Specifications

Model 900 Trouble Shooting
Page M3
How to check hydraulic circuit and installation
Mount a flow meter in place of the hammer. Also, mount a low pressure (0-300 psi) gauge on the outlet of
the flow meter in order to test the back pressure in the return circuit.
With the flow meter in place, activate the circuit and bring the machine up to operating temperature. Do not
test the machine cold.
If the control valve is equipped with solenoid, switch on the solenoid before starting the engine to avoid
damage to the flow meter. Do not switch on or off the solenoid when the engine is running. Adjust the flow
output to match the requirements of the breaker (26 to 40 gpm).
After the flow has been adjusted, load the flow meter to the hammer operating pressure 1813 psi value plus
600 psi, If necessary, readjust the flow to keep the hammer flow value constant for pressure varying between
1000 psi and hammer operating pressure value (1813 psi) plus 600 psi.
Relief valve problems
If you cannot reach the proper oil flow at the hammer operating pressure value plus 600 psi, you may have a
bad system relief setting or a bad hammer control valve.
To check system relief valve see excavator manual for proper relief setting. Build pressure with the flow
meter to determine relief cracking pressure (usually 50 to 200 psi below relief setting). Reset relief if needed.
There should be 400 to 500 psi between hammer regulated pressure value and system cracking pressure or
heat may develop.
Pump problems
If you cannot produce proper oil flow against pressure varying from 1000 psi to hammer operating pressure
plus 600 psi, pump may be bad; assuming that relief valve is set properly.
Hammer control valve problems
If relief valve and pump are good, open and close valve three or four times. The valve spool may be sticking
or back pressure is developing on return line.
With the flow adjusted and the flow meter loaded to hammer operating pressure value plus 600 psi, take
note of the low pressure gauge reading.
The return pressure should be less than 150 psi. If the back pressure is more than 150 psi, the restriction
causing this higher pressure must be found and eliminated.
After the flow meter test is completed, disconnect the flow meter and connect the hoses to the hammer.
Mount a high pressure gauge (0-3000 psi) on the hammer HP line and take the machine outside. Run the
hammer on a heavy 3 inch by 40 inch by 40 inch steel plate on hard ground and take note of the pressure
reading. Call your TRAMAC dealer if pressure adjustments are needed.