Piper Navajo PA-31 Service Manual page 624

PIPER NAVAJO SERVICE MANUAL
9-53. 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.
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
bypass valve and back to the container.
NOTE
It is advisable to have full 28-volt DC current when running
the pump in order to obtain the correct pressure of 30 ± 2 psi
for 43382-02 pump (used on PA-31-300 and shown in Figure
9-12a); 44 + 1 psi for pumps 42113-02 or -06 (used on
PA-31-310 or as a replacement on PA-31-300, shown in
Figure 9-12), or 40
2 psi for 42113-05 pump (used on
PA-31-325, shown in Figure 9-12) maximum no flow.
e. Run the pump with the bypass valve open until a steady flow of fuel is obtained.
Then close the bypass valve and check the pressure gauge for the proper maximum no flow,
reading Note above. On PA-31-325 if the boost pump is operated in conjunction with
electric fuel pump, the pressure reading should be 47 to 54 psi, maximum no flow. Do not
keep the bypass valve closed for more than one minute during pump operation and
adjustment.
f.
Loosen the locknut and turn the adjustment screw until the gauge reading agrees
with the above noted pressure. Repeat steps e and f until the proper pressure is obtained.
Lock the adjustment screw with the locknut.
g. Disconnect the power source from the pump and remove the fuel lines from the
pump.
9-54. 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 bypass 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 bypass valve on the test line and start the pump.
NOTE
It is advisable to operate the opposite engine in order to
supply the full 28-volt DC current to the pump. Observe all
safety precautions when engine is running.
Revised: 9/23/80
FUEL SYSTEM
3C8