Spark Plugs - TM-10-3930-630-120080

TM 10-3930-630-12

(3) Use a fine mill file and file electrodes

(8) Install No. 1 spark plug and connect

to provide a square or flat surface at gap area

wire (para 4-54).

e. Adjustment.

(9) If removed, install timing cover on the

top of flywheel housing. Install battery box and battery

(1) Adjust spark plug gap by bending

(para 446).

outside electrode. Do not bend center electrode.

(2) Use a round feeler gage to measure

4-54.

Spark Plugs

gap between electrodes. Adjust gap to 0.025 inch

(0.634 mm).

Testing.

a. General.

The four spark plugs are

(1) Test all spark plugs after cleaning and

mounted along the left side of the cylinder head.

b. Inspection.

adjusting. Test plugs in a standard plug machine.

Discard all plugs showing an unsatisfactory test.

(1) Lift seat up and tilt forward and prop in

g. Installation.

open position.

(1) Use new copper gaskets and install

(2) Inspect spark plugs and wires for

plugs in cylinder head.

cracks and breaks in insulation and porcelain.

(2) Tighten plugs by hand and then

(3) Inspect contact at top of plug and in

tighten plugs to 30 to 40 pound-feet (40.6 to 54.2 N⋅m).

wires for good condition and clean contact surfaces.

(4) Clean dirt and grease from plugs and

(3) Connect spark plug wires (2, fig. 4-41)

wires.

to plugs.

c. Removal

4-55.

Ignition Coil

(1) Disconnect spark plug wires (2, fig. 4-

41) from spark plugs. Blow dirt from spark plug wells

a. General. High voltage required to provide

with compressed air.

(2) Remove spark plugs (3) from cylinder

a spark for engine operation is provided by the ignition

head using a suitable spark plug wrench.

coil The coil (10, fig. 441) is mounted on a bracket on

(3) Remove copper gaskets from spark

the right side of the engine block. A 50-ohm resistor is

plug wells.

connected in series with the coil A limit of 12 volts is

d. Cleaning.

provided to the primary side of the coil from the

(1) Scrape carbon and lead deposits from

alternator.

b. Amperage Draw Test. Open right side

electrodes and insulator body of plugs.

(2) Sand blast spark plug electrodes with

panel and lift seat into open position.

care. Do not leave plug in sand blast machine too long.

(1) Connect the ignition coil in a circuit as

Damage to glaze could result.

shown in figure 4-44.

Figure 4-44. Ignition coil test wiring..

4-52