression, or valve issues.
What is the function of the engine protection system's 'hot engine' shutdown feature?
Answer: To automatically shut down the engine when coolant temperature exceeds a safe limit to prevent damage
The hot engine shutdown automatically cuts fuel and stops the engine when coolant temperature exceeds the maximum safe limit, preventing thermal damage to engine components.
A locomotive is experiencing frequent low-oil-pressure alarms only at higher throttle notches. The MOST likely cause is:
Answer: Worn main bearings creating excessive clearance that bleeds off pressure under high load
Pressure loss only at high load suggests excessive bearing clearance that allows oil to flow through the clearances faster than the pump can maintain pressure.
What does a 'motoring' condition mean in the context of a diesel-electric locomotive?
Answer: The traction motors are driving the wheels in reverse of the direction of travel, consuming rather than generating power
Motoring occurs when traction motors draw power from an outside source (such as a lead unit) and drive the axles, rather than being driven by the axles as in dynamic braking.
During engine diagnostics, a locomotive technician finds the fuel rack is at maximum travel but horsepower output is below specification. Which component failure could cause this?
Answer: Failed fuel transfer pump reducing supply pressure to injectors
A failed fuel transfer pump causes low fuel supply pressure, so even with the rack fully open the injectors cannot deliver adequate fuel volume for rated horsepower.
Which condition would cause a locomotive diesel engine to 'hunt' or surge at a steady throttle notch?
Answer: Faulty or unstable governor unable to maintain constant engine speed
Engine hunting or surging at a fixed throttle position is a classic symptom of a faulty governor that cannot maintain stable speed control.