Installation Of Fuel-Air Bleed Nozzle; Ignition System Maintenance; Description And Principle Of Operation; Inspection Of Magneto - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERV CE MANUAL
a. Clean the nozzle with acetone or equivalent and blow out all foreign particles. Do not use wire or
other hard objects to clean orifices. (Refer to the latest revision of Lycoming Service Instruction No. 1275.)
b.
Inspect and replace nozzle O-rings if found to be cracked, brittle or distorted.
c. A test procedure for air bleed nozzles is described on latest revision of Lycoming Service
Instruction No. 1275.
8-69. INSTALLATION OF FUEL-AIR BLEED NOZZLE.
a. It is important for the nozzles to be correctly positioned with the bleed hole upward.
b.
Install the nozzles and torque to 60 inch-pounds.
c. Ascertain that the O-rings are properly installed on the nozzle stem and install the nozzle shroud.
(Refer to Figure 8-11.)
d. Connect the vent to the nozzle shroud.
e. Install the spring and spring retainer on the nozzle stem.
f. Connect the fuel line to the nozzle and clamp the fuel lines as described in latest revision of Lycom-
ing Service Bulletin No. 335.
g. Install the engine cowl. (Refer to paragraph 8-6.)
8-70. IGNITION SYSTEM MAINTENANCE.
8-71. MAGNETO.
8-72. DESCRIPTION AND PRINCIPLE OF OPERATION.
The D-2230 series magnetos feature two electrically independent ignition circuits in one housing. A single
four pole rotor provides the magnetic energy for both circuits. This magneto is designed to be used with a
starting vibrator unit. The magneto has two separate breaker cams. The lower cam operates the main breakers
for both magneto circuits. The upper cam operates the left magneto retard breaker. Suppression of radio
interference is accomplished by feed-thru capacitors, which are mounted in the magneto cover and forms a
part of the magneto harness assembly.
With the magneto switches ON and the starter switch depressed the right side of the magneto is
grounded and rendered inoperative while left side of the magneto (with retard breaker) continues to
function. At the slow cranking speed of the engine the vibrator provides the high energy spark necessary to
fire the spark plugs. The vibrator provides interrupted battery current to the primary coil of the magneto.
The pulsating DC current is then stepped up by transformer action, producing a shower of sparks at the
plugs for improved starting. When the engine fires and begins to increase speed, the starter switch is
released, which in turn de-energizes the starter, opens the vibrator circuit and retard breaker circuit, thus
rendering them inoperative. The right side of the magneto is no longer grounded and thus both magneto
sides are simultaneously firing in full advance.
8-73. INSPECTION OF MAGNETO.
After the first 50 hour period and every 100 hours thereafter, the magneto ignition system should be
checked. If engine operating troubles develop which appear to be caused by the ignition system, it is
advisable to check the spark plugs and wiring first before working on the magneto. Should trouble appear
definitely associated with the magneto, the most effective measure is to install a replacement magneto
which is known to be in satisfactory condition and send the suspected unit to the overhaul shop for test
and repair. Should this not be possible, a visual inspection of the following items may disclose the source of
trouble.
a. Check the lead terminals for definite contact with spring contacts in outlets.
b. Remove the harness outlet cover from the magneto and inspect for the presence of moisture and
carbon tracking due to moisture.
c. Check contact springs in distributor block for evidence of spark erosion.
d. Check height of contact springs (0.422 maximum from top of block tower to spring.) (Refer to Figure
8-12.)
Revised: 3/11/81
2112
POWER PLANT