John Deere 317, 320, CT322 Operation and Test Manual — Wiring Diagrams

Check hydraulic oil level cold before you chase anything else. Tee a gauge into the charge circuit and run the engine at fast idle, 2930 to 3070 rpm per the engine specs on page 40. Charge pressure relief should hold 1900 kPa as listed on page 310. Low charge means a plugged filter or a worn charge pump.

Park level, load the bucket, and measure cylinder rod movement over one minute against the 12.7 mm maximum boom drift figure on page 29. Exceed that and the leak is internal, not electrical. Run the checkout procedure starting on page 22, then verify system relief holds 23 800 kPa (page 306) before you pull the loader valve.

Bleed the fuel system first and check for air drawn past the filter head seals. Set slow idle to 1230 to 1370 rpm and fast idle to 2930 to 3070 rpm using the procedures on page 40. If surge continues under load, verify turbocharger boost reaches 121 kPa at 2800 rpm on a 320 or CT322.

Back-probe the boom and bucket spool lock solenoids with an ohmmeter. Both Y2 and Y3 should read 14.8 to 18.2 ohms per the component specs on page 196, and the port lock solenoid Y4 reads 8.2 to 9.0 ohms. Out of range, replace the coil. In range, chase the seat switch circuit and connector pins.

Stop running the machine immediately. Cut the filter open and inspect the media for bronze or steel. Drain and flush the reservoir, replace every filter, and inspect both drive motors before restart. Confirm charge pressure returns to 1900 kPa (page 310) and system relief to 23 800 kPa once the circuit is clean.

Test brake release pressure at the port with the engine at fast idle. Release requires 1724 to 2068 kPa as specified on page 380. Below that, inspect the solenoid circuit and the supply line for restriction. Verify the park brake output code list on page 193 before you condemn the brake pack itself.