10.
For spark plug end, mount M-1747 drive plate in a bench vise. Set hex ferrule in drive plate slot. Drive M-1458 drive ferrule flush against the hex ferrule using the M-1744 drive tool. (Refer to Figure 74-17.) Or, press into place using T-109 pressing tool.
11.
For magneto end of wire, insert wire through hole in M-1569 harness cap so shielding is through hole as shown in Figure 74-18.
12.
Install an M- 1458 male tapered drive ferrule over insulation and under shielding as in step 9, then drive ferrule into M-1569 housing using M-1744 drive tool, similar to step 10. (Refer to Figure 74-19.) Or, press into place using T-109 pressing tool.
13.
Clamp threaded end of M-1498 electrode screw in T-111 or M-1742 pin vise. Insert tapered pin of electrode screw into center of coiled conductor by turning pin vise counterclockwise and pushing at same time until screw is flush with insulation. This is done at both ends of the wire assembly. (Refer to Figure 74-20.)
14.
On magneto end of wire, place M-1738 insulator sleeve (brown, 0.75 inch long) over silicone insulation. On spark plug end of wire, use green M-1677 insulator sleeve. (Refer to Figure 74-21.)
15.
Turn M-2929 spring clockwise on electrode screw three full turns until end is flush with first large coil of spring. This applies to both ends of wire. (Refer to Figure 74-22.)
74-20-00 Page 74-22 Issued: April 1, 1997
3I4
74-20-00 Page 74-23 Revised: February 28, 2002
INSTALLATION OF HARNESS
1.
Before installing harness on magneto, check mating surfaces for cleanliness.
2.
Place harness terminal plate on magneto and tighten nuts around plate alternately to seat cover squarely on magneto.
—Note—
The left magneto is wired to fire all top spark plugs in this engine. The right magneto fires all bottom plugs.
3.
Route ignition wires to their respective cylinders.
4.
Clamp harness assembly in position and replace engine baffle plate.
5.
Connect leads to spark plugs.
THIS SPACE INTENTIONALLY BLANK
74-20-00 Page 74-Issued: April 1, 1997
3I6
SPARK PLUGS
REMOVAL OF SPARK PLUGS (REFER TO FIGURE 71-23.) — CAUTION —
WHEN WITHDRAWING IGNITION CABLES LEAD CONNECTION FROM PLUG, CAREFULLY PULL LEAD STRAIGHT OUT AND IN LINE WITH CENTER LINE OF PLUG BARREL; OTHERWISE, A SIDE LOAD WILL BE APPLIED WHICH FREQUENTLY RESULTS IN DAMAGE TO BARREL INSULATOR AND CONNECTOR. A LEAD CANNOT BE REMOVED EASILY IN THIS MANNER, RESISTING CONTACT BETWEEN NEOPRENE COLLAR AND BARREL INSULATOR WILL BE BROKEN BY A ROTARY TWISTING OF COLLAR. AVOID UNDUE DISTORTION OF COLLAR AND POSSIBLE SIDE LOADING OF BARREL INSULATOR.
1. Loosen coupling nut on harness lead and remove terminal insulator from spark plug barrel well.
—CAUTION— DUE TO GREATER TORQUE VALUE REQUIREMENTS, TORQUE WRENCHES SHOULD NOT BE USED TO REMOVE SPARK PLUG. — CAUTION — DO NOT ALLOW FOREIGN OBJECTS TO ENTER SPARK PLUG HOLE.
2. Remove spark plug from engine.
a.
In the course of engine operation, carbon and other combustion products are deposited on the end of spark plugs and will penetrate lower threads to some degree. As a result, a greater torque is required for removing a plug than for installation. Torque limitations given do not apply to plug removal, as sufficient torque must be used to unscrew plug.
b.
The higher torque required to remove plugs is not as detrimental as in installation, since it cannot stretch the threaded section. It does, however, impose a shearing load on this section and may, if sufficiently severe, produce a failure in this location.
3.
Immediately upon removal, place spark plugs in a tray in a manner that will identify their position in the engine.
4.
Removal of seized spark plugs in cylinder is done by application of liquid carbon dioxide (CO2) by a conical metal funnel adapter with a hole at the apex just large enough to accommodate the funnel of a 20 lb bottle. (Refer to Figure 74-23.) When a seized spark plug cannot be removed by normal means, funnel adapter is placed over and around spark plug. Place funnel of CO2 bottle inside funnel adapter and release carbon dioxide to chill and contract spark plug. Break spark plug loose with a wrench. A warm cylinder head at the time carbon dioxide is applied will aid in removal of excessively seized plug.
74-20-00 Page 74-25 Issued: April 1, 1997
CHART 7402. COUPLING TORQUE
Spark Plug Torque
Coupling Threads (Ib.-in.)
5/8-24 90 - 95
INSPECTION AND CLEANING OF SPARK PLUGS
1. Visually inspect each spark plug for the following non-repairable defects.
a.
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