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Kubota B7400 Troubleshooting

The Kubota B7400 is a 4-wheel drive compact utility tractor. This model was manufactured between 2000 and 2003. The Kubota B7400 tractor is powered by 43.9 cubic inches (0.7 L) Kubota D722-E 3-cylinder indirect injection naturally aspirated liquid cooled diesel engine with a maximum power of 16 Hp (11.9 kW) and 44.7 Nm (33 lb-ft) of peak torque at 2600 rpm.

The Kubota B7400 is fitted with 2 transmission options: gear shift transmission with 6 forward and 2 reverse gears, or 2-range hydrostatic transmission with infinite forward and reverse gears.

Max. travel speed (forward and reverse): 11.7 mph (18.8 km/h) / 7.3 mph (11.7 km/h). The open center hydraulic system used a single gear pump with a flow rate of 3.9 gpm (14.8 lpm). The tractor was equipped with a manual steering system, multi-plate wet disc brakes, 6.00x12 front tires, and 8.3x16 rear tires. The wheel base is 59 in (1490 mm).

Compatible attachments for the Kubota B7400 tractor: 54", 60" mid-mount 3-blade side discharge rotary mower decks with cutting height of 1.5-4.0 in (30-100 mm), and Kubota LA272 loader with lift capacity to max height of 685 lbs (310 kg).

Engine Troubleshooting
Diesel will not start or hard to start
Fuel filter is dirty - Change filter element
Fuel supply valve is closed - Open fuel supply valve
Fuel lines leaking air - Tighten clamps, change faulty pipes
Dirty or damaged injectors - Clean or replace fuel injectors
Faulty fuel injection pump - Replace or repair injection pump
Low compression - Check and replace worn parts
Engine stops unexpectedly while running
Engine is not warmed up to the required temperature - Warmed up the engine as required
Air in fuel system - Air-bleed fuel system
Fuel injection failed - Use correct settings
Fuel filter is clogged - Replace filter element
Clogged fuel injectors - Clean or replace fuel injectors
Diesel starts and immediately stops
Fuel injection pump timing is incorrect - Fuel injection pump timing adjustment needs to be corrected
Fuel filter clogging - Replace filter element
Fuel injector nozzles are clogged or faulty - Service or replace injector nozzles
Fuel injection pump malfunction - Install a new fuel pump or repair
Dirty air cleaner - Change or replace air cleaner element
Engine stalls at idle
Too low idle RPM - Need to adjust idle speed
Fuel injection pump is not operating properly - Change pump or rebuild it
Fuel injector nozzles are defective or dirty - Check and change nozzles as required
Valve clearance is not correct - Need to adjust valve clearance
Engine overheating
Lack of engine coolant - Top up coolant fluid. Inspect the system for leaks
Cooling system components are failed or system is dirty - Service the cooling system or replace faulty components
Engine oil level low - Fill the crankcase with engine oil
Fan belt is defective or belt tension is not adjusted - Adjust correctly or replace the belt
Defective thermostat - Check and replace if required
Poor engine power
Fuel injectors are defective or dirty - Clean or replace fuel injectors
Incorrect fuel injection pressure - Check the fuel injection pressure and adjust if necessary
Air filter clogging - Service or change air filter
Oil filter element clogged - Clean or change engine oil filter
Diesel engine overloaded - Reduce engine load
The valve clearance is not adjusted - Need to adjust valve clearance
Wrong adjustment of low idle speed - Correct low idle adjustment
Fuel hoses or pipes clogging - Clean fuel pipes and hoses
Low engine compression: Intake or exhaust valves are damaged - Replace the valves as required
Engine knocking or noise
Fuel injection pump out of timing - Check and correct settings
Fuel injector nozzles are defective or dirty - Check and change nozzles as required
Engine oil level is low - Fill up the oil to required level
Low coolant temperature - Engine is not warmed up to the required temperature
Crankshaft or main bearings are worn out - Replace crankshaft or bearings
Broken or worn piston rings - Have piston rings replaced
Flywheel screws are loose - Tighten the screws firmly
High oil consumption
Oil leaks: Gaskets or seals can be faulty - Change to repair leaks
Crankcase oil too light - Fill up with the correct oil viscosity
Piston rings are stuck or broken - Change piston rings
Valve stems or guides are damaged - Need to replace the valves
Scored pistons or cylinder liners - Inspect pistons and liners, replace as required

Electrical System Troubleshooting
Battery is not charging
Faulty cell in battery - Battery replacement required
Battery wiring harness damage - Inspect battery wiring for damage, replace or repair
Corroded or loose terminals and cables - Service or tighten battery cables and terminals
Belt damage or incorrect belt tension adjustment - Adjust belt tension correctly or change belt
Starter turning slow
Battery power is low - Recharge the battery
Battery won’t hold charge - Battery needs service or replacement
Bad battery electrical wire harness - Check wires for malfunctions, repair or replace
Battery cables and terminals are loose or corroded - Cables and terminals must be tightened or cleaned
Starter will not crank
Low battery power - Recharge the battery
Drained or faulty battery - Recharge or replace battery
Starter motor is damaged - Starter needs to be changed
Disconnected or incorrectly connected wiring harness - Inspect wiring harness and reconnect it as required

Hydrostatic Transmission Troubleshooting
HST transmission makes noise
Oil level is insufficient or oil is contaminated - Top up to proper level or change oil
Damaged or not adjusted speed control rod linkage - Repair or adjust link rod linkage
Relief valve failure - Replace relief valve
Transmission is under excessive load - Reduce transmission load
Worn or damaged parts of the hydrostatic transmission - Change or repair damaged parts
Transmission fluid overheated
Oil level is low - Checking transmission oil level and add if necessary
Transmission fluid filter is dirty - Replace or clean transmission fluid filter
Cooling components are clogged or damaged - Inspect all cooling components and service or replace if necessary
Excessive loading - The load should be reduced
Power is too low
Oil level is low - Correct the transmission oil level
Low charge pressure - Test charge pressure
Relief valve is worn or defective - Install a new valve
Transmission oil leaking
Broken gaskets or seals - Install new gaskets or seal
High pressure inside the transmission case - Replace or repair defective components
Clogged oil return tube - Service or replace return tube

Hydraulics Troubleshooting
Hydraulic system overheats
The system pressure has not been corrected - Make the correct settings
Defective or misadjusted main relief valve - Replace or set up the relief valve
Dirty hydraulic fluid - The fluid must be changed
Hydraulic system sucks air - Inspect the suction line, pump seals, and fittings
Hydraulic fluid pressure is insufficient
Lack of hydraulic fluid - Fill the hydraulic system with oil
Hydraulic oil filter element is dirty - Replace filter element or clean if required
Hydraulic pump is defective - Test the pump performance and change pump if required
Defective or incorrect setting hydraulic control valve block - Set properly or replace
Hydraulic cylinder is defective - Inspect the hydraulic cylinder parts for damage or wear and replace if required
Leakage in hydraulic lines - Identify leaks in the system and repair it
Three-point hitch lifting is too slow or cannot be lifted
Not enough hydraulic fluid in the system - Add fluid to the hydraulic system
Hydraulic fluid is too cold - Allow fluid to warm
Hydraulic oil filter element is dirty - Change hydraulic filter element or clean if necessary
Hydraulic pump failure - Check pump flow and install new pump if necessary
Main relief valve incorrect adjustment or failure - Adjust or change relief valve
Damaged or incorrect adjusted hydraulic spool valve - Adjust correctly or change
Hydraulic cylinder failure - Check the hydraulic cylinder parts for damage or wear and replace if necessary
Suction pipe is broken or loose - Tighten the pipe or replace it
3-point hitch fails to drop or drops slowly
Hydraulic spool valve is not set properly or defective - Adjust properly or change
Hydraulic cylinder is faulty - Check cylinder components for damage or wear and change if necessary
Lift arm shaft is damaged - Change the shaft
The hitch has internal mechanical malfunctions - Replace faulty or worn hitch parts
3-point hitch lift or lower is jerky
Air in hydraulic system - Check the suction line, pump seals, and fittings
Hydraulic fluid is dirty - Hydraulic fluid change required
Hydraulic pump is defective - Flow-rate hydraulic pump and replace pump if necessary
Faulty or incorrect setting hydraulic control valve - Adjust correctly or replace
Hydraulic cylinder is broken - Inspect cylinder parts for wear or damage and replace if required

Steering System Troubleshooting
Hard Steering
Steering knuckle or steering column is stuck - Inspect steering column and knuckle, replace worn parts
Steering gearbox components are worn - Replace defective components of steering gearbox
Faulty drag link or tie rod - Replace or repair
Insufficient lubrication in steering box - Need to lubricate the gearbox
Not adjusted toe-in alignment - Check and adjust toe-in
Tires are not correctly inflated - Inflate tires as necessary
Excessive steering wheel free play
Steering column bearing or shaft is worn - Change faulty parts
Steering linkage assembly is worn or loose - Repair or replace steering linkage
Worn steering gearbox bearings - Replace the bearings
Front wheel hub bearings or steering knuckles are worn - Change hub bearings or knuckles
Damaged or worn steering tie-rod ends - Change faulty part
Tractor pulls to right or left
Worn or loose steering linkage assembly - Repair or replace steering linkage
Defective steering knuckle bushing - Replace knuckle bushing
Uneven tire pressure - Inflate the tires properly
Toe-in adjustment is incorrect - Adjust toe-in correctly



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MF 250 MF 690 MF 3060 MF 6180
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