Piper Navajo PA-31 Service Manual page 582

PIPER NAVAJO SERVICE MANUAL
Left and right fuel flow warning lights, standard on PA-31-325 and PA-31-310 with
serial numbers 31-7512013 and up, are mounted at the base of the windshield divider post
and will illuminate to warn the pilot of an impending fuel flow interruption. Each light is
controlled by a sensing probe mounted near each inboard fuel tank outlet. In the event the
fuel level near the tank outlet drops to a point where a fuel flow interruption and power loss
could occur, the sensing probe will activate and energize the gated relay. This relay, located
aft of bulkhead station 81.00 and bolted to the windshield channel bracket, delays the
illumination of the warning light for 2 seconds. If after the 2 second delay the sensing probe
is still activated, the relay will then close the circuit to the warning light for a minimum of
10 seconds and will remain closed if the cause is not corrected. The lights are provided with
a "press-to-test" feature. To test, depress the button mounted in the center of the light
cluster for 3 seconds; the lights should illuminate and remain on for 10 seconds. During this
test, the fuel boost pump inoperative lights mounted below the fuel flow warning lights
should illuminate when the button is depressed (no hold required on this circuit) and go out
when the button is released.
9-2. TROUBLESHOOTING. Troubles peculiar to the fuel system are listed in Table IX-II
at the back of this section, along with their probable causes and suggested remedies. When
troubleshooting, check from the fuel supply to the items affected. If no trouble is found by
this method, the trouble probably exists inside individual pieces of equipment; they may
then be removed from the airplane and overhauled, or identical unit or units tested and
known to be good installed in their place. Troubleshooting the fuel quantity indicator may
be found in Section X, Instruments. The electrical system diagram for the system may be
found in Section XI, Electrical System.
Reissued: 10/12/79
FUEL SYSTEM
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