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John Deere 4840 Troubleshooting

The John Deere 4840 is a two-wheel drive row-crop tractor from Iron Horses series. This model was manufactured between 1978 and 1982. The JD 4840 driveline components: John Deere 6466 four-stroke six-cylinder direct injection turbocharged intercooled diesel engine and 8x4 full powershift transmission.

A 466 cubic inches (7.6 L) engine has a cylinder bore of 4.56" (116 mm), piston stroke of 4.75" (121 mm), and rated power of 200 hp (148.1 kW). The maximum travel speed (forward and reverse): 18.6 mph (29.9 km/h) / 6.4 mph (10.3 km/h).

The closed center hydraulic system used a pump with a flow of 23 gpm (87.1 lpm) gpm. The hydraulic pressure is 157 bar (2275 psi). The John Deere 4840 was equipped with a power steering system, differential hydraulic wet disc brakes, 11.00x16 or 16.5Lx16.1 front tires, and 18.4x38 or 18.4x42 rear tires. The wheelbase is 118.5 inches (3000 mm).

Engine Troubleshooting
Engine hard starting or not starting
Plugged fuel filter - Clean or change the filter
Closed fuel supply valve - Open supply valve to inject fuel
There is air in the fuel system - Bleed the system
Fuel injectors are clogged or faulty - Test fuel injectors and change if necessary
Fuel injection pump failure - Install a new pump or rebuild
Bad cylinder compression - Inspect cylinder block and replace worn components
Engine stops running unexpectedly
Low coolant temperature - Warm up engine as required
There is air in the fuel system - Bleed the system
Bad fuel injection - Check and adjust
Fuel filter plugging - Change filter element
Fuel injectors are damaged or dirty - Clean or replace fuel injectors
Engine starts but immediately shuts off
Fuel injection pump out of timing - Correct injection timing
Dirty fuel filter element - Service or replace the filter
Faulty fuel injector nozzles - Service or replace injector nozzles
Fuel injection pump is not working correctly - Install a new fuel pump or repair
Dirty air cleaner element - Replace or service air cleaner element
Engine stops at idle
Wrong adjustment of low idle speed - Test and adjust
Fuel injection pump is defective - Rebuild or replace pump
Fuel injector nozzles fault - Service or replace injector nozzles
Valve clearance is not correct - Have it adjusted
Engine overheating
Insufficient coolant fluid - Top up coolant fluid. Check the components of cooling system
Cooling system parts are defective or system is dirty - Replace faulty parts or service cooling system
Lack of engine oil - Fill the crankcase with engine oil
Broken fan belt or incorrect belt tension - Replace or adjust belt tension properly
Defective thermostat - Test thermostat opening temperature, replace as required
Reduced engine power
Clogged or damaged injectors - Change fuel injectors
Incorrect fuel injection pressure - Repair or replace injection pump
Clogged air filter - Clean or replace the air filter element
Clogged oil filter - Change or clean engine oil filter element
Engine is overloaded - Load reducing required
Excessive valve clearance - Correct valve clearance
Incorrect low idle setting - Adjustment required
Fuel pipes or hoses are dirty - Clean fuel pipes and hoses
Engine losing compression: Valves are broken or leaking - Have valves replaced
Engine knocks or noises
Timing of fuel injection pump is not adjusted - Check and correct adjustments
Fuel injector nozzles are damaged or dirty - Change or clean injector nozzles
Engine oil level is low - Fill up the oil to required level
Engine has not warmed up to the recommended temperature - Warm up to required temperature
Main bearings or crankshaft are worn out - Have bearings or crankshaft replaced
Piston rings are damaged or broken - Have piston rings replaced
Flywheel mounting screws are loose - Tighten the screws
Diesel engine using too much oil
Oil leaking: Worn seals or gaskets - To repair leaks, replace worn parts
Crankcase oil too light - Use oil of correct viscosity
Stuck or defective piston rings - Piston rings replacement required
Damaged valve stems or valve guides - Valves must be replaced
Damaged cylinder liners or pistons - Inspect pistons and liners, replace as required

Electrical System Troubleshooting
Battery cannot be charged
Worn-out battery - Install a new battery
Damaged battery electrical wire harness - Inspect electrical wires for damage, change or repair
Loose or corroded battery cables and terminals - Tighten or clean terminals and cables
Defective belt or improperly adjusted belt tension - Adjust belt tension properly or replace belt
Starter turns slow
Battery capacity is low - Battery is drained, recharge it
Battery discharges quickly - Service or replace the battery
Damaged battery cable harness - Check electrical cables for damage, repair or replace
Loose or corroded cables and terminals - Tighten or service cables and terminals
Starter motor won't turn
Battery voltage is low - Low battery charging, charge as required
Drained or worn battery - Need to charge or replace the battery
Starter motor failing - Starter needs to be replaced
Wiring is improperly connected or disconnected - Need to reconnect the wiring properly

Transmission Troubleshooting
Hard shifts
Clutch is unadjusted or worn - Replace or adjust clutch
Damaged or loose gear shift linkage - Service or replace shift linkage
Worn or damaged shift forks - Replace defective shift forks
Gearshift mechanism is worn out - Repair or replace worn components if required
Low transmission oil pressure
Not enough fluid in transmission - Fill system with correct transmission fluid level
Dirty transmission oil filter (if fitted) - Replace or service transmission oil filter
Relief valve sticking - Replace valve as required
Transmission is making noise
Bearings are worn or damaged - Bearings replacement required
Lack of transmission fluid supply - Check and refill the transmission fluid
Dirty transmission fluid - Fill up with fresh transmission fluid
Gears are defective or backlash is incorrect - Change the gears or adjust backlash correctly
Bent or worn shift forks - Replace defective shift forks
External oil leaks
Broken gaskets or seals - Seals and gaskets replacement required
Cracked transmission housing - Housing needs to be replaced

Hydraulics Troubleshooting
Hydraulic system overheating
Hydraulic system pressure is unadjusted - Adjust the pressure as required
Faulty or incorrectly adjusted main relief valve - Adjust or replace the relief valve
Contaminated hydraulic fluid - Change hydraulic fluid
Air leaks in hydraulic system - Inspect the suction line, pump seals, and fittings
Hydraulic fluid pressure is low
Lack of hydraulic fluid - Need to add fluid
Hydraulic oil filter element clogging - Replace hydraulic filter element or service if necessary
Hydraulic pump is faulty - Check the pump capacity and replace pump if required
Damaged or incorrect adjusted hydraulic control valve - Change or set correctly
Defective hydraulic cylinder - Inspect cylinder components for wear or damage and change if required
Hydraulic lines are leaking - Find leaks in hydraulic system and repair it
3-point hitch does not raise or raises very slowly
Not enough hydraulic fluid in the system - Check and refill the hydraulic fluid
Cold hydraulic fluid - Warm up the fluid
Hydraulic oil filter clogging - Hydraulic filter maintenance required
Defective hydraulic pump - Test the pump performance and change pump if required
Main relief valve incorrect adjustment or failure - Adjust the valve or replace if necessary
Hydraulic spool valve is not set properly or defective - Replace or adjust properly
Hydraulic cylinder is faulty - Inspect the hydraulic cylinder parts for damage or wear and replace if required
Loose or damaged suction line - Tighten or replace
Hitch not dropping or hitch drops slowly
Faulty or incorrect setting hydraulic control valve - Replace or adjust properly
Defective hydraulic cylinder - Check the hydraulic cylinder parts for damage or wear and replace if necessary
Hitch cross shaft is damaged - Replace the shaft
Hitch has mechanical defects - Change defective or worn hitch parts
Hitch raises or lowers not smoothly
Air leaks in hydraulic system - Inspect the pump seals, suction pipe, and fittings
Dirty hydraulic fluid - The fluid must be changed
Hydraulic pump not working - Check hydraulic pump flow and replace pump if necessary
Hydraulic spool valve is not set properly or defective - Set correctly or replace
Hydraulic cylinder is faulty - Inspect the hydraulic cylinder parts for damage or wear and replace if required

Steering System Troubleshooting
Steering wheel is difficult to turn
Steering column is defective or improperly assembled - Change steering column or assemble properly
Air enters in steering system - Bleed air from system
Improper toe-in adjustment - Check toe-in and correct
Incorrect tire pressure - Inflate the tires correctly
Faulty steering pump - Repair or change steering pump
Worn or defective steering valve assembly - Check and replace as required
Stuck or worn relief valve - Flush relief valve or change if necessary
Steering fluid level is low - Check fluid level and add steering fluid as required
Steering system oil leakage - Tighten joints of hydraulic pipes and hoses in steering system
Excessive steering wheel free play
Steering column shaft or coupling is worn out - Change defective part
Steering valve assembly is worn or defective - Inspect and replace as required
Defective hydraulic steering pump - Install a new steering pump
Worn or faulty steering linkage or tie-rod ends - Change damaged part
Tractor is pulling to left or right
Deflated front tyres - Inflate tyres as needed
Toe-in adjustment is incorrect - Check and adjust toe-in
Steering tie-rod ends or linkage are defective - Replace failed part
Steering valve assembly is defective or worn - Replace or repair steering valve as required
Incorrectly adjusted or damaged front hub bearings - Adjust properly or replace bearings




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MF 250 MF 690 MF 3060 MF 6180
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