Test Setup For Combustion Air Blower Switch - Piper Navajo PA-31 Service Manual

Figure 13-26. Test Setup for Combustion Air Blower Switch
2.
Immerse the fuel feed and nozzle holder assembly in clean water with the fuel inlet and
nozzle cavity left open.
3.
Observe for bubbles which would indicate leakage. If bubbles appear at either fuel fitting,
there is a leak in the fuel tube. If bubbles appear externally on the shroud tube, or at either end of the
shroud tube juncture, the shroud tube is leaking.
4.
In either of the above cases, the complete fuel feed and nozzle holder assembly must be
replaced.
f.
Spray test the nozzle as follows:
1.
Install the nozzle in the nozzle holder assembly which contains a fuel solenoid or on later
heaters route lines through the solenoid to a 7 psi fuel pressure source.
2.
Connect the solenoid leads to a 24-volt battery. Connect a switch in the line to open and
close the solenoid when desired.
3.
With the switch closed (solenoid valve energized) observe the fuel spray pattern. It should be
conical in shape with even dispersion in all directions.
WARNING
Be sure to keep the atomized spray away from fire.
4.
Energize and de-energize the solenoid several times. The spray should shut off permanently
each time the solenoid is de-energized. There should be no sign of dribbling at the nozzle tip in excess of
one or two drops.
5.
If the spray pattern is distorted, check for an obstruction and clean the nozzle as described
in Paragraph 13-44, Step i. If this fails to provide a normal spray pattern, replace the nozzle.
6.
If the nozzle continues to dribble, the solenoid valve is not closing properly and the fuel
feed and nozzle holder assembly must be replaced on 39D59 heaters or the solenoid assembly must be
replaced on B39D59 heaters.
Reissued: 10/12/79
HEATING AND VENTILATING SYSTEM
PIPER NAVAJO SERVICE MANUAL
5C16