TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Pressure above  Clogged case drain  Check applicable case drain  Clean or Replace 
normal (3100 psi)  return filter No. 1 and/or No. 2 engine-driven pump  filter for contamination High pressure indication occurs during operation of engine-driven pumps. Switch No. 1 and 2 hydraulic pump switches to OFF until pressure bleeds off to about 2000 psi. Switch No. 1 pump switch to ON and check indicator. If pressure indication does not rise above normal, pump No. 2 is defective. If pressure indication rises above normal with pump No. 2 switch OFF, switch pump No. 1 switch to OFF until pressure bleeds off to about 2000 psi. Switch No. 2 pump switch to ON and check indicator. If pressure indication does not rise above normal, pump No. 1 is defective. If pressure rises to above normal (3100 psi) on both of the above checks for No. 1 and No. 2 pumps, both pumps could be defective or the pressure transmitter or indicator could be defective. To isolate trouble, continue with the following tests for transmitter and indicator.  filter Ref 29-11-41 Replace No. 2 pump Replace No. 1 pump 
Pressure above  Restriction in the line  Check applicable pump lines  Remove, replace as 
normal (3100 psi)  or bent line  for flow check.  necessary. 

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TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Pressure above normal (3100 psi) (Cont.) Pressure below tolerance specified in par. 1.C.  System A pressure transmitter and/or indicator No. 1 and No. 2 engine-driven pumps System A pressure transmitter and/or indicator  Open ground interconnect valve and pressurize system A and B by turning on system B electric motor-driven pumps or by connecting a ground hydraulic service cart to the airplane ground power module. Compare system A and system B pressure indicator readings. If system B indicator reads normal pressure and system A still reads above normal, system A transmitter and/or indicator are defective If system A and B indicators both read normal, then both system A engine-driven pumps No. 1 and No. 2 are defective Low pressure indication occurs during operation of engine-driven pumps No. 1 and No. 2. Shut down engines, open ground interconnect valve and pressurize system A and B by turning on system B electric motor-driven pumps or by connecting a ground hydraulic service cart to the airplane ground power module. Compare system A and system B pressure indicator readings  Test system A transmitter and indicator. Refer to 29-31-0, Pressure Indicating Systems. Repair or replace as required. Replace No. 1 and 2 engine-driven pumps 

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TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Pressure below  System A pressure  If system B indicator reads  Test system A 
tolerance specified  transmitter and/or  normal and system A  transmitter and 
in par. 1.C. (Cont)  indicator (Cont) System A engine-driven pumps No. 1 and 2. System A pressure relief valve Hydraulic leaks  indicator still reads below normal, then system A transmitter and/or indicator are defective.  If system A and B indicators both read normal, then both system A engine-driven pumps No. 1 and No. 2 are defective. If system A and B indicators both read below normal, close ground interconnect valve. If system B pressure indicator rises to normal, system A pressure relief valve is opening at too low pressure. With both systems A and B pressurized monitor system A fluid quantity indicator. If quantity indicator shows loss of fluid, open panels and trace hydraulic leakage to its source.  indicator. Refer to 29-31-0, Pressure Indicating Systems. Repair or replace as required. Replace engine-driven pumps No. 1 and No. 2. Replace pressure relief valve and recheck system A Repair or replace defective components 
Hydraulic fluid  Hydraulic leaks  Pressure systems A and B.  Repair or replace 
quantity low  Fluid quantity indicator and/or transmitter  Trace hydraulic fluid leakage to its source. Refer to 29-33-0, Hydraulic Fluid Quantity Indicating Systems -Trouble Shooting.  defective components 

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