Piper Navajo PA-31 Service Manual page 532

PIPER NAVAJO SERVICE MANUAL
an alternator, geared starter, hydraulic pump and pressure pump. Engine mounts are steel
tubing construction attached at the fire wall and incorporate vibration absorbing mounts.
The exhaust stacks and extensions are positioned one for each bank of cylinders. The stack
on the right side has a heat muff on it to heat the alternate air plenum. Both stacks merge
into one at the lower aft end of the engine nacelle.
The lubrication system is of the pressure wet sump type. The oil pump, which is located
in the accessory housing, draws oil through a drilled passage leading from the oil suction
screen located in the sump. The oil from the pump then enters a drilled passage in the
accessory housing, which feeds the oil to a threaded connection on the rear face of the
accessory housing, where a flexible line leads the oil to the external oil cooler. Pressure oil
from the cooler returns to a second threaded connection on the accessory housing from
which point a drilled passage conducts oil to the oil pressure filter. In the event that cold oil
or an obstruction should restrict the oil flow to the cooler, an oil cooler bypass valve is
provided to pass the oil directly from the oil pump to the oil pressure filter.
The oil pressure filter element, located on the accessory housing, is provided as a means
to filter from the oil any solid particles that may have passed through the suction screen in
the sump. After being filtered in the pressure filter, the oil is fed through a drilled passage to
the oil pressure relief valve, located in the upper right side of the crankcase in front of the
accessory housing.
This relief valve regulates the engine oil pressure by allowing excessive oil to return to
the sump, while the balance of the pressure oil is fed to the main oil gallery in the right half
of the crankcase. Residual oil is returned by gravity to the sump, where after passing
through a screen it is again circulated through the engine.
8A-3. TROUBLESHOOTING. Troubles peculiar to the powerplant are listed in Table
VIII-II in Section VIII, along with their probable causes and suggested remedies. When
troubleshooting engines, ground the magneto primary circuit before performing any checks
on the ignition system.
NOTE
This engine is not turbocharged. When using Table VIII-II in
accordance with this engine, disregard the troubleshooting
portion of the Table labeled Turbocharger.
8A-4. ENGINE COWLING. (Refer to Engine Cowling, Section VIII.)
8A-5. ENGINE COWL FLAP. (Refer to Engine Cowl Flap, Section VIII.)
8A-6. PROPELLER. Use Table VIIIA-I in conjunction with Table VIII-I and Propeller,
Section VIII.
Reissued: 10/12/79
POWERPLANT
2K10