Piper Navajo PA-31 Service Manual page 44

PIPER NAVAJO SERVICE MANUAL
2-21. FUEL SYSTEM.
2-22. SERVICING FUEL SYSTEM. Al intervals of 50 hours or 90 days, whichever comes first, clean the
screens and bowl in each fuel filter unit located between each wing and the fuselage. Remove and clean the
filters in accordance with the instructions outlined in Section IX. Additional service information may also
be found in Section IX. Inspection intervals of the various fuel system components may be found in
Section III.
2-23. FILLING FUEL CELLS. The fuel cells of each wing are filled through filler necks located on the
forward slope of the wings, outboard of the engine nacelles.
a. Observe all required safety precautions for handling gasoline.
b. Fill the cells with fuel as specified on the placard adjacent to the filler neck or as indicated in
Table II-I.
2-24. DRAINING MOISTURE FROM FUEL SYSTEM. To facilitate draining the fuel system filter bowls.
lines and fuel cell of moisture and foreign matter, drains are incorporated in the bottom of each filter bowl.
in the system cross-feed line and the inboard end of each fuel cell.
a. To flush either filter bowl, open the access door located on the panel between the underside of
the wing and fuselage. Push up on the arms of the drain valve for a few seconds with the fuel selector valve
on one cell, then change the selector valve to the other cell and repeat the process. Allow enough fuel to
flow each time to clear the fuel line as well as the fuel filter bowl. The same procedure will apply to the
cells of the opposite side.
b. To flush the cross-feed line, open the cross-feed valve and push up on the arms of the drain valve
for a few seconds. The drain valve is located on the left panel aft of the filter bowl access door.
c. To flush the fuel cells, push up on the arms of each cell drain and allow to flow for a few
seconds.
2-25. DRAINING FUEL SYSTEM. The bulk of the fuel may be drained from the system by opening the
valve at the inboard end of each fuel cell. Push up on the arms of the drain valve and turn counter-clockwise
to hold the drain in the open position. The remaining fuel in the system may be drained through each filter
bowl. Any individual cell or compartment may be drained by closing the selector and cross-feed valves and
then draining the desired component.
2-26. BRAKE SYSTEM.
2-27. SERVICING BRAKE SYSTEM. The brake system incorporates a hydraulic fluid reservoir through
which the brake system is periodically serviced. Fluid is drawn from the reservoir by the brake master
cylinders to maintain the volume of fluid required for maximum braking efficiency. Spongy brake pedal
action is often an indication that the brake fluid reservoir is running low on fluid or air is in the system.
Instructions for filling the reservoir are given in Paragraph 2-28. When found necessary to accomplish
repairs to any of the brake system components or bleed the system, these instructions may be found in
Section VII.
2-28. FILLING BRAKE CYLINDER RESERVOIR. Use the MIL-H-5606 only. Check fluid level every 50
hours and replenish as necessary. No adjustment of the brakes is necessary, though they should be checked
periodically per instructions given in Section VII.
Reissued: 10/12/79
HANDLING AND SERVICING
1B20