Piper Navajo PA-31 Service Manual page 625

e. When a steady flow of fuel is obtained, close the bypass valve and check the reading
on the pressure gauge. It should read 30 ± 2 psi for pump 43382-02 (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. On PA-31-325 if the boost pump
is operated in conjunction with electric fuel pump, the pressure 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 locknut on adjustment screw and turn the screw to obtain the proper
pressure noted above. Repeat steps d and e until adjustment is complete. Lock the
adjustment screw with the locknut.
g. Turn off fuel pump and close fuel selector. Shutdown opposite engine if it was used
to supply full 28-volts DC current. Remove the test line from the pump.
h. Reconnect the original fuel line to the pump. Open the fuel selector and run the
pump to check for any fuel leaks.
i. Shut off the pump; close the selector and replace and secure the access panels.
9-55. INSTALLATION OF ELECTRIC FUEL PUMP.
a. Connect the fuel pump and fuel filter. Tighten the jam nut on the fitting between
the pump and filter to allow the "O" ring to seat on the non-threaded portion of the fitting.
b. Position the fuel pump and filter on the mounting brackets and secure with bolts.
c. Connect the fuel lines to the pump and filter.
d. Connect the electrical wires to the pump motor.
e. Turn the fuel selector valve on and check for leaks.
f. Install the access panels and secure them.
9-56. ELECTRIC FUEL BOOST PUMP. (PA-31-325)
9-57. ADJUSTMENT OF FUEL BOOST PUMP. The fuel boost pump has been adjusted by
the manufacturer at 9-12 PSIG, no flow. Should a pressure test indicate a value substantially
lower, contact the manufacturer for adjustment information.
9-57a. FUEL BOOST PUMP WARNING SENSOR OPERATIONAL TEST. Use the
press-to-test button to check the bulb. Ascertain that the system is fueled. Place mixture
control in idle cut off, selector and firewall shutoff valves on and crossfeed off, boost pumps
circuit breakers off, lights should come on. Push breakers on, one at a time, and observe that
the proper light goes out. Turn boost pumps off, lights should come on. If lights do not
come on, open throttle and mixture control to relieve pressure and then close; the lights
should come on and stay on.
NOTE
Do not run pumps at no flow for more than one minute.
Troubleshoot the electrical wiring and refer to the paragraphs on adjustment of fuel boost
pumps and warning sensors, if the operational test does not check out.
PIPER NAVAJO SERVICE MANUAL
Revised: 9/23/80
3C9
FUEL SYSTEM