Piper COMANCHE PA-24-180 Service Manual page 510

PIPER COMANCHE SERVICE MANUAL
is pined.
b. Turn the fuel selector valve to the off position.
c. Disconnect fuel lines and electrical lead.
d. Remove the bolts securing the pump(s) and remove from aircraft. Do not allow dirt or for-
eign matter to enter the open fuel lines.
e. To install fuel pump(s), secure to the mounting bracket of the aircraft.
f. Check the fuel lines and pump(s) that no dirt has entered the fuel system. Connect the fuel
lines and electrical lead. Ascertain that each pump has a good ground.
g. Turn on the master switch, pump switch and open the line on the outside of the pump to
purge any air. Resecure the line and check for fuel leaks.
h. Operate the engine for a short time and then clean the inlet screen to the carburetor or
injector.
°-26. Fuel Pump, Bendix Plunger Type. (PA-24-180, PA-24-250 and PA-24-260 with carburetor
'duction.) These pumps are designed with a solenoid, which when energized activates a hollow
plunger. The plunger stroke is controlled by a set of interrupting points in the electrical circuit
and a calibrated plunger spring. The interrupter system is sealed in gas atmosphere. If any of
the electrical components become inoperative, the complete pump must be replaced.
Field service is limited to the extent of cleaning the bottom cover, filter screen, plunger
tube and plunger assembly. On the PA-24-180 and PA-24-250 aircraft, pump internal parts differ
with the early style(referto
figure 8-15) and the late style(refer to figure 8-16). On the PA-24-260
only the late style pump is used.
1. Early Plunger Pump. (Refer to Figure 8-15.)
a. To service the early pump, detach from the aircraft and remove the bottom cover (1) and
filter screen (4) as explained in paragraph 8-22.
b. Disassemble the plunger spring cup (8) by removing the three screws (3) securing the
cup. Gently touch the plastic cup valve (5) with your finger. If it is free, do not remove the valve
spring. Do not apply air pressure to this assembly. Use long nose pliers to replace valve as-
sembly if it falls out of the cup. It will click when the assembly is properly seated.
c. Pull the plunger spring (9) and plunger assembly (10) from the pump with your fingers.
Do not drop or mutilate the plunger. The buffer spring and valve (7) must nor be removed from the
plunger. Wash the plunger assembly in gasoline or a reliable solvent. If it does not wash clean
or if there are any rough spots, gently dress with crocus cloth.
d. Shake the plunger assembly and listen for click to indicate valve action. If valve is not
free, replace plunger assembly. Slosh the pump assembly in gasoline ox a solvent. Swab the tube
with a cloth wrapped stick and blow out with air pressure.
e. Reassemble the unit by inserting the plunger assembly in the tube with the buffer spring
end first. Check fit by slowly raising and lowering the plunger in the tube. It should move freely
without any tendency to stick. A click will be heard each time the plunger approaches the top of
tube. If the click cannot be heard, the interrupter assembly is not functioning properly. Replace
the pump. To finish the reassembly, install the plunger spring cup gasket (use a new one) and
the plunger spring cup. Draw the screws to a snug fit, but not over tight. Be sure the cuo :s not
cocked to prevent the plunger from binding in the tube.
f. Placethe filter screen around the bottom cover magnet, twist the cover with your fingers
and carefully guide the screen around the plunger spring cup. The screen must fit snugly at both
ends. Do nor pinch or disto-t the screen. Install the cover and safety. Install on aircraft and
FUEL SYSTEM
ISSUED: 8/18/72
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