Page 79 - Apprentice Manual_Neat

S2-Q52.) Which tool is used to check ignition timing?

a.) Feeler gauge
Used to tolerances such as points gap or spark plug gap.
b.) Voltmeter
Used to measure voltage and would not be useful in determining when a spark occurred.
c.) Timing meter
Not an appropriate response for engine timing.
d.) *Timing light
Correct. A timing light fires a strobe light when it detects energy in the sparkplug wire. This
strobe will illuminate the timing mark on the flywheel or other device directly connected to the
crank. When it is illuminated, one can compare its position to a reference mark on the block.

S2-Q53.) The purpose of an aftercooler or intercooler in a diesel engine is to?

a.) *Reduce inlet air temperature
Is correct because the idea is to pass inlet air past a radiator in the intake manifold to reduce
turbocharged hot air temperature down to engine operating temperature.
b.) Reduce exhaust temperature
Is wrong because while exhaust air temperature does somewhat relate to inlet air temperature, there
are many other variables that directly relate to exhaust air temperature such as load, speed, fuel
quality, compression temperature.
c.) Heat cooling system up faster
Is wrong because while heat is exchanged in the aftercooler to the coolant during warm-up and at all
other times, this is a bi-product and not a purpose of an aftercooler.
d.) Cool the fuel
Is wrong because aftercoolers have nothing to do with the fuel system.

S2-Q54.) The temperature of lube oil in a diesel engine must be controlled because?

a.) Temperature is not important, only pressure is!
Is wrong because there is a relationship of high oil temperature to low oil viscosity and vice versa
affecting engine performance.
b.) The higher the temperature of oil, the lower the viscosity in high temps.
Is correct because the oil thins as it gets hotter and too thin of oil can lead to increased engine wear.
c.) Oil oxidizes and becomes carbonaceous at a temperature over 250 degrees F.
Is correct because as oil rises above 250 degrees F, it actually will thicken then from oxidation where
carbon forms in the oil as a solid.
d.) * B and C of the above
Is the most correct because b and c are correct.

Page 71 - EGSA Apprentice Certification Program Study Guide