Professional Diesel Mechanic Interview Preparation Guide

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A valve assisted by a spring,'which is opened by a difference of pressure acting in one direction and closed by a difference in pressure acting in the opposite direction.

To harden the outer surface of metal to a given case or shell depth, while leaving the inner portion soft to absorb shocks and allow bending.

A sensor which sends a range of voltages in DC to the ECM to describe, for example, coolant temperature, engine oil pressure, or atmospheric pressure.

A device that reduces both exhaust smoke and noise by slowing engine acceleration slightly until adequate turbocharger boost pressure is present.

Speeds at which the frequency of the power strokes synchronize with the crankshaft's natural frequency. If the engine is operated at one of its critical speeds for any length of time, a broken crankshaft may result.

Ratio of power output in the form of brake horsepower to equivalent power input in the form of heat from fuel. Typical brake thermal effidency ranges from thirty to forty-two percent.

Automobiles, trucks, buses, marines, and construction areas are popular types that are based on diesel engines.

A rotating component of irregular shape. It is used to change the direction of the motion of another part moving against it, e.g., rotary into reciprocating or variable motion.

Either of the two positions when the crank and connecting rod are in a straight line at the end of the stroke. The total piston travel is the distance between the two dead center positions.

Normally used in control circuits, relay is a switch driven by electricity and rules over contactor by virtue of low amperage contacts.

A device which holds open the intake or exhaust valve, thereby permitting the engine to be turned over without compression. This is one method of engine braking where by the power stroke is cancelled.

The taper at the thread end of a tap or the throat of a die, made by cutting away the crests of the first few threads. This distributes the work of cutting over several threads and acts as a guide in starting the tap or die. The chamfer is relieved to facilitate cutting.

Combustion which occurs without change in pressure. In an engine, this is obtained by a slower rate of burning than with constant volume combustion.

A thin sandwich strip of two metals with very dif- ferent heat expansion rates that bends to the left or the right due to heat caused by resistance to voltage.

Diesel mechanic is typically responsible to operate, handle, maintain and repair diesel engines that are used to run any machinery including vehicles, generators and other machinery.

This graphite or copper made conducting element maintains sliding electrical contact between static and moving element.

Also called a capaciator, this electronic component CI stores up electric charge until a set svoltage is reached; then a high but rapidly decaying current flows through the circuit until finally the voltage difference between the two leads reaches zero.

The pressure exerted by the atmosphere, averaging 14.7 psi at sea level with a decrease of approximately 1/4 lb per
1,000 ft of altitude gained.

Diesel mechanics are basically responsible for the troubleshooting, upkeep, maintenance, and repair of diesel engines. This may include vehicle engines, generators and plant machinery that requires diesel to make it run.

A utility device that converts mechanical energy into electrical energy, available either in the form of direct or alternating current.

In a single acting engine, the volume swept by all pistons in making one stroke each. The displacement on one cylinder in cubic inches is the circular area (in square inches) times the stroke (in inches).

Lowest compression ratio at which any particular fuel will ignite by compression. The lower the critical compression ratio the better ignition qualities the fuel has. (Gasoline engine, 4:1; oil engine, 7:1; diesel engine, 12.5:1.)

The surface hardness of a metal, alloy, or similar material according to l.A. Brinell's method of measurement. A metal's surface is struck at a given force by a rigid steel ball of a given diameter, and the indentation is measured.

A diesel mechanic must employ two important skills. First is analytical mind to be able to evaluate any issue occurred in the engine. Second is ability to read and perceive instructions manuals and blueprints of the engines since each engine has different design and small engine routes can end up in complex issues.

A mechanical device that converts mechanical energy into electrical energy through electromagnetic induction process.