JCB 8018 Mini Excavator Auxiliary Hydraulics Inoperative Diagnostic

Symptoms

• No hydraulic movement or sound from coupled attach devices
• No drop in engine RPM when moving auxiliary activation controls
• Stiff or stuck floor pedal pivot controls on mechanical models
• Slow, un-powered, or asymmetrical flow paths on the dual circuit

Possible Causes

• Rigidly seized floor control pedal pivot linkage or mechanical wire cable
• Failed auxiliary solenoid control relay or coil core block
• Mis-aligned auxiliary changeover selector valve (directing flow back to tank)
• Internal physical damage to third auxiliary circuit pump section

Diagnostic Procedure

1. 1
   Inspect Foot Pedal Pivot Linkage

   Physically inspect the floor mounted auxiliary pedal assembly. Excess dirt, rust, structural frame flexing, or trapped pebbles under metal plates often prevent physical linkage stroke. Spray link junctions with heavy fluid lubricant and verify mechanical motion.
2. 2
   Locate Auxiliary Circuit Selector Valve

   Trace auxiliary lines to the auxiliary selector block. Ensure selector block lever is switched fully to double-acting status. Pin positions out of place direct flow pathways immediately straight to the oil reservoir, stopping auxiliary flow.
3. 3
   Complete Electrical Relay Switch Tests

   On solenoid-actuated models, locate the auxiliary switch relay in the console. Monitor power flow to auxiliary line coils as the lever button is pressed down. Check wire insulation for physical abrasions where the cabin floor plate clamps.
4. 4
   Measure System Relief Pressure on Aux Outlets

   Install a 0-250 bar pressure gauge with adapter fittings directly to the machine's steel hydraulic quick-coupler outlets. Start engine and stroke auxiliary control. Confirm pressure peaks near specification level (typically 180 bar).

Common Repairs

• Cleaning, replacing, or re-pinning floor foot pivot linkage sets
• Repositioning the auxiliary selector block valve to two-way state
• Replacing failing solenoid coils on main relief pilot block units

Safety Precautions

• Uncouple all hydraulic attachments prior to safety test cycles
• Wear heavy structural gloves to check hydraulic couplings; escaping jet fluid is hazardous
• Ensure all pressure is completely bled down before disconnecting quick couplings

Required Tools

• 0-250 bar hydraulic pressure testing kit
• High quality penetrant rust spray bottle
• All-purpose mechanics socket wrench set
• Digital Multimeter (DMM)

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