Valve System Components

TM 9-2320-312-24-2

Systems Operation Section

Air Inlet Heater

Valve System Components

The engines are equipped with an electric heater

that is located behind the air inlet elbow. The

electric heater has two functions:

Aid in starting

Aid in white smoke cleanup during start-up

Under the proper conditions, the ECM turns on

the electric heater. The following conditions are

evaluated prior to activating the electric heater:

Jacket water coolant temperature

Inlet manifold air temperature

Ignition switch position

Duration of time

The system is capable of delivering heat for 30

seconds prior to start-up and during cranking of the

engine. After the engine has started, the system is

capable of delivering heat constantly for 7 minutes,

or the system can cycle the heat for 13 minutes.

During the heating cycle, the heat is on for ten

seconds and the heat is off for ten seconds.

g00294195

Illustration 27

If the air inlet heater malfunctions, the engine will

Valve System Components

still start and the engine will still run. There may be

(1) Rocker arms. (2) Bridge. (3) Spring. (4) Pushrods. (5) Exhaust

a concern regarding the amount of white smoke that

valve. (6) Inlet valves. (7) Lifter. (8) Camshaft lobe.

is present. Also, there may be a concern regarding

the need for an alternative starting aid.

The valve system components control the flow of

inlet air into the cylinders during engine operation.

System Components

The valve system components also control the flow

of exhaust gases out of the cylinders during engine

The system of the air inlet heater consists of the

operation.

following basic components:

The crankshaft gear drives the camshaft gear

Relay of the air inlet heater

through an idler gear. The camshaft must be

timed to the crankshaft in order to get the correct

Heater element

relation between the piston movement and the valve

movement.

Coolant temperature sensor

The camshaft has two camshaft lobes for each

Inlet air temperature sensor

cylinder. The lobes operate the inlet and exhaust

valves. As the camshaft turns, lobes on the camshaft

ECM

cause lifters (7) to move pushrods (4) up and down.

Upward movement of the pushrods against rocker

Indicator lamp

arms (1) results in downward movement (opening)

of valves (5) and (6).

Each cylinder has two inlet valves and one exhaust

valve. Valve springs (3) close the valves when the

lifters move down.