Ignition And Electrical System - Lycoming O-290 Operator's Manual

LYCOMING OPERATOR'S MANUAL
O-235 AND O-290 SERIES
The procedures described in this section are provided to guide and instruct personnel in performing such
maintenance operations that may be required in conjunction with the periodic inspections listed in the
preceding section. No attempt is made to include repair and replacement operations that will be found in the
applicable Lycoming Overhaul Manual.

1. IGNITION AND ELECTRICAL SYSTEM.

a. Ignition Harness and Wire Replacement – In the event that an ignition harness or an individual lead is
to be replaced, consult the wiring diagram to be sure harness is correctly installed. Mark location of
clamps and clips to be certain the replacement is clamped at correct locations.
b. Timing Magnetos to Engine – Although several combinations of magnetos are used on this series
engines, (see Table of Models for model application) the timing procedures, in the following
paragraphs, are the same for all magnetos.
Either the impulse coupling or retard breaker magneto (whichever is applicable) is installed
on the left side of the engine.
(1) Remove the spark plug from No. 1 cylinder and place a thumb over the spark plug hole. Rotate the
crankshaft in direction of normal rotation until the compression stroke is reached, this is indicated
by a positive pressure inside the cylinder tending to push the thumb off the spark plug hole.
Continue rotating the crankshaft in direction of normal rotation until the advance timing mark on
the front face of the starter ring gear is in exact alignment with the small hole located at the two
o'clock position on the front face of the starter housing. Consult specification for correct timing
mark for you installation. At this point, the engine is ready for assembly of the magnetos.
All timing procedures, except positioning the magneto in the number one cylinder advance
engine firing position, are the same for all magnetos.
The method of positioning the Slick magnetos in the number one cylinder advance engine firing
position is contained in the following paragraphs. The method for Bendix magnetos may be found
on page 5-3.
Impulse Coupling Magneto – Hold the No. 1 lead wire spring 1/16 in. to 1/8 in. away from the
magneto frame and turn the impulse coupling one click at a time until a strong spark jumps
between the spring and the frame. Hold the magneto firmly so the coupling will not move beyond
the point where it trips and the spark occurs. Reverse the rotation approximately 25° until the
timing pin hole appears in the center of the vent plug hole. Hold the rotor by inserting the timing
pin, and line the timing pin with the center of the vent plug hole.
SECTION 5
MAINTENANCE PROCEDURES
NOTE
MAINTENANCE PROCEDURES
SECTION 5
5-1