Piper Navajo PA-31 Service Manual page 620

PIPER NAVAJO SERVICE MANUAL
9-45. ADJUSTMENT OF ELECTRIC FUEL PUMP (BENCH TEST).
a. Ascertain that the pump is sufficiently lubricated to prevent damage if run dry for a
period greater than five minutes.
b. Connect the electric leads to a 28-volt DC power source. (The black lead is the
negative lead.)
c. Using a suitable container with the proper octane fuel, connect a fuel line from the
container to the inlet side of the pump.
d. Connect another line from the outlet side of the pump to a pressure gauge and
by-pass valve and back to the container.
e. Run the pump with the by-pass valve open until a steady flow of fuel is obtained.
Then close the by-pass valve and check the pressure gauge for the proper reading of 42 psi
maximum, no flow. Do not keep the by-pass valve closed for more than one minute during
pump operation and adjustment.
f.
Loosen the locknut and turn the adjusting screw until there is a reading of 42 psi
maximum, no flow, on the gauge. Repeat steps e and f until the proper pressure is obtained.
g. Disconnect the power source from the pump and lock the adjustment screw with the
locknut. Remove the fuel lines from the pump.
9-46. ADJUSTMENT OF ELECTRIC FUEL PUMP (IN THE AIRPLANE).
a. With the access panels removed and the fuel selector in the OFF position, remove
the fuel line from the outlet end of the pump.
b. Connect a test line with a by-pass valve and pressure gauge to the outlet end of the
pump.
c. Place a container below the pump to catch any fuel from the test line during the
adjustment of the pump.
d. Turn the fuel selector on; open the by-pass valve on the test line and start the pump.
e. When a steady flow of fuel is obtained, close the by-pass valve and check the reading
on the pressure gauge. It should read 42 psi, maximum no flow. Do not keep the by-pass
valve closed for more than one minute during pump operation and adjustment.
f. Loosen locknut on adjusting screw and turn screw to obtain the proper pressure of
45 psi maximum, no flow. Repeat steps d and e until adjustment is complete. Lock
adjusting screw with locknut.
g. Turn off fuel pump and close fuel selector. Remove the test line from the pump.
h. Reconnect the original fuel line to the pump. Open fuel selector and run the pump
to check for any fuel leaks.
i.
Shut off the pump; close the fuel selector and replace and secure the access panels.
Revised: 9/23/80 FUEL SYSTEM
3C4