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Kubota L3901 Troubleshooting
The
Kubota L3901 is a compact utility tractor from Standard L series. This model was
manufactured between 2014 and 2021. The tractor was designed in 2 versions:
L3901F (2-wheel drive) or L3901DT (4-wheel drive).
The Kubota L3901 powerline system components: a 111.4 cu.in (1.8L)
Kubota D1803-CR-E4 3-cylinder direct injection liquid-cooled diesel
engine with a rated power of 37.5 hp (28.1 kW), and synchronized shuttle
transmission with 8 forward and 8 reverse gears. The maximum travel
speed (forward/reverse): 13.2 mph (21.2 km/h) and 13.1 mph (21.1 km/h).
The open center hydraulic system includes a gear pump with a flow rate
of 6.3 gal/min (23.9 l/min). The hydraulic pressure is 162 bar (2350
psi). The 2WD models are equipped with 5.00x15 front tires and 11.2x24
rear tires. The 7.2x16 or 27x8.50-15 front tires and 11.2x24 or 15x19.5
rear tires are used for 4WD tractors. The wheelbase is 63.3 inches (1610
mm). Compatible attachments for the tractor: a
Kubota LA525 front-end
loader with lift capacity to full height of 1131 lbs (513 kg), and
Kubota BH77 backhoe with 2-ft flat digging depth of 89.8 inches (2280
mm).
Engine Troubleshooting |
Engine won't start or starts hard |
Fuel filter clogging - Service or replace the filter |
Closed fuel supply valve - Open supply valve to inject fuel |
Air in fuel system - Air-bleed fuel system |
Dirty or faulty injectors - Inspect fuel injectors and replace if necessary |
Fuel injection pump is not operating properly - Install a new pump or rebuild |
Poor cylinder compression - Check and change damaged parts |
Engine shuts off unexpectedly during operation |
Engine is cold - Warm up the engine |
Fuel lines leaking air - Tighten clamps, change faulty pipes |
Uneven fuel injections - Repair or adjustment |
Dirty fuel filter element - Change filter element |
Clogged fuel injectors - Service or change fuel injectors |
Diesel starts and then stalls |
Fuel injection pump out of timing - Check the fuel injection pump timing setting |
Dirty fuel filter element - Clean the filter or install new filter element |
Fuel injector nozzles are damaged or dirty - Replace fuel injector nozzles |
Fuel injection pump malfunction - Repair or install a new fuel pump |
Air cleaner element is dirty - Change or replace air cleaner element |
Engine stalls when idling |
Low idle speed adjustment is incorrect - Adjust low idling as recommended |
Fuel injection pump is faulty - Repair or replace injection pump |
Damaged or clogged injector nozzles - Change or clean injector nozzles |
The valve clearance is incorrect - Correct valve clearance |
Low engine coolant - Top up coolant fluid. Any leaks must be repaired |
Cooling system is clogged or cooling parts are defective - Service the cooling system or change faulty parts |
Lack of engine oil - Fill up the oil to required level |
Worn fan belt or incorrect belt tension - Adjust properly or replace the belt |
Defective or wrong type of thermostat - Check thermostat, replace if necessary |
Fuel injectors are clogged or faulty - Change fuel injectors |
Improper fuel injection pressure - Adjust to correct pressure |
Air filter element is dirty - Clean or replace the air filter element |
Oil filter is dirty - Service or replace engine oil filter |
Engine is running overloaded - Load reducing required |
Valve clearance is out of adjustment - Adjust valve clearance according to specifications |
Incorrect low idle speed adjustment - Correct low idle settings |
Dirt in the hoses or pipes - Fuel pipes and hoses need to be cleaned |
Insufficient engine compression: Leaking or faulty valves - Install new valves |
Abnormal engine noise or knocking |
Fuel injection pump out of timing - Adjust injection timing |
Fuel injector nozzles are defective or dirty - Replace fuel injector nozzles |
Engine oil level low - Add oil to the engine crankcase |
Engine is cold - Warm up the engine to required temperature |
Crankshaft or main bearings are worn out - Install new parts |
Piston rings are worn or broken - Replace piston rings |
Loose flywheel screws - Inspect the flywheel screws and tighten securely |
High engine oil consumption |
Oil leakage: Gaskets or seals are excessively worn - New components need to be installed |
Oil viscosity is wrong - Use proper viscosity oil |
Worn or broken piston rings - Have piston rings replaced |
Valve guides or stems are damaged - Replace the valves |
Cylinder liners or pistons are scuffed - Inspect liners and pistons, fit new parts as necessary |
Electrical System Troubleshooting |
Battery won’t charge |
Defective battery - Install a new battery |
Bad battery wiring harness - Inspect wiring for malfunctions, replace or repair |
Loose or corroded terminals and cables - Terminals and cables need to be tightened or cleaned |
Belt slipping or wrong belt tension adjustment - Adjust belt tension as required or change belt |
Low battery output voltage - Battery is drained, recharge it |
Battery is draining quickly - Service battery or replace it |
Bad battery electrical wire harness - Check wires for malfunctions, repair or replace |
Corroded or loose terminals and cables - Service or tighten battery terminals and cables |
Low battery voltage - Battery needs to be recharged |
Drained or faulty battery - Need to charge or replace the battery |
Starter motor failure - Replace or repair starter |
Disconnected or incorrectly connected cables - Need to reconnect cables correctly |
Transmission Troubleshooting |
Gear shift is hard |
Failure or improper clutch adjustment - Adjust clutch or change if necessary |
Damaged or loose gear shift linkage - Replace or repair the shift linkage |
Worn or damaged shift forks - Install new shift forks |
Gearshift mechanism failure - Change or repair failed components |
Low transmission pressure |
Oil level is low - Checking transmission oil level and add if necessary |
Transmission oil filter element is dirty (if fitted) - Replace or service transmission oil filter |
Relief valve sticking - Change the valve |
Excessive transmission noise |
Bearings are worn or cracked - Install new bearings |
Insufficient oil supply - Fill the transmission housing to proper oil level |
Transmission oil contamination - Change transmission oil |
Gears are defective or backlash is incorrect - Set backlash correctly or change the gears |
Worn or damaged shift forks - Shift forks need to be changed |
Gaskets or seals are damaged - Replace worn seal or gaskets |
Cracked transmission case - Install a new transmission case |
Hydraulics Troubleshooting |
Hydraulic system overheated |
Hydraulic system pressure is incorrect - Hydraulic pressure needs to be set correctly |
Misadjusted or defective main relief valve - Adjust the valve or replace if necessary |
Hydraulic oil is dirty - Hydraulic oil change required |
Air leaks in hydraulic system - Check the suction pipe, fittings, and pump seals |
Insufficient hydraulic fluid pressure |
Lack of hydraulic fluid - Need to add fluid |
Hydraulic fluid filter is clogged - Clean the hydraulic filter element or replace if necessary |
Hydraulic pump is faulty - Test pump performance and replace pump if necessary |
Faulty or incorrect setting hydraulic control valve - Change or adjust correctly |
Faulty hydraulic cylinder - Inspect the hydraulic cylinder parts for damage or wear and replace if required |
Leakage in hydraulic lines - Detect leaks in hydraulic system and repair it |
3-point hitch does not raise or raises very slowly |
Hydraulic fluid level is low - Add fluid to the hydraulic system |
Hydraulic oil is too cold - Allow oil to warm |
Hydraulic fluid filter element is dirty - Hydraulic filter maintenance required |
Damaged hydraulic oil pump - Test the pump performance and change pump if required |
Defective or misadjusted main relief valve - Adjust the valve or replace if necessary |
Hydraulic control valve is defective or set improper - Adjust properly or change |
Broken hydraulic cylinder - Check the hydraulic cylinder parts for damage or wear and replace if necessary |
Damaged or loose suction line - Tighten or change |
Hitch not dropping or hitch drops slowly |
Hydraulic control valve block is defective or set improper - Set correctly or replace |
Hydraulic cylinder is faulty - Inspect cylinder components for damage or wear and change if required |
Damaged hitch rock shaft - Install a new shaft |
Defective mechanical parts of the hitch - Replace defective or worn hitch parts |
Hitch jerks when lower or lift |
Air enters in hydraulic system - Check the suction line, pump seals, and fittings |
Dirty hydraulic fluid - The fluid must be changed |
Hydraulic pump failure - Test the pump performance and change pump if required |
Hydraulic spool valve block is not set properly or defective - Replace or adjust correctly |
Faulty hydraulic cylinder - Inspect the hydraulic cylinder parts for damage or wear and replace if required |
Steering System Troubleshooting |
Heavy steering |
Steering column is worn or incorrectly mounted - Change the steering column or mount it correctly |
Aeration in steering system - Air-bleed steering system |
Improper toe-in - Adjust toe-in correctly |
Low tire pressure - Inflate the tires |
Steering pump stopped working - Repair or change steering pump |
Defective or worn steering valve - Check and replace as required |
Worn power steering box parts - Repair power steering gearbox |
Insufficient steering oil - Need to add steering oil |
Steering system has oil leaks - Retighten joints of the hydraulic steering pipes and hoses |
Steering wheel has too much free-play |
Steering column coupling or shaft is worn - Change defective part |
Worn or damaged steering valve - Check and replace as required |
Damaged power steering box parts - Change defective steering box parts |
Steering pump stopped working - Check the hydraulic steering pump and change if necessary |
Steering linkage or tie-rod ends are defective - Replace failed part |
Tractor pulls to right or left |
Tires are deflated - Need to inflate tires |
Incorrect toe-in adjustment - Check and adjust toe-in |
Faulty or worn steering tie-rod ends or linkage - Change failed component |
Faulty power steering box parts - Change defective steering box parts |
Damaged or worn steering valve - Inspect and replace as required |
Front hub bearings are damaged or incorrectly adjusted - Adjust correctly or replace bearings |
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Farm Tractors Technical Specifications |