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John Deere L120 - Problems and Solutions

John Deere L120 Engine Troubleshooting

Engine not starting

No fuel in fuel tank - Add fuel.
Incorrect fuel grade - Change fuel.
Old gas - Drain fuel and replace with fresh fuel.
Dirty fuel lines - Inspect and clean.
Spark plug defective - Check wires connection.
Spark plug not working - Test ignition spark.
Fuel filter is plugged - Fit new filter.
Brake pedal not depressed - Press the brake pedal.
Carburetor is not adjusted - Check carburetor float adjustment.
Inspect and adjust throttle cable. Compression problems.

Engine starts hard

Spark plug wear - Check the spark and change defective spark.
Carburetor not adjusted - Adjust according to instructions.
Fuel lines are clogged - Remove clogging from fuel pipes.
Throttle cable worn - Install new throttle cable.
Old or incorrect fuel - Drain and add proper fuel.
Electrical connection problems - Inspect and change wires if required.
Starter is not working - Check starter, repair or replace.

Engine runs unevenly

Cooling fins blocked - Remove dirt from cooling fins.
Electrical connections damaged - Check and repair damaged connections.
Ignition adjust incorrect - Check spark plug and ignition.
Choke cable sticking - Check and repair.
Air filter dirty - Clean or change air filter.

Engine runs but misses

Spark plug worn out - Check spark plug wire for wet or deteriorated condition.
Carburetor defective or not adjusted - Repair or adjust.
Ignition coil air gap incorrect - Check and adjust ignition coil air gap.

Engine overheats

Excessive engine load - Reduce the load.
Cooling fins or air inlet plugged - Clean dirty components.
Engine oil high or too low - Check oil level. Test engine oil pressure.
Poor quality oil - Change oil.
Check internal bearing clearance.
Idle speed problems - Adjust carburetor for slower idle speed.

Engine does not idle

Spark plug not gapped correctly - Adjust spark plug gap.
Spark plug malfunction - Check the spark and change defective spark.

JD L120 Engine knocking

Low octane gasoline - Use proper gasoline.
Engine overloaded - Reduce loads.
Low oil level - add oil as required.
Low engine speed - Adjust the required speed.
piston rings or cylinder bore damaged - Replace damaged parts.
Inspect for engine overheats from clogged cooling fins.
Inspect and adjusting crankshaft end play.
Check for worn crankshaft or camshaft bearings.

Engine back-fire

Check spark plug for fouled.
Adjust or change the choke.
Test carburetor, adjust if necessary.
Check and adjust ignition coil air gap.
Check for sticking valves.
Check and adjust valve clearance.
Inspecting flywheel key.

Insufficient engine power

Engine overheats - Replace air cleaner.
Too much oil in engine - Drain excess oil.
Defective fuel pump - Testing fuel pump output.
Governor problems - Checking and adjusting governor.
Inspect carburetor for plugged passages.
Test engine compression.

Engine gets too much gas

Throttle did not open fully - Replace choke cable.
Carburetor is not adjusted - Checking and adjusting carburetor.

Exhaust with black smoke

Air filter element plugged - Inspect and clean.
Throttle is partially engaged - Inspect and adjust throttle.
Checking and adjusting carburetor float level.

John Deere L120 Electrical System Troubleshooting

Starter does not run

Blown fuse - Installing new fuse.
Battery terminals are corroded - Clean connections.
Battery discharged - Charge the battery.
Ignition lock is damaged - Installing new lock.
Starter fault - Repair or replace.
Wiring disconnected - Change wiring.

Battery will not charge

Dead cell in the battery - Replace the battery.
Bad contact between battery pole and cable - Clean or change cable.

Lights do not work

Connection/disconnection level in wrong position.
lamp does not work.
Short-circuit in cable.

JD L120 Machine Problems

Excessive tractor vibration

Implements driven belt damaged or worn - Check and replace worn belt.
Worn traction drive belt - Installing new driven belt.
Dirt on driven pulley - Replace if necessary.
Mower blades problem - Change as needed.

Tractor will not move with engine running

The parking brake is locked - Release the parking brake.
Bypass valve lever is engaged - Deactivate the bypass valve.
Mower blade could be loose - Check mower blades and fasten as required.
Blades are unbalanced - Check mower blade balancing.
Too little transmission oil - Add transmission oil.

John Deere L120 Lawn Mower Troubleshooting

Discharge Chute Plugged

Ground speed too fast - Need to reduce speed.
Grass too long - Adjust cutting height.
Grass too wet - Wait until later to cut.
Low engine speeds - Open throttle wide.
Restricted air flow - Check engine rpm.
Lack of cutting height - Change cutting height.
Belt installed improperly - install belt as required.

Lawn mower leaving uncut grass

Debris in mower deck - Check cutting deck and clean if necessary.
Damaged blade - Checking for blade fault and change if required.
Mower deck is low from ground - Checking and adjust deck height.
Grass bag too full - Clean grass bag.
Ground speed too fast - Choose recommended speed.

Slipping drive belt

Dirt in the pulley - Recommend cleaning the sheaves.
Belt is damaged - Inspect and replace worn belt.
Poor belt tension - Install the belt correctly.

Too much mower vibration

Debris on mower deck or in sheaves - Remove clogging from sheaves or mower deck.
Pulley or belt faulty - Replace defective parts.
Belt or sheaves no adjustment - Check and adjust.
Incorrect blade balancing - Balance blades properly.

Blades scalp grass

Wrong cutting height - Set the correct cutting height.
Mower wheel height incorrect - Adjust front or back wheel height.
Tires inflated insufficient - Need to inflate tires.
Faster mower blade speeds - Adjust the blade speed.
Bent blades during operation - Remove bent blade and install new one.

Uneven Cut

Deck level is too low - Level mower deck.
Tires inflated insufficient - Tire pressure required.
Incorrect wheel height - Check the wheel heights.
Operating at a faster ground speed - Need to reduce speed.
Mower blades blunt - Sharpen or replace blade.

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