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Kubota L4701HST Troubleshooting

The Kubota L4701HST is a 4WD compact utility tractor from Standard L-series. This model was manufactured between 2014 and 2021. The Kubota L4701HST powertrain system components: Kubota V2403-CR-E4 4-cycle vertical 4-cylinder direct injection naturally aspirated water-cooled diesel engine and 3-range hydrostatic transmission with infinite forward and reverse gears.

A 148.5 cubic inches (2.4L) engine has a cylinder bore of 3.43" (87 mm), piston stroke of 4.03" (102.4 mm), rated power of 47.3 hp (35.2 kW), and maximum torque of 146.2 Nm (107.8 lb-ft) at 1400 rpm. Max forward speed - 15.8 mph (25.4 kph), max reverse speed - 14.2 mph (22.9 kph). The open center hydraulic system used a gear pump with a flow of 7.8 gpm (29.5 lpm). The hydraulic system pressure is 177 bar (2560 psi).

The Kubota L4701HST is equipped with a hydrostatic power steering system, wet disc brakes, 8.3x16 front tires, and 14.9x24 rear tires. The wheel base is 72.6 inches (1845 mm). The tractor can be equipped with the following attachments: Kubota LA765 front-end loader with a maximum lift height of 105.2 inches (2670 mm), and Kubota BH92 backhoe with 2-ft flat digging depth of 106.1 inches (2690 mm).

Engine Troubleshooting
Engine will not start or hard to start
Clogged fuel filter element - Change filter element
Fuel shut-off valve closed - Open the fuel shut-off valve
Air in fuel pipes - Bleed fuel pipes
Clogged or damaged injectors - Change fuel injectors
Fuel injection pump failure - Rebuild or replace pump
Engine has bad compression - Check cylinder block and replace defective parts
Diesel shuts off during operation
Engine has not warmed up to required temperature - Normalize the engine temperature
Fuel lines leaking air - Tighten clamps, change faulty pipes
Irregular fuel injection - Adjust fuel injection timing
Dirty fuel filter element - Change filter element
Dirty or damaged injectors - Check fuel injectors and replace if required
Engine starts and immediately stops
Unadjusted fuel injection pump timing - Fuel pump timing settings need to be corrected
Dirty fuel filter element - Change filter element
Clogged or damaged injector nozzles - Service or replace injector nozzles
Fuel injection pump is not operating properly - Install a new fuel pump or repair
Air cleaner element is clogged - Service or change air cleaner
Engine stalls while idling
Too low idle RPM - Need to adjust idle speed
Fuel injection pump is faulty - Replace injection pump or repair it
Clogged or defective injector nozzles - Service or replace nozzles if required
Valve clearance is not correct - Adjust valve clearance
Engine overheated
Not enough coolant - Refill to the correct level. Check for coolant leaks
Cooling system parts are damaged or system is dirty - Service the cooling system or change faulty parts
Engine oil level low - Need to add engine oil
Fan belt tension is improper or belt is damaged - Adjust properly or change the belt
Defective or wrong type of thermostat - Check thermostat, replace if necessary
Reduced engine power
Fuel injectors are clogged or faulty - Test fuel injectors and change if necessary
Incorrect fuel injection pressure - Repair or replace injection pump
Air filter element clogging - Change or service air filter element
Engine oil filter is plugged - Replace or clean engine oil filter element
Diesel engine overloaded - Reduce the load or use a lower gear
Improper valve clearance - Adjust valve clearance
Incorrect low idle setting - Adjust low idle speed
Clogged fuel hoses or pipes - Clean fuel system hoses and pipes
Lack of compression: Valves are defective or worn - Valve replacement required
Engine noises or knocks
Incorrectly set fuel injection pump timing - Fuel pump timing settings need to be corrected
Fuel injector nozzles fault - Check and change nozzles as required
Low engine oil level - Check oil level and add oil as required
Engine is cold - Warm up the engine as required
Main bearings or crankshaft failure - Change or repair worn components
Piston rings are damaged or broken - Install new piston rings
Loose flywheel bolts - Check flywheel bolts and tighten properly
Diesel engine using too much oil
External oil leaks: Damaged seals or gaskets - Change to repair leaks
Incorrect oil viscosity - Use oil of correct viscosity
Worn or stuck piston rings - Change the piston rings as required
Worn valve stems and valve guides - Replace the valves
Pistons or cylinder liners are damaged - Inspect pistons and liners, fit new components as necessary

Electrical System Troubleshooting
Battery does not charge
Battery bad cell - Battery change required
Battery wiring harness failure - Inspect electrical cables for defects, repair or replace
Corroded or loose battery cables and terminals - Tighten or clean cables and terminals
Worn belt or improperly adjusted belt tension - Install new belt or adjust belt tension as required
Starter turning slow
Low battery voltage - Recharge the battery
Battery is not holding charge - Service charging system or change battery
Battery wiring harness damage - Inspect battery wiring for damage, replace or repair
Battery terminals and cables are loose or corroded - Tighten or service terminals and cables
Starter is not cranking
Battery capacity is low - Low battery charging, charge as required
Drained or worn battery - Change or recharge battery
Faulty starter motor - Starter needs to be replaced
Wiring harness is disconnected or improperly connected - Check wiring harness and reconnect properly

Hydrostatic Transmission Troubleshooting
HST transmission makes excessive noise
Low fluid level or contaminated fluid - Change the transmission fluid or fill to required level
Speed control rod linkage is damaged or unadjusted - Adjust or change rod linkage
Relief valve failure - Change the valve
Transmission overload - Reduce loading
Damaged or worn transmission parts - Replace or repair worn components
Transmission fluid over heats
Low transmission fluid level - Check and refill the transmission fluid
Clogged transmission fluid filter element - Clean or replace the transmission fluid filter
Cooling components are plugged or defective - Check all cooling components and repair or change if required
Excessive transmission load - Reduce loading
Power is too low
Low transmission fluid level - Fill up the transmission fluid
Charge pressure is too low - Test charge pressure
Defective or worn relief valve - Install a new valve
Transmission oil leaking
Gaskets or seals are defective Change defective gaskets or seal
High pressure inside the transmission case - Repair or replace worn parts
Clogged transmission fluid drain line - Service or replace drain line

Hydraulics Troubleshooting
Hydraulic system overheating
Hydraulic system pressure is not set correctly - Set the hydraulic pressure as required
Main relief valve is damaged or adjusted improperly - Replace or set up the relief valve
Contaminated hydraulic fluid - Change hydraulic fluid
Air enters in hydraulic system - Check the suction pipe, fittings, and pump seals
Low hydraulic system pressure
Not enough hydraulic oil in the system - Add oil to the hydraulic system
Hydraulic oil filter clogging - Change hydraulic filter element or clean if necessary
Defective hydraulic pump - Test the pump flow rate and install new pump if required
Hydraulic spool valve block is faulty or out of adjustment - Set properly or replace
Hydraulic cylinder is broken - Check cylinder parts for wear or damage and replace if necessary
Hydraulic piping leaks - Detect leaks in the system and fix it
3-point hitch lifts slowly or won't lift
Hydraulic oil level is insufficient - Add oil to the hydraulic system
Cold hydraulic oil - Warm up the oil
Hydraulic oil filter is dirty - Change hydraulic filter element or clean if necessary
Damaged hydraulic oil pump - Test pump flow rate and replace pump if required
Main relief valve is defective or unadjusted - Adjust or replace the relief valve
Hydraulic spool valve is faulty or out of adjustment - Adjust properly or change
Hydraulic cylinder is broken - Check cylinder parts for wear or damage and replace if necessary
Damaged or loose hydraulic suction line - Tighten or change it
3-point hitch won't drop or drops slowly
Hydraulic spool valve block is faulty or out of adjustment - Change or set correctly
Hydraulic cylinder malfunction - Inspect cylinder components for damage or wear and change if required
Hitch rock shaft is damaged - Install a new shaft
The hitch has any internal mechanical damage - Change faulty or worn hitch components
Hitch is lowered or raised jerkily
Hydraulic system sucks air - Check the pump seals, suction pipe, and fittings
Contaminated hydraulic oil - Change hydraulic oil
Defective hydraulic pump - Test the pump flow rate and change pump if required
Defective or incorrect setting hydraulic control valve block - Replace or adjust properly
Defective hydraulic cylinder - Inspect cylinder components for wear or damage and change if required

Steering System Troubleshooting
Steering is hard
Damaged or improperly fitted steering column - Fit the steering column properly or change it
Air leaks in steering system - Bleed the system of air
Toe-in adjustment is incorrect - Check toe-in and correct
Deflated front tyres - Inflate tyres as needed
Steering pump not working - Check the steering pump and replace if necessary
Hydrostatic steering unit is defective or worn - Repair or change the steering unit
Relief valve failure or seizing - Inspect relief valve and replace if necessary
Steering fluid level low - Checking steering fluid level and add it if necessary
Steering system oil leakage - Retighten steering line and hose connections
Steering wheel free play is excessive
Worn steering column coupling or shaft - Replace defective part
Damaged or worn hydrostatic steering unit - Change or repair steering unit if required
Steering pump is faulty - Check the steering pump and replace if necessary
Steering tie-rod ends or linkage are defective - Change damaged component
Front wheels wander to right or left
Tires are improperly inflated - Inflate as necessary
Improper toe-in adjustment - Adjust toe-in wheels properly
Faulty or worn steering linkage or tie-rod ends - Replace failed component
Worn or defective hydrostatic steering unit - Repair or replace the steering unit
Steering cylinder is worn - Replace or repair steering cylinder
Front hub bearings are improperly adjusted or defective - Adjust correctly or change bearings



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