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Kubota M120 Troubleshooting

The Kubota M120 utility tractor was manufactured between 1998 and 2004. This model was designed in 2 versions: M120 (2WD) and M120DT (4WD). The Kubota M120 tractor is powered by Kubota F5802 4-cycle 5-cylinder direct injection turbocharged diesel engine. A 356 cubic inches (5.8L) engine has a cylinder bore of 4.29" (109 mm), piston stroke of 4.92" (125 mm), and rated power of 120 hp (89.5 kW).

The Kubota M120 is fitted with two transmission options: Powershift transmission with 16 forward and 16 reverse gears, and Powershift Creeper transmission with 24 forward and 24 reverse gears. Max forward/reverse speed (travel and creeper) - 20.3 mph (32.7 km/h) and 0.7 mph (1.2 km/h). The open center hydraulic system used a gear pump with a rated fluid flow of 20.6 gallons per minute (78 liters per minute). The rear lift capacity is 5200 lbs (2360 kg) at lift pin.

The 2WD models are equipped with 11.00-16 front tyres and 18.4-38 rear tyres. The 14.9-24 front tyres and 18.4-38 rear tyres fit 4WD tractors. The wheelbase is 103.7" (2630 mm) for models with 2-wheel drive and 105.9" (2680 mm) for models with 4-wheel drive. The tractor is compatible with a Kubota LA1301 loader with lift capacity to max height of 2865 lbs (1300 kg), or Kubota LA1601 loader with lift capacity to max height of 3527 lbs (1600 kg).

Engine Troubleshooting
Diesel won't start or hard to start
Fuel filter plugging - Service the filter
Fuel is not supplied from the tank to the system - Check the fuel shut-off valve
Fuel-line is leaking air - Retighten clamps, replace defective pipes
Clogged or damaged injectors - Check fuel injectors and replace if required
Fuel injection pump is broken - Replace injection pump or repair it
Poor cylinder compression - Check cylinder block and replace defective parts
Engine stops running while driving
Low coolant temperature - Warm up the engine
Fuel lines leaking air - Tighten clamps, change faulty pipes
Uneven fuel injections - Repair or adjustment
Dirty fuel filter element - Clean or change the filter
Faulty or dirty injectors - Clean or replace fuel injectors
Engine starts but immediately stops
Incorrectly set fuel injection pump timing - Adjust injection timing
Fuel filter is clogged - Clean or change the filter
Fuel injector nozzles are dirty or defective - Install new set of properly balanced nozzles
Fuel injection pump damage - Install a new pump or rebuild
Dirty air cleaner element - Air cleaner maintenance required
Engine stalling at idle
Incorrectly adjusted low idle speed - Correct the settings
Fuel injection pump is defective - Repair or change injection pump
Fuel injector nozzles are dirty or defective - Install a new set of well-balanced nozzles
Incorrect valve clearance - Need to adjust valve clearance
Engine overheats
Insufficient coolant - Fill cooling system to proper level. Inspect the system for leaks
Cooling system components are worn or system is clogged - Change faulty components or service cooling system
Lack of engine oil - Fill up the engine oil
Fan belt tension is improper or belt is damaged - Adjust as required or replace belt
Defective or wrong type of thermostat - Check thermostat, replace if necessary
Lack of engine power
Faulty or dirty injectors - Change fuel injectors
Incorrect fuel injection pressure - Adjust to correct pressure
Air filter clogging - Replace filter or install new filter element
Dirty oil filter element - Replace or service engine oil filter
Engine is overloaded - Reduce the load or operate the tractor in lower gears
Improper valve clearance - Adjust valve clearance
Incorrect low idle speed adjustment - Correct low idle adjustment
Fuel pipes or hoses clogging - Clean fuel pipes and hoses
Engine losing compression: Valves are faulty or leaking - Valve replacement required
Engine knocks or noises
Fuel injection pump out of timing - Correct injection timing
Fuel injector nozzles are defective or dirty - Change or clean injector nozzles
Engine oil level is insufficient - Add oil to the engine crankcase
Engine is not fully warmed up - Warm up engine as required
Worn crankshaft or main bearings - Install new parts
Piston rings are worn or broken - Have piston rings replaced
Loose flywheel bolts - Inspect flywheel bolts and tighten properly
Excessive oil consumption
Oil leakage: Seals or gaskets are defective - To repair leaks, replace worn parts
Incorrect oil viscosity - Use proper viscosity oil
Worn or broken piston rings - Have piston rings replaced
Valve guides and stems are worn - Change the valves
Pistons or cylinder liners are damaged - Inspect liners and pistons, fit new parts as necessary

Electrical System Troubleshooting
Battery won’t charge
Battery bad cell - Change the battery
Battery cable harness damage - Check battery cables for damage, change or repair
Loose or corroded cables and terminals - Tighten or clean cables and terminals
Damaged belt or incorrectly adjusted belt tension - Change belt or adjust belt tension properly
Starter turns slow
Battery power is low - Low battery charging, charge as required
Battery runs out quickly - Battery needs to be serviced or replaced
Battery wiring harness failure - Inspect electrical cables for defects, repair or replace
Loose or corroded terminals and cables - Tighten or clean cables and terminals
Starter does not work
Low battery output - Recharge the battery
Drained or worn battery - Replace or charge as required
Starter motor failure - Starter needs to be changed
Wiring harness is disconnected or improperly connected - Check wiring harness and reconnect properly

Transmission Troubleshooting
Gear hard to shift
Clutch is not adjusted or faulty - Adjust or change the clutch
Gear shift linkage is loose or broken - Service or replace shift linkage
Worn or damaged shift forks - Install new shift forks
Defective gearshift mechanism - Replace defective components
Transmission fluid pressure is insufficient
Oil level is low - Add transmission oil as required
Plugged transmission fluid filter (if equipped) - Replace or clean transmission fluid filter
Faulty relief valve - Replace valve as required
Transmission noises
Cracked or worn bearings - Replace faulty bearings
Not enough oil in transmission - Checking transmission oil level and add if necessary
Contaminated transmission fluid - Change transmission fluid
Incorrect backlash or gears are defective - Change the gears or adjust backlash correctly
Shift forks are damaged or worn - Change the shift forks
Transmission oil leakage
Broken gaskets or seals - Seals and gaskets replacement required
Cracked transmission case - Install a new transmission case

Hydraulics Troubleshooting
Hydraulic system overheating
Improper hydraulic pressure adjustments - Adjust it correctly
Main relief valve is faulty or misadjusted - Adjust or replace the relief valve
Hydraulic oil is contaminated - Fill up with fresh hydraulic oil
Air leaks in hydraulic system - Inspect the suction line, pump seals, and fittings
Insufficient hydraulic oil pressure
Hydraulic oil level is low - Check oil level and add hydraulic oil as required
Hydraulic oil filter clogging - Clean or replace the hydraulic filter
Defective hydraulic pump - Flow-rate hydraulic pump and replace pump if necessary
Hydraulic control valve block is defective or set improper - Replace or set correctly
Faulty hydraulic cylinder - Inspect the hydraulic cylinder components for damage or wear and change if required
Leakage in hydraulic pipes - Detect leaks in the system and fix it
Hitch fails to lift or lifts slowly
Hydraulic oil level is insufficient - Check oil level and add hydraulic oil as required
Cold oil in hydraulic system - Wait for oil to warm up
Hydraulic fluid filter clogging - Hydraulic filter maintenance required
Hydraulic pump is defective - Flow-rate hydraulic pump and replace pump if necessary
Main relief valve is damaged or adjusted improperly - Adjust or replace the relief valve
Defective or not adjusted hydraulic control valve - Adjust correctly or replace
Hydraulic cylinder is not working - Inspect cylinder components for damage or wear and change if required
Broken or loose suction line - Retighten or change
3-point hitch drops slowly or won't drop
Defective or not adjusted hydraulic spool valve - Adjust properly or change
Defective hydraulic cylinder - Check cylinder components for wear or damage and change if necessary
Worn hitch rock shaft - Change the shaft
The hitch is defective if there is internal mechanical damage - Replace worn or faulty hitch components
Hitch lowering or lifting is not smoothly
Aeration in hydraulic system - Check the pump seals, suction line, and fittings
Contaminated hydraulic oil - Change hydraulic oil
Defective hydraulic pump - Test pump flow rate and replace pump if required
Hydraulic spool valve block is faulty or out of adjustment - Change or adjust correctly
Hydraulic cylinder is faulty - Check cylinder parts for wear or damage and replace if necessary

Steering System Troubleshooting
Excessive effort to steer
Worn or improperly mounted steering column - Mount the steering column properly or change it
Air trapped in the steering system - Bleed the steering system
Improper toe-in adjustment - Check toe-in and correct
Tire pressure is low - Tires need to be inflated
Steering pump failure - Install a new hydraulic steering pump
Worn or defective power steering control valve - Inspect and change as required
Faulty steering box components - Change defective steering box parts
Steering oil level low - Add oil to steering system
Oil leaks in the steering system - Retighten steering hose and line connections
Excessive free play of steering wheel
Worn steering column shaft or coupling - Change defective part
Power steering control valve is defective or worn - Repair or replace the steering valve
Damaged steering box components - Repair power steering box
Steering pump is faulty - Replace or repair steering pump
Steering linkage or tie-rod ends are worn - Change damaged part
Front wheels wander to right or left
Tires are incorrectly inflated - Inflate as required
Incorrect toe-in adjustment - Check and adjust toe-in
Faulty or worn steering linkage or tie-rod ends - Replace damaged component
Faulty steering box parts - Defective power steering box components must be replaced
Faulty or worn power steering control valve - Repair or change the steering valve
Front hub bearings are worn or incorrectly adjusted - Replace the bearings or adjust it properly



Farm Tractors Technical Specifications
JD 1026R JD 3650 JD 6400 JD 7810
FORD 1320 FORD 2810 FORD 3930 FORD 5600
MF 250 MF 690 MF 3060 MF 6180
NH TC48DA NH M100 NH T7550 NH 8560
CASE IH 495 CASE IH 1255XL CASE IH 2140 CASE IH 2294