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John Deere E120 Troubleshooting

The John Deere E120 lawn tractor was manufactured between 2018 and 2020. The John Deere E120 powertrain system components: a 40.1 (656 cc) Briggs and Stratton 40N877 Intek IC 4-cycle V-twin cylinder OHV air-cooled gasoline engine with a rated power of 20 hp (14.8 kW), and belt-driven hydrostatic transmission with infinite forward and reverse gears.

The engine has a float-feed carburetor, integral type fuel pump, full pressure lubrication system with spin-on oil filter, and forced air cooling system. Max forward speed - 5.5 mph (8.8 kph), maximum reverse speed - 3.2 mph (5.1 kph).

The lawn tractor is equipped with a manual steering system, wet disc brakes, 15x6.00-6 front tires, and 20x8.00-8 rear tires. The wheelbase is 49" (1240 mm). The John Deere E120 is compatible with the following attachments: a 42" mid-mount 2-blade mower deck with cutting height of 1.0-4.0" (25-102 mm), 13 cut positions, and manual lift system, 44" front-mount 2-stage snow blower, and 46" front blade.

Engine Troubleshooting
Engine will not start or difficult to start
No fuel in fuel tank - Fill gasoline up
Incorrect fuel grade - Change gasoline
There is air in the fuel system - Bleed the system
Spark plug wire is disconnected or loose - Check the spark plug wire connection, repair or replace
Spark plug is defective - Spark plug need to be replaced
Fuel filter is clogged - Fuel filter needs changing
Safety contact for brake pedal defective - Install new part
Wrong carburetor adjustment - Adjusting carburetor correctly
Low cylinder compression - Check cylinder block and replace worn parts
Choke cable is unadjusted or damaged - Adjust correctly or change the cable
Engine runs unevenly
Air intake screen is plugged - Wash or clean as required
Ignition system malfunction - Inspect ignition system and change failed components
Throttle cable is stuck or faulty - Clean or replace the cable
Clogged air filter - Service or change air filter
Dirty or faulty fuel pump - Inspect fuel pump and change as required
Engine starts and immediately shuts off
Spark plug is faulty - Replace spark plug
Carburetor is dirty or faulty - Clean or change carburetor
Ignition coil is not working - Replace ignition coil as necessary
Broken or bad valve springs - Valve springs need to be changed
Valves sticking - Valves need to be cleaned
Engine overheats
Engine oil level low - Check oil level and add oil as required
Engine overloaded - Load reducing required
Clogged cooling fins - Clean and wash as required
Carburetor mixture is too lean - Adjust carburetor correctly
Wrong ignition timing - Set the ignition timing properly
Valve setting is incorrect - Set the valves properly
Engine noises or knocks
Stale or low octane fuel - Change fuel
Engine is overloaded - Reduce the load
Engine oil level low - Fill the crankcase with engine oil
Low idle speed setting is not correct - Correct idle adjustment
Fuel pump is dirty or defective - Service or replace fuel pump
Crankshaft or main bearings failure - Replace crankshaft or bearings
Excessive valve clearance - Check and adjust
Piston rings or cylinder bore are damaged - Change faulty components
Lack of engine power
Improperly adjusted or dirty carburetor - Clean or properly adjust carburetor
Air filter element is clogged - Replace or service air filter
Fuel pump is dirty or defective - Service or replace fuel pump
Defective ignition - Inspect ignition system and change failed components
Cylinder head gasket is blown - Install new head gasket
Valves are stuck or burned - Clean or change valves
Push rod is worn or damaged - Push rod should be replaced
Worn cylinder block parts - Change defective parts
High fuel consumption
Choke did not open fully - Change or adjust choke cable
Incorrect adjustment of carburetor main jet - Adjust the carburetor main jet properly
Spark plug is faulty or loose - Re-tighten or replace spark plug
Worn, stuck, or burned valves - Service or change valves
Sleeve, piston, or rings are damaged - Replace defective components
Incorrect valve clearance - Adjust valve clearance
Engine consuming too much oil
Gaskets or seals are excessively worn - Replace worn parts to avoid leaks
Valve stems and guides are worn - Valves must be replaced
Worn or stuck piston rings - Have piston rings replaced
Piston or cylinder liner is scored - Check liner and piston, replace as required
Breather pipe or hose is clogged - Replace or service

Hydrostatic Transmission Troubleshooting
Hydrostatic transmission makes noise
Defective or not adjusted speed control pedal linkage - Change or adjust linkage
Transmission overload - The load should be reduced
Transmission oil is contaminated or oil level is insufficient - Add oil to proper level or pour fresh transmission oil
Defective or worn transmission parts - Check transmission parts for defect or damage and change if necessary
Shifting is hard
Rusty or worn shift linkage - Install a new gear linkage
Seized or worn hydrostatic pump - Repair or change pump
Misadjusted or faulty transmission shift control components - Adjust properly or change
Loss of power
Transmission fluid insufficient - Add fluid to the transmission housing
Worn or damaged drive sheave - Install a new sheave
Shifting linkage is misadjusted or broken - Adjust properly or change linkage
Speed control linkage is worn or unadjusted - Adjust or repair linkage
Transmission leaking
Broken transmission gaskets or seals - Change gaskets or seals
Final drive shaft is leaking - Shaft seals need to be changed
Transmission case is cracked - Replace case or transmission assembly

Mower Deck Troubleshooting
Excessive mower vibration
Mower deck drive pulley is worn or dirty - Clean or change pulley
Worn or loose drive belt - Belt needs to be adjusted or replaced
Mower blades are bent or out of balance - Change or balance blades
Loose blade bolts tightening - Bolts should be tightened
Discharge chute regular clogging
Mowing speed is too high - Select a lower speed
Grass is too long - Use a lower cutting height
Engine runs at low revs - Choke is not fully opening
Mower cuts too low - Change cutting height adjustment
Drive belt installation is not correct - Install drive belt as required
Uncut grass when mowing
Mower deck is clogged - Need to clean the mower deck
Blades are not sharp - Sharpen the blades
Worn or defective blades - Blades must be changed
High ground speed - Operate at slower speed
Mower deck set to low cutting - Use correct cutting height
Full bagger - Remove grass from bagger
Blades are scalping the grass
Lawn is uneven or bumpy - Level the lawn
Cutting level is too low - Raise the cutting height
Ground speed is too fast - Need to slow down
Incorrect level of mower deck - Level the deck correctly
Worn or bent blades - Blades need to be replaced
Low tire pressure - Inflate tires as required
Mower cuts uneven
Tires are not correctly inflated - Inflate tires as required
Improper mower deck level - Adjust the level of mower deck correctly
Excessive blade dullness - Blades need to be sharpened
Worn or defective blades - Replace the blades
Mower deck is clogged - Clean mower deck as required
Deck shell is damaged - Replace or repair the deck
Mower spindle is faulty or loose - Change or repair the spindle

Electrical Troubleshooting
Battery will not charge
Corroded or loose cable connections - Service or tighten connections
Battery terminal clamps are defective - Replace terminal clamps
Battery failing - Battery change required
Starter turns slowly
Battery capacity is low - Battery is drained, charge it
Battery won’t hold charge - Battery needs service or replacement
Disconnected wires or corroded battery terminals - Connect wiring properly or install new terminals
Starter is not working
Battery is discharged or defective - Change or recharge battery
Battery cables are disconnected or improperly connected - Inspect cables and connect properly
Battery voltage is low - Charge the battery
Faulty or incorrectly gapped spark plug - Replace or clean and gap
Solenoid or starter motor is faulty - Starter/solenoid needs to be replaced




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