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