Bleeding the Fuel System

Maintenance of the M88A1
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Step 3. Install the new fuel filters hand tight. Then, use the fuel filter

wrench to further tighten the filters making sure the seals on top of the

filters are compressed between the top rim of the fuel filter and the

underneath of the filter cover to prevent leakage of fuel while the engine

is in operation.

Step 4. If still serviceable, install and tighten the screw and lockwasher

on the top cover of both air filters, and proceed to bleed the fuel system,

as described in the following subparagraph.

(3) Bleeding the Fuel System.

Whenever any type of maintenance or

repairs are performed on the fuel system, which permits air to enter the

system, such as replacing the filters, the air must be bled from the fuel

system.

The following steps provide the procedures for bleeding the APU

fuel system.

Step 1. Ensure that the FUEL SHUTOFF switch (2) (refer back to figure 29,

view A, on page 68) is in the OFF position before attempting to bleed and

prime the APU fuel system. Disconnect the fuel return line (1) and return

line fitting (2) (figure 33 on the following page).

Step 2.

Gently try to actuate the priming lever (3) to determine if the

pump lobe on the engine camshaft is in the up position.

If the priming

lever fails to move, the pump lobe is in the up position, thereby preventing

the movement of the priming lever (3) to bleed and prime the APU fuel

system. Crank the engine one revolution to move the pump lobe away from the

up position and to permit hand priming of the fuel system. If the priming

lever moves freely, do not crank the engine; but, prime the fuel system as

described in the next step.

Step 3. Hand operate the priming lever (3) (figure 33) on the fuel transfer

pump (4) until no air bubbles appear in the fuel flowing from the return

line fitting (2).

Step 4. Return the priming lever (3) (figure 33) to the disengaged position

to permit normal operation of the fuel transfer pump (4).