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John Deere 6620 Troubleshooting

The John Deere 6620 Premium is a 6020 series 4x4 utility tractor. This model was manufactured from 2001 to 2006. The John Deere 6620 tractor is powered by 414.4 cubic inches John Deere 6068T 4V-CR 4-stroke 6-cylinder turbocharged diesel engine with a maximum power of 130 Hp (96.9 kilowatt) and 535 Nm (396 lb-ft) of peak torque at 1700 rpm.

The John Deere 6620 Premium is equipped with 3 types of transmission. Type 1: 24x24 PowrQuad Plus partial powershift transmission. Type 2: 24x24 AutoQuad transmission.

Type 3: AutoPowr variable transmission (IVT) with infinite forward and reverse gears. Maximum travel speed (forward and reverse): 25 mph (40 km/h). The closed center hydraulic system with load-sensing control has an axial-piston or gear-driven pump with a rated capacity of 25.4 gpm (96.1 lpm). The main relief pressure is 300 bar (2900 psi). The John Deere 6620 Premium is fitted with 420/70R28 front tires and 18.4R38 rear tires. The wheel base is 104.3" (2640 mm). The tractor is compatible with a John Deere 661 loader with a maximum lift height of 166 (4220), or John Deere 731 loader with a lift capacity at full height of 4255 lb (1930 kg).

Engine Troubleshooting
Engine doesn't start or difficult to start
Fuel filter is dirty - Service or replace the filter
No fuel supply from the tank - Open the fuel supply valve
Air in fuel system - Air-bleed fuel system
Dirty or faulty injectors - Check fuel injectors and replace if required
Fuel injection pump damage - Replace or repair injection pump
Low engine compression - Inspect and replace faulty parts
Engine stops running while driving
Engine is not preheated - Warm up the engine
Air in fuel lines - Bleed fuel lines
Improper fuel injection - Fuel injection settings required
Dirty fuel filter element - Clean the filter or install new filter element
Dirty or faulty injectors - Check fuel injectors and replace if required
Engine starts and then stalls
Unadjusted fuel injection pump timing - Correct injection timing
Fuel filter is dirty - Clean the filter element
Fuel injector nozzles fault - Replace fuel injector nozzles
Fuel injection pump is defective - Install a new fuel pump or repair
Clogged air cleaner - Install new cleaner element or replace it
Engine shuts off while idling
Low idle speed setting is not correct - Need to adjust idle speed
Fuel injection pump is defective - Repair or install new pump
Fuel injector nozzles are dirty - Inspect injector nozzles and change if required
Excessive valve clearance - Have it adjusted
Engine overheated
Insufficient coolant fluid - Add the coolant. Inspect the system for leaks
Cooling system components are defective or system is dirty - Flush cooling system or change faulty components
Engine oil insufficient - Add oil to the engine crankcase
Fan belt is broken or belt tension is unadjusted - Adjust belt tension correctly or change it
Thermostat fault - Test thermostat opening temperature, replace as required
Loss of engine power
Clogged fuel injectors - Test fuel injectors and change if necessary
Incorrect fuel injection pressure - Adjust to correct pressure
Clogged air filter element - Install new filter element or replace it
Engine oil filter is plugged - Service or change engine oil filter element
Diesel engine overloaded - Reduce the load or use a lower gear
Incorrect valve clearance - Have it adjusted
Improperly adjusted low idle speed - Adjust the low idle speed
Fuel pipes or hoses clogging - Clean fuel pipes and hoses
Poor engine compression: Valves are damaged or leaking - Have valves replaced
Engine knocking sound or abnormal noise
Timing of fuel injection pump is wrong - Fuel injection pump timing adjustment needs to be corrected
Fuel injector nozzles are clogged or faulty - Change or clean injector nozzles
Lack of engine oil - Add oil to the engine crankcase
Engine has not warmed up to the recommended temperature - Warm up engine as required
Crankshaft or main bearings wear - Install new parts
Damaged or defective piston rings - Install new piston rings
Flywheel bolts are loose - Bolts need to be tightened
Excessive engine oil consumption
External oil leaks: Worn seals or gaskets - Change to repair leaks
Incorrect oil viscosity - Fill up with the correct oil viscosity
Worn or broken piston rings - Piston rings need to be replaced
Worn valve guides and valve stems - Change the valves
Cylinder liners or pistons are worn - Inspect pistons and liners, replace as required

Electrical System Troubleshooting
Battery will not charge
Battery bad cell - Battery replacement required
Battery electrical wire harness failure - Inspect wires for defects, change or repair
Battery cables and terminals are corroded or loose - Cables and terminals must be tightened or cleaned
Belt wear or improper belt tension adjustment - Install new belt or adjust belt tension as required
Starter cranks slowly
Low battery output - Low battery charging, charge as required
Battery does not hold charge - Service charging system or change battery
Bad battery wiring harness - Inspect wiring for malfunctions, replace or repair
Loose or corroded battery terminals and cables - Tighten or service cables and terminals
Starter will not crank
Battery power is low - Battery is drained, charge it
Discharged or faulty battery - Charge or change the battery
Starter motor failure - Repair or replace starter
Wiring harness is disconnected or improperly connected - Check wiring harness and reconnect properly

Transmission Troubleshooting
Gear shift is hard
Worn or misadjusted clutch - Change or adjust clutch
Gear shift linkage is stuck or worn - Service or replace shift linkage
Worn or damaged shift forks - Replace the shift forks
Gearshift mechanism is worn out - Repair or replace worn components if required
Insufficient transmission fluid pressure
Lack of transmission fluid supply - Fill up the transmission fluid
Transmission oil filter element is clogged (if equipped) - Replace or service transmission oil filter
Relief valve failure - Replace the valve
Transmission is excessively noisy
Broken or worn bearings - Faulty bearings should be changed
Not enough fluid in transmission - Fill the transmission housing with fluid
Transmission fluid contamination - Change transmission fluid
Gears are defective or backlash is incorrect - Change worn gears or set backlash correctly
Worn or damaged shift forks - Change defective shift forks
Transmission fluid leakage
Seals or gaskets are damaged - Gaskets or seal need to be replaced
Transmission housing is cracked - Replace housing or transmission assembly

IVT Transmission Troubleshooting
Transmission makes noise
Insufficient transmission fluid level or contaminated fluid - Add the fluid to proper level or pour fresh fluid
Damaged or not adjusted speed control rod linkage - Replace rod linkage or adjust correctly
Damaged relief valve - Change relief valve
Excessive loading - Reduce loading
Defective or worn components of IVT transmission - Inspect transmission components and replace if necessary
Transmission oil overheated
Not enough oil in transmission - Correct the transmission oil level
Plugged transmission fluid filter - Change or service the transmission fluid filter
Cooling components are plugged or defective - Check all cooling components and change or clean if required
Transmission overload - Load needs to be reduced
Lack of power
Fluid level is low - Add transmission fluid as required
Insufficient charge pressure - Test charge pressure
Defective or worn relief valve - Install a new valve
Transmission fluid leaking
Gaskets or seals are broken - Install new components
High pressure inside the transmission housing - Change or repair damaged parts
Oil return tube is plugged - Check tube and clean if required

Hydraulics Troubleshooting
Hydraulic system overheats
Hydraulic system pressure is not set correctly - Set the hydraulic pressure as required
Unadjusted or defective main relief valve - Adjust or replace the relief valve
Contaminated hydraulic fluid - Change hydraulic fluid
Air leaks in hydraulic system - Check the pump seals, suction pipe, and fittings
Low hydraulic system pressure
Not enough hydraulic fluid in the system - Need to add fluid
Hydraulic oil filter element clogging - Clean the hydraulic filter or install new filter element
Hydraulic pump is faulty - Test pump performance and replace pump if necessary
Hydraulic control valve block is not set properly or defective - Adjust correctly or replace
Broken hydraulic cylinder - Check the hydraulic cylinder parts for damage or wear and replace if necessary
Hydraulic piping leaks - Find leaks in the system and fix it
Hitch cannot be raised or raising is too slowly
Not enough hydraulic oil in the system - Fill the hydraulic system with oil
Hydraulic fluid is too cold - Allow fluid to warm
Hydraulic oil filter is dirty - Service the hydraulic filter or change if required
Hydraulic pump is defective - Check pump flow and install new pump if necessary
Faulty or incorrectly adjusted main relief valve - Adjust or change relief valve
Defective or not adjusted hydraulic control valve - Adjust correctly or replace
Hydraulic cylinder is faulty - Check cylinder components for damage or wear and change if necessary
Suction pipe is broken or loose - Tighten the pipe or replace it
Hitch won't lower or lowers slowly
Hydraulic control valve block is not set properly or defective - Adjust properly or change
Hydraulic cylinder is defective - Check cylinder components for wear or damage and change if necessary
Worn hitch cross shaft - Install a new shaft
The hitch has mechanical faults - Change worn or defective hitch parts
Hitch jerks when drop or lift
Air enters in hydraulic system - Inspect the pump seals, suction pipe, and fittings
Hydraulic fluid is dirty - Hydraulic fluid change required
Hydraulic pump failure - Check hydraulic pump flow and replace pump if necessary
Hydraulic control valve is not set properly or defective - Adjust properly or change
Hydraulic cylinder failure - Check cylinder components for damage or wear and change if necessary

Steering System Troubleshooting
Steering wheel turns hard
Damaged or improperly installed steering column - Reinstall or replace the steering column
Air trapped in the steering system - Bleed the steering system
Not adjusted toe-in - Check toe-in and correct
Incorrect tire pressure - Inflate the tires correctly
Steering pump not working - Install a new steering pump
Hydrostatic steering unit has wear or damage - Inspect and replace as required
Not enough steering fluid - Fill up steering fluid to required level
Steering system has oil leaks - Tighten the steering hose and pipe joints
Steering wheel has too much free-play
Worn steering column coupling or shaft - Replace defective part
Hydrostatic steering unit is defective or worn - Change or repair steering unit if required
Steering pump failure - Check the hydraulic steering pump and change if necessary
Steering linkage or tie-rod ends are defective - Change damaged part
Front wheels wander to right or left
Tires are improperly inflated - Inflate as necessary
Toe-in adjustment is incorrect - Adjust toe-in properly
Faulty or worn steering linkage or tie-rod ends - Change damaged part
Damaged or worn hydrostatic steering unit - Change or repair steering unit if required
Steering cylinder malfunction - Change or repair steering cylinder
Worn or incorrectly adjusted or worn front hub bearings - Adjust correctly or change bearings




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