Home / Farm Tractors / Kubota Tractors / Kubota L3901

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
Engine is overheated
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
Engine loses power
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
Starter motor turns slow
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
Starter is not cranking
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
External fluid leaks
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



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