Start the primary or backup hydraulic system and operate the rear
door switch in the UP and DOWN positions.
The pressure gage
should indicate at least 300 psi. If limited or no pressure is
indicated, replace or repair the hydraulic lines between the
actuator and directional control valve. If sufficient pressure
is indicated, replace the hydraulic actuator.
Assume that the
door opened and continue to troubleshoot the system.
o Close the dump valve.
Hold the upper rear door switch in the
DOWN position. Slowly open the dump valve (Fig. 51F). If the
door does not close shut, down the hydraulic system, install a
tee connector and pressure gage between the inlet and outlet
hoses, and troubleshoot as you did in the previous step. Assume
the door closed and close the dump valve, shut down the hydraulic
system, and continue troubleshooting the system.
o Disconnect the hydraulic actuator for the rear door and allow it
to hang from the ceiling. Remove the flow control valve and the
hydraulic line to the actuator tee connection. Install a jumper
hose between the pilot check valve and actuator tee connection,