Piper Arrow IV, Maintenance Manual

Page: 632 / 752

INSTALLATION OF HARNESS.
Before installing the harness plate on the magneto, check the mating surfaces for cleanliness. Spray the
entire face of the grommet with a light coat of Plastic Mold Spray, SM-O-O-TH Silicone Spray or equivalent.
This will prevent the harness grommet from sticking to the magneto distributor block.
1. Place the harness terminal plate on the magneto and tighten the nuts around the plate alternately to seat
the cover squarely on the magneto. Torque the nuts to 18 to 22 inch-pounds.
2. Route the ignition wires to their respective cylinders as shown in Figure 74-21.
3. Clamp the harness assembly in position.
4. Connect the leads to the spark plugs.
SPARK PLUGS.
REMOVAL OF SPARK PLUGS.
1. Loosen the coupling nut on the harness lead and remove the terminal insulator from the spark plug
barrel well. (A crows foot adapter is needed to remove the lower spark plugs.)
—NOTE—
When withdrawing the ignition cable lead connection from the
plug, care must be taken to pull the lead straight out and in line
with the center line of the plug barrel; otherwise, a side load will
be applied which frequently results in damage to the barrel
insulator and connector. If the lead cannot be removed easily in
this manner, the resisting contact between the neoprene collar
and the barrel insulator will be broken by a rotary twisting of the
c o l l a r. Avoid undue distortion of the collar and possible side
loading of the barrel insulator.
2. Remove the spark plug from the engine. In the course of engine operation, carbon and other
combustion products will be deposited on the end of the spark plug and will penetrate the lower threads to
some degree. As a result, greater torque is frequently required for removing a plug than for its installation.
Accordingly, the torque limitations given do not apply to plug removal, and sufficient torque must be used to
unscrew the plug. The higher torque in removal is not as detrimental as in installation, since it cannot stretch
the threaded section. lt does, however, impose a shearing load on this section and may, if sufficiently severe,
produce a failure in this location.
—NOTE—
Torque indicating handle should not be used for spark plug
removal because of the greater torque requirement.
3. Place spark plugs in a tray that will identify their position in the engine as soon as they are removed .
—NOTE—
Spark plugs should not be used if they have been dropped.
Effectivity 74-22-01
PA-28RT-201T Page 74-19
December 1, 1978
3E4
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL