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Home / Wheel Loaders / Hitachi Wheel Loaders / Hitachi ZW120

Hitachi ZW120 Troubleshooting

The Hitachi ZW120 wheel loader driveline system components: Kubota V3800-TI-CRS 4-cycle vertical inline 4-cylinder direct injection turbocharged intercooled diesel engine with a rated power of 98 hp (73 kW), and 2-speed hydrostatic transmission. The open center hydraulic system has a gear pump with a rated capacity of 30.8 gal/min (117 l/min). The Hitachi ZW120 is equipped with a power steering system, hydraulic wet disc brakes, and 17.5x25 tires. The wheel loader has a maximum lift height of 140" (3555 mm) and bucket breakout force of 17730 lbs (8060 kg). The rated operating capacity is 6083 lbs (2765 kg), and tipping load is 12165 lbs (5530 kg).

Engine Troubleshooting

Engine starts up hard or will not start
Air in the fuel lines - Bleed the fuel lines.
Fuel filter element is clogged - Change the filter element.
Fuel injection nozzles are dirty or defective - Test injection nozzles and change if necessary.
Water in the fuel system - Change fuel and repair fuel system.
The valve clearance is not adjusted - Adjust to proper valve clearance.
Fuel injection pump is damaged - Rebuild or replace pump.

Engine starts but stalls suddenly
Air filter is clogged - Clean or change filter.
Fuel filter element is clogged - Change or clean the filter element.
Poor fuel injection pump tightness - Look for any leaks of fuel pump, tighten it fast.
Clogged or defective injectors - Inspect fuel injectors and change as required.
Fuel injection pump is damaged - Rebuild or replace pump.

Engine stops running suddenly
Engine is not fully warmed up - Warm up engine as required.
Fuel filter element is clogged - Change filter element.
Air in fuel system - Bleed fuel system.
Fuel injection nozzles fault - Replace injection nozzles.
Fuel injection pump timing is wrong - Adjust as recommended.

Engine stalls at idle
Incorrectly adjusted low idle speed - Adjust as required.
Fuel injection pump is broken - Repair or replace injection pump.
Damaged or clogged injectors - Replace fuel injectors.
Valve clearance is not correct - Check and adjust.

Loss of engine power
Air filter is plugged - Clean or change filter.
Fuel injection nozzles fault - Clean or change injection nozzles.
Fuel injection pressure is wrong - Adjust pressure to proper level.
Valve clearance is not correct - Adjust valve clearance.
Too low idle RPM - Adjustment required.
Restricted fuel hoses or lines - Clean fuel hoses and lines.
Worn cylinder head gasket - Replace the gasket as required.
Defective or worn piston rings - Replace piston rings.

Engine overheating
Low engine coolant - Add coolant fluid to cooling system and also check it for leaks.
Low engine oil level - Fill the crankcase with engine oil.
Damaged radiator cap or dirty radiator core - Install new cap or clean radiator.
Loose or defective fan belt - Install new fan belt.
Engine overloaded - Reduce load on the engine.

Oil pressure is low
Insufficient engine oil - Check and refill the oil.
Oil filter clogging - Service or change engine oil filter element.
Improper type of engine oil - Use oil of correct viscosity.
Crankshaft bearing oil clearance is incorrect - Install new bearings.
Oil pump is worn or damaged - Check and replace if necessary.

Engine noise or knocking
Engine oil level is low - Add oil to the engine crankcase.
Engine not warmed up - Normalize the temperature by warming up the engine.
Timing of fuel injection pump is incorrect - Set the fuel pump timing correctly.
Low idle speed setting is incorrect - Adjust low idle speed.
Fuel injectors are dirty or defective - Change or clean fuel injectors.
Connecting rod failure or misalignment - Connecting rod needs to be replaced or aligned.
Pistons are worn or broken - Pistons replacement required.

Hydrostatic Transmission Troubleshooting

Hydrostatic transmission is making noise
Contaminated transmission fluid or low fluid level - Top up to proper level or change transmission fluid.
Worn or unadjusted speed control linkage - Adjust or repair linkage.
Relief valve failure - Install a new relief valve.
Excessive transmission load - The load should be reduced.
Worn or defective transmission components - Replace or repair defective components.

Low power
Lack of transmission oil supply - Fill the transmission housing to proper oil level.
Relief valve malfunction - Replace the valve.
Speed control pedal linkage is bent or not adjusted - Change or adjust linkage.

Transmission fluid is too hot
Low oil level - Check and refill the transmission oil.
Plugged transmission oil filter - Service or replace the transmission oil filter.
Cooling components are plugged or defective - Check all cooling components and repair or change if required.
Transmission overloaded - Reduce transmission load.

External oil leaks
Seals or gaskets are worn - Install new components.
Transmission case internal pressure is too high - Check transmission parts for damage or wear and replace if required.
Oil drain line is clogged - Clean or change the line.

Hydraulics Troubleshooting

Hydraulic system overheats
Incorrect hydraulic pressure setting - Hydraulic pressure must be set correctly.
Main relief valve malfunction or improper adjustment - Adjust or replace the relief valve.
Hydraulic oil contamination - Change hydraulic oil.
Hydraulic fluid level is insufficient - Add fluid to the hydraulic system.
Worn hydraulic oil pump - Change or repair hydraulic pump if required.

Lift arm won't raise or lower
Damaged lift controls - Change or repair.
Hydraulic pump is broken - Change or repair hydraulic pump if required.
Hydraulic control valve malfunction - Repair or change hydraulic valve.
Hydraulic cylinder failure - Repair or install a new lift cylinder.
Hydraulic fluid is insufficient - Add fluid as required.

Bucket can't tilt
Bucket tilt controls are damaged - Inspect and repair if necessary.
Hydraulic pump is broken - Repair or change pump if required.
Hydraulic control valve malfunction - Repair or change hydraulic valve.
Bucket cylinder malfunction - Replace or repair cylinder.
Hydraulic fluid level low - Add fluid as required.

Slow boom or bucket operation
Hydraulic pump is faulty - Test pump flow rate and replace pump if required.
Hydraulic cylinder oil leakage - Install new cylinder seals.
Insufficient hydraulic oil - Checking hydraulic oil level and add if necessary.
Defective or not adjusted hydraulic control valve - Adjust properly or repair.
Hydraulic system loosing pressure - Adjust it correctly.

Jerky operation of the bucket or boom
Hydraulic system is leaking air - Need to bleed air.
Plugged hydraulic oil filter - Clean or change the filter.
Hydraulic fluid is dirty - Fill up with fresh hydraulic fluid.
Cylinder rod or tube is scratched - Change worn component.

Hydraulic pump makes excessive noise
Hydraulic system leaking or not enough oil - Remedy hydraulic leakage or refill oil as necessary.
Dirty hydraulic filter - Clean or change the filter.
Suction line clogging - Need to clean the suction line.
Pump sucks air - Air bleeding is required.
Pump components are worn out - Replace or rebuild the pump.

Electrical Troubleshooting

Battery does not charge
Loose or corroded electrical wiring connections - Clean or tighten wiring connections.
Faulty electrical terminal connectors - Change terminal connectors.
Dead cell in battery - Battery replacement required.
Loose or defective belt - Need to adjust belt tension or replace belt.

Starter cranks slowly
Battery capacity is low - Battery is drained, charge it.
Battery won’t hold charge - Battery needs service or replacement.
Bad battery terminals or disconnected wiring - Check wiring connections and replace or clean terminals.

Starter motor is not working
Battery is discharged or defective - Need to charge or replace the battery.
Disconnected or improperly connected wiring harness - Inspect battery wiring harness and connect as required.
Low battery output - Recharge the battery.
Starter motor failing - Change or repair starter.

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