9-33. ASSEMBLY OF FUEL PUMP. (Refer to Figure 9-7.)
raising and lowering the plunger in the tube. It should move fully without any tendency to stick. If a click cannot
be heard, the interrupter assembly is not functioning properly in which case the pump should be replaced.
b. Install the plunger spring cup gasket (use a new one) and the plunger spring cup. Draw the screws
reasonably tight, but do not over tighten them. Be sure the cup is not cocked to prevent the plunger from binding
in the tube.
c. Place the filter screen around the bottom cover magnet.
d. Carefully guide the screen around the plunger spring cup. The screen must fit snugly at both ends. Do not
pinch or distort the screen. Draw the bottom cover tight with a wrench and safety.
9-34. 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 electrical lead of the pump to a 14-volt DC power source.
c. Using a suitable container with the proper octane fuel, connect a fuel line from a container to the inlet side
of the pump.
d. Connect another line from the outlet side of the pump to a pressure gauge and by-pass valve and back to
the container.
e. Run the pump with the by-pass valve open until a steady flow of fuel is obtained. Then close the by-pass
valve and check the pressure gauge for the proper reading of 4 to 4.75 psi maximum, no flow.
f. Repeat steps b through e for the second fuel pump.
g. If the proper pressure is not obtained, the plunger spring may be replaced or it may be necessary to replace
the complete pump assembly.
9-35. ADJUSTMENT OF ELECTRIC FUEL PUMP (IN AIRPLANE).
a. With the access panel 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 by-pass valve and pressure gauge to the outlet end of the pump to be checked.
c. Place a container below the pump to catch any fuel from the test line during the adjustment of the pump.
d. Disconnect the electrical lead to the pump that is not being checked.
e. Turn the fuel selector on, open the by-pass valve on the test line and start the pump.
f. When a steady flow of fuel is obtained, close the by-pass valve and check the reading on the pressure
gauge. It should read 4 to 4.75 psi maximum, no flow. Do not keep by-pass valve closed for more than one
minute during pump operation and adjustment.
g. Repeat steps b through f for the other pump.
h. If the proper pressure is not obtained, the plunger spring may be replaced or it may be necessary to replace
the complete pump assembly.
i. Reconnect the original fuel line to the pump. Open fuel selector and run the pump to check for any fuel
leaks.
j. Shut off the pump, close the fuel selector and replace and secure the access panel.
PIPER AIRCRAFT
PA-28-161 CADET
AIRPLANE MAINTENANCE MANUAL
Issued: FEBRUARY. 28, 1989
FUEL SYSTEM
2A22
