INSTALLATION - TM-10-3930-607-150123

ELECTRICAL

the gasket, then using a proper fitting socket wrench,

CAUTION: Before adjusting gap, file

tighten 2/3 additional turn. Care must be exercised

center electrode flat. In adjusting the

when tightening.

spark plug gap, never bend the

center electrode which extends

Spark plugs which are not tightened

through the porcelain center as this

correctly will result in too high an operating temperature

may break the lower insulator.

if too loose, or distortion of the spark plug body and

Always

make

adjustments

change in gap setting or damage to the gasket if too

bending the ground or side

tight.

electrode. (Fig. 43)

CHECKING GAUGES AND INDICATOR LIGHTS

A. GENERAL

Do not remove any unit from the truck unless it is known

to be defective.

Check wiring, connections and indicator lights before

condemning any unit.

B. ENGINE OIL PRESSURE AND HYDRAULIC OIL

The transmission temperature warning light should be

checked periodically for good connections and lighting

ability.

Although the oil pressure gauge functions normally, the

oil pressure should be checked to help determine engine

condition.

Substitute an oil pressure gauge for the oil pressure

sending unit, to determine the oil pressure.

C. CHECKING GAUGES

Figure 43.

Before checking a gauge or sending unit, make sure all

D. INSTALLATION

electrical connections are tight and free of dirt or

moisture.

Be certain that the old gasket is removed

before installation of plug, and that the gasket seat is

Wiring should be checked for broken or frayed insulation

clean and smooth. Check also that the spark plug

which may cause a short or ground in the circuit.

threads and the cylinder head threads are not dirty or

damaged. Dirty or damaged threads cause a faulty

Any of these causes may have been the reason for

torque reading, resulting in incorrect installation and

failure.

consequent poor spark plug life and faulty operation.

The following equipment is necessary to make a

Install the spark plugs in the engine with

complete check of these gauges:

new gaskets and tighten. If torque wrench is not

available, turn plugs in until they are finger-tight against

B-86