Home / Farm Tractors / Kubota Tractors / Kubota L3901HST

Kubota L3901HST Troubleshooting

The Kubota L3901HST is a 4-wheel drive compact utility tractor. This model was manufactured between 2014 and 2021. The Kubota L3901HST driveline includes a 111.4 cubic inches (1.8 L) Kubota D1803-CR-E4 4-cycle 3-cylinder direct injection naturally aspirated liquid-cooled diesel engine with a rated power of 37.5 hp (28.1 kW), and 3-range hydrostatic transmission with infinite forward and reverse gears.

Max travel speed (forward/reverse): 3.9 mph (6.3 km/h) using low range or 14.1 mph (27.2 km/h) using high range, and 3.5 mph (5.6 km/h) using low range or 12.7 mph (20.5 km/h) using high range.

The open center hydraulic system includes a gear pump with fluid flow rate of 6.3 gpm (23.9 lpm). The main relief pressure is 162 bar (2350 psi). The Kubota L3901HST is equipped with an integral power steering system, wet disc brakes, 7.2x16 (AG) or 27x8.50-15 (Industrial) front tires, and 11.2x24 (AG) or 15x19.5 (Industrial) rear tires. The wheel base is 63.3" (1610 mm). The tractor is compatible with 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" (2280 mm).

Engine Troubleshooting
Engine doesn't start or starts hard
Fuel filter is clogged - Clean or change the filter
Fuel is not supplied from the tank to the system - Check the fuel shut-off valve
Water, dirt, or air in fuel system - Drain, flush, fill, and bleed system
Fuel injectors are damaged or dirty - Check fuel injectors and replace if required
Fuel injection pump is damaged - Change pump or rebuild it
Bad engine compression - Inspect cylinder block and change worn parts
Diesel stalls while running
Engine has not warmed up to the recommended temperature - Warm up engine as required
Air trapped in fuel system - Bleed air
Improper fuel injection - Fuel injection settings required
Fuel filter is clogged - Change filter element
Fuel injectors are clogged or faulty - Change fuel injectors
Engine starts but immediately stops
Fuel injection pump timing is incorrect - Repair or replace fuel injection pump
Fuel filter is clogged - Service the filter
Clogged or damaged injector nozzles - Replace fuel injector nozzles
Fuel injection pump damage - Change or repair the pump
Air cleaner element is clogged - Change or replace air cleaner element
Engine stops when idling
Low idle speed setting is not correct - Adjust low idle speed
Fuel injection pump malfunction - Rebuild or change fuel pump
Fuel injector nozzles are dirty - Inspect injector nozzles and change if required
Valve out of adjustment - Check and adjust
Engine overheats
Insufficient coolant fluid - Fill the radiator to the required level. If there are leaks in the system, replace worn components
Cooling system is clogged or cooling parts are defective - Change faulty components or service cooling system
Engine oil level is insufficient - Fill up the engine oil
Broken fan belt or unadjusted belt tension - Adjust as required or change belt
Defective thermostat - Thermostat needs to be replaced
Lack of engine power
Clogged fuel injectors - Check fuel injectors and replace if required
Incorrect fuel injection pressure - Repair or replace injection pump
Air filter is dirty - Air filter maintenance required
Dirty oil filter - Service or change engine oil filter element
Engine overloaded - Reduce load on the engine
Improper valve clearance - Have it adjusted
Improperly adjusted low idle speed - Correct the settings
Dirt in the fuel pipes or hoses - Service fuel hoses and pipes
Engine compression too low: Worn or damaged valves - Have valves replaced
Engine knocks or noises
Timing of fuel injection pump is wrong - Check and correct adjustments
Fuel injector nozzles are dirty - Change or clean injector nozzles
Lack of engine oil - Check and refill engine oil
Engine is not preheated - Warm up the engine as required
Crankshaft or main bearings failure - Need to install new components
Piston rings are worn or broken - Replace piston rings
Loose flywheel screws - Check the flywheel screws and tighten as required
High oil consumption
Oil leakage: Seals or gaskets are defective - Replace worn parts to avoid leaks
Improper oil viscosity - Use proper viscosity oil
Piston rings are stuck or broken - Piston rings replacement required
Valve stems and guides are worn - Install new valves
Damaged pistons or cylinder liners - Inspect liners and pistons, change as necessary

Electrical System Troubleshooting
Battery cannot be charged
Battery is defective - Use a new battery
Bad battery electrical wire harness - Check wires for malfunctions, repair or replace
Battery terminals and cables are corroded or loose - Cables and terminals must be tightened or cleaned
Belt is defective or belt tension is improperly adjusted Adjust belt tension as required or replace belt
Starter turning slow
Low battery output - Charge the battery
Battery discharges quickly - Service charging system or install new battery
Battery cable harness damage - Check battery cables for damage, change or repair
Corroded or loose battery cables and terminals - Cables and terminals must be tightened or cleaned
Starter does not work
Low battery power - Charge the battery
Drained or defective battery - Battery needs to be recharged or replaced
Faulty starter motor - Starter needs to be replaced
Wiring is improperly connected or disconnected - Need to reconnect the wiring properly

Hydrostatic Transmission Troubleshooting
Excessive HST transmission noise
Insufficient transmission fluid level or contaminated fluid - Add the fluid to proper level or pour fresh fluid
Speed control rod linkage is damaged or unadjusted - Change or adjust rod linkage
Relief valve sticking - Replace relief valve as required
Transmission is under excessive load - Load needs to be reduced
Transmission components are worn or damaged - Replace or repair worn components
Transmission oil over heats
Insufficient fluid supply - Add transmission fluid as required
Plugged transmission fluid filter - Change or clean the transmission fluid filter
Cooling components are plugged or defective - Inspect all cooling components and replace or repair if necessary
Transmission is under excessive load - Reduce the load is required
Power is insufficient
Not enough fluid in transmission - Fill the transmission housing with fluid
Low charge pressure - Test charge pressure
Relief valve is worn or defective - Replace relief valve as required
Transmission fluid leaking
Gaskets or seals are damaged - Replace worn gaskets or seal
High pressure inside the transmission case - Inspect transmission components for wear or damage and replace if necessary
Plugged transmission fluid return tube - Inspect tube and service if required

Hydraulics Troubleshooting
Excessive hydraulic system heat
Improper hydraulic pressure adjustments - Adjust it correctly
Defective or misadjusted main relief valve - Set up or change the relief valve
Hydraulic fluid is contaminated - Fill up with new hydraulic fluid
Air in hydraulic system - Check the suction line, pump seals, and fittings
Hydraulic fluid pressure is insufficient
Not enough hydraulic fluid in the system - Check and refill the hydraulic fluid
Dirty hydraulic oil filter - Change the hydraulic filter element or service if required
Hydraulic pump is defective - Check pump flow and change pump if necessary
Hydraulic control valve block is defective or set improper - Set properly or replace
Hydraulic cylinder is not working - Inspect cylinder parts for wear or damage and replace if required
Hydraulic pipes are leaking - Inspect hydraulic system for leaks and repair it
Hitch cannot be lifted or lifting is too slow
Not enough hydraulic fluid in the system - Fill the hydraulic system with oil
Hydraulic oil is too cold - Allow oil to warm
Dirty hydraulic oil filter - Install a new hydraulic filter element
Faulty hydraulic oil pump - Flow-rate pump and change pump if necessary
Main relief valve is faulty or misadjusted - Adjust or change relief valve
Defective or incorrect setting hydraulic control valve block - Replace or adjust correctly
Hydraulic cylinder is faulty - Inspect cylinder components for wear or damage and change if required
Suction pipe is broken or loose - Tighten the pipe or replace it
Hitch does not lower or lowers very slowly
Defective or not adjusted hydraulic spool valve - Replace or adjust properly
Hydraulic cylinder is not working - Inspect cylinder parts for wear or damage and replace if required
Worn hitch rock shaft - Install a new shaft
Damaged mechanical components of the hitch - Change defective or worn hitch components
Three-point hitch raises or lowers not smoothly
Air in hydraulic system - Check the pump seals, suction line, and fittings
Contaminated hydraulic oil - Change hydraulic oil
Damaged hydraulic oil pump - Check pump performance and change it if necessary
Hydraulic control valve is defective or set improper - Set correctly or replace
Faulty hydraulic cylinder - Check cylinder parts for wear or damage and replace if necessary

Steering System Troubleshooting
Excessive effort to steer
Steering column is damaged or incorrectly assembled - Steering column must be assembled correctly or changed
Air leaks in steering system - Air-bleed steering system
Incorrect toe-in adjustment - Check toe-in and correct
Tires are not correctly inflated - Inflate tires as necessary
Steering pump is faulty - Replace or repair steering pump
Worn or damaged steering valve - Replace or repair steering valve as required
Damaged steering box parts - Defective power steering box components must be replaced
Insufficient steering fluid - Fill up the steering fluid
Oil leaks in the steering system - Tighten the steering line and hose joints
Excessive free play of steering wheel
Steering column coupling or shaft has maximum wear - Change faulty component
Steering valve is defective or worn - Inspect and replace as required
Faulty steering box parts - Defective parts of power steering box must be replaced
Steering pump malfunction - Steering pump needs to be replaced or repaired
Faulty or worn steering linkage or tie-rod ends - Change damaged component
Tractor pulls to left or right
Deflated front tyres - Inflate tyres as needed
Improper toe-in - Check toe-in and correct
Worn or faulty steering linkage or tie-rod ends - Replace damaged component
Faulty steering box parts - Defective power steering box components must be replaced
Steering valve has wear or damage - Repair or change the steering valve
Damaged or improperly adjusted or worn front hub bearings - Change or adjust bearings correctly



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