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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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
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| Farm Tractors Technical Specifications |
