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John Deere D120 Tractor Problems

Gasoline Engine Troubleshooting

John Deere D120 tractor engine starting problems

Empty gas tank - Fill it up.
Improper fuel grade - Change gasoline.
Stale gas - Drain fuel and replace with fresh fuel.
Fuel system clogged - Repair or replace.
Faulty spark plug wire - Inspect and replace if required.
Faulty spark plug - Change as required.
Fuel filter is clogged - Change fuel filter.
Defective safety switch - Replace if required.
Carburetor problems - Carburetor diagnostics required.
Test fuel transfer pump output. Compression problems.

Gas engine starts hard

Faulty spark plug - Check the spark and replace defective spark.
Carburetor not adjusted - Adjust according to instructions.
Clogged fuel pipes - Servicing fuel system.
Choke cable damaged - Replacement required.
Stale or incorrect fuel - Fill in correct fuel.
Electrical wiring worn out - Check and replace.
Starter fault - Check starter, repair or replace.

Engine stalling, surging or running rough

Cooling fins plugged - Clean cooling fins.
Loose electrical connections - Check and repair damaged connections.
Ignition adjust incorrect - Check ignition system and adjust as required.
Throttle cable sticking - Check and change if required.
Air cleaner blocked - Replace air cleaner.

Engine stops or misses

Spark plug wear - Inspect spark plug wire.
Carburetor problems - Test and repair.
Ignition coil not working - Replace defective component.

JD D120 Engine overheats

Excessive engine load - Reduce the load.
Air intake screen blocked - Clean clogged components.
Too little or too much oil - Checking oil level and oil pressure.
Low quality engine oil - Change oil.
Check internal bearing clearance.
Too Fast idle - Adjust carburetor for slower idle speed.

Engine will not idle

Spark plug is loose - Check spark plug gap.
Spark plug wear - Check the spark and replace defective spark.

Engine knocking

Low octane fuel - Use proper fuel.
Engine overload - Reduce loads.
Oil level low - Add engine oil.
Engine speed too low - Adjust carburetor as needed.
Piston rings and cylinder bore are wear - Replace damaged parts.
Check for engine overheating from plugged cooling fins.
Checking and adjusting valve clearance.
Check for carbon build-up in combustion chamber.

John Deere D120 Engine backfires

Checking spark plug.
Check and adjust the choke.
Test carburetor, adjust if necessary.
Check and adjust ignition coil air gap.
Check inlet and outlet valves.
Inspect and set valve clearance.
Inspecting flywheel key.

Insufficient engine power

Engine overheats - Change air filter.
Too much oil in engine - Remove excess oil.
Fuel pump is not working properly - Check fuel pump and replace if required.
Governor is damage - Inspect and repair governor.
Inspect and repair carburetor.
Checking engine compression.

Engine uses too much fuel

Choke is not fully open - Adjust throttle cable.
Incorrect carburetor adjustment - Adjust carburetor.

Black exhaust smoke

Air filter element plugged - Check and clean.
Choke not fully engaged - Inspecting and adjusting throttle.
Check oil fill dipstick O-ring seal or cracked cap.

JD D120 Electrical System Troubleshooting

Starter motor will not turn engine

Main fuse malfunction - Check and change.
Poor terminal connection - Clean terminals.
Battery not charged - Charge the battery.
Ignition lock problems - Replace switch.
Starter is not working - Install new starter.
Wiring disconnected - Change wiring.

Battery doesn't charge

Battery cells defective - Install new battery.
Poor contact between cable and battery pole - Change or clean cable.

Lighting does not function

Light plug disconnected.
Bulbs defective.
Wiring short circuit.

John Deere D120 Machine Troubleshooting

The machine vibrates

Implements driven belt damaged or worn - Inspect and replace damaged belt.
Worn traction drive belt - Install new belt.
Dirt on driven pulley - if required.
Blades bent or out of balance - Change defective blades.

Engine runs but tractor won't move

Parking brake holds the tractor - Unlock park brake.
Bypass valve pulled out - Deactivate the bypass valve.
Mower blade could be loose - Check mower blades and fasten as required.
Improper blade balance - Check mower blade balancing.
Transmission oil is low - Topping up oil.

John Deere D120 Lawnmower Problems

Discharge Chute Clogged

Traveling too fast - Need to reduce speed.
Grass too long - Adjust the mower to a lower cutting height.
Wet grass - Do not mow when grass is wet.
Engine is running at too low speed - The choke is not fully opening.
Loss of airflow - Set higher revs.
Mower cuts too low - Change cutting height.
Belt fitted improperly - Install the belt correctly.

Uncut grass during operation

Clog in discharge area - Clean mower deck.
Blades dull or damaged - Sharpen the blade or install a new one.
Mower deck is low from ground - Deck leveling required.
Grass bag too full - Empty bagger.
Traveling too fast - Need to reduce speed.

Slipping drive belt

Dirt in the pulley - Pulley cleaning required.
Worn belt - Fit new belt.
Belt tension is incorrect - Install the belt correctly.

Excessive mower vibration

Debris in pulleys or in mower deck - Clean sheave and deck from clogging.
Belt or sheaves faulty - Change damaged parts.
Misaligned belt or pulley - Check and centering.
The blades are unbalanced - Blades need balancing.

Blades scalp grass

Cutting too low - Set the proper cutting height.
Mower wheels not adjusted correctly - Check wheel adjustment.
Low tire inflation - Need to inflate tires.
Faster mower blade speeds - Adjust the blade speed.
Bent mower blades - Install new blades.

Uneven Cut

Mower deck not level - Leveling the mower deck.
Tire pressure uneven - Need to inflate tires.
Wrong wheel position - Check wheel adjustment.
Gear too fast - Don't use fast speed.
Blades worn - Sharpen the blade or install a new one.

JOHN DEERE TRACTORS ATTACHMENTS
420	430	455	790	990
X300	X320	X330	X350	X475
X485	X500	X540	X570	X590
X700	X720	X738	X758	1023E
2025R	2210	2520	3025E	3032E
3038E	3038R	3039R	3046R	3203
3320	3520	4052R	4066R	4100
4105	4115	4200	4310	4320
4400	4410	4520	4600	4720

JD TRACTORS TROUBLESHOOTING
2640	3040	3310	3650	4100
5050D	5090R	5410	6105R	7200R
E130	L111	LA110	LT155	X300R