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John Deere 420 - Problems and Solutions

John Deere 420 Engine Troubleshooting

Tractor engine starting problems

No fuel in fuel tank - Fill fuel up.
Wrong fuel grade - Use correct gasoline grade.
Stale fuel - Drain gasoline and fill fresh up.
Dirt and debris in fuel system - Remove debris and dirt.
Plug connection defective - Inspect and replace if required.
Spark plug not working - Installing new spark plug.
Fuel filter is plugged - Fuel filter needs to be replaced.
Safety contact for brake pedal defective - Install new part.
Carburetor is clogged - Clean the carburetor.
Inspect and adjust choke. Check and adjust valve clearance.

Engine is difficult to start

Faulty spark plug - Test spark and replace as required.
Carburetor incorrectly set - Set carb correctly.
Fuel lines are clogged - Clean fuel system components.
Throttle cable worn - Install new throttle cable.
Old or incorrect fuel - Fill in proper fuel.
Loose or corroded electrical connections - Inspect and change wires if required.
Starter problems - Check starter, repair or replace.

Rough running engine

Plugged cooling fins - Remove dirt from cooling fins.
Electrical contacts are damaged - Check and restore defective connections.
Ignition adjustment lost - Check ignition system and adjust as required.
Throttle cable sticking - Check and repair.
Air cleaner dirty - Replace air cleaner.

Engine stops or misses

Faulty spark plug - Change spark plug.
Carburetor problems - Test and repair.
Ignition coil air gap incorrect - Check and adjust ignition coil air gap.

Engine overheats

Excessive engine load - Reduce loads.
Air inlet or cooling fins blocked - Clean clogged components.
Engine oil low or too high - Add or drain oil.
Poor quality oil - Change engine oil.
Check internal bearing clearance.
Idle speed problems - Adjust fast idle.

Engine doesn't idle speed

Spark plug not gapped correctly - Check tightness of spark plug.
Faulty spark plug - Check the spark and replace defective spark.

JD 420 Engine knocking

Stale or low octane fuel - Change fuel.
Engine overloaded - Reduce loads.
Lack of engine oil - Add engine oil.
Low engine speed - Adjust carburetor.
piston rings or cylinder bore damaged - Replace defective components.
Inspect for engine overheats from clogged cooling fins.
Check and adjust valve clearance.
Check for loose or worn connecting rods.

Engine back-fire

Checking spark plug.
Adjust or replace throttle.
Check and adjust carburetor.
Inspect and adjust ignition coil air gap.
Check inlet and outlet valves.
Check valve clearance, adjust if required.
Checking flywheel key.

Engine loses power

Engine overheats - Clogged air filter element.
Excess engine oil - Drain excess oil.
Fuel pump problems - Repair or replace fuel pump.
Faulty governor - Inspect and repair governor.
Check carburetor float adjustment.
Checking engine compression.

Engine using too much gasoline

Choke is not fully open - Adjust choke cable.
Carburetor problems - Check and adjust carburetor.

Exhaust with black smoke

Air cleaner element clogged - Clean or change filter.
Throttle is partially engaged - Check and repair throttle.
Check and adjust carburetor float level.

John Deere 420 Electrical System Troubleshooting

Starter does not function

Main fuse defective - Install new fuse.
Battery contacts are corroded - Clean terminals.
Battery is discharged - Battery charging required.
Ignition lock is damaged - Replace the lock.
Damaged starter - Repair or replace.
Wires disconnected - Replace electric wires.

Battery doesn't charge

Battery cells fails - Fit new battery.
Poor contact between cable and battery pole - Clean or change cable.

No Lights work

Light plug not connected.
Replace light bulbs.
Wiring short circuit.

JD 420 Machine Problems

The machine vibrates

Attachment driven belt worn or damaged - Belt replacement required.
Traction drive belt damage - Install new belt.
Dirt on drive sheaves - Change if necessary.
Mower blades problem - Balance the blades or replace.

Tractor will not move with engine running

Parking brake is applied - Release the park brake.
Bypass valve lever is engaged - Deactivate the bypass valve.
Mower blades are loose - Check mower blades and fasten as required.
Incorrect blade balance - Balance the blades correctly.
Too little transmission oil - Topping up oil.

John Deere 420 Mower Deck Troubleshooting

Clogged discharge chute

Travel speed too fast - Operate the mower at low speed.
Grass Too Tall - Adjust the mower to a lower cutting height.
Wet grass - Don't mow while wet grass.
Low engine speeds - Increase engine speed.
Restricted air flow - Check engine rpm.
Mower deck set to low cutting - Adjust to higher cutting.
Belt is loose - install belt as required.

Streaking of uncut grass

Clog in discharge area - Inspect and clean cutting deck.
Blade wornout - Sharpen the blade or install a new one.
Mower deck is low from ground - Deck leveling required.
Grass bagger overfilled - Clean grass bag.
Travel speed too fast - Operate the mower at low speed.

Slipping drive belt

Dirt in the sheaves - Need to clean the pulley.
Worn belt - Fit new belt.
Low belt tension - Belt tension needs to be adjusted.

Mower vibrates

Mower clogged or in pulleys - Remove debris from the pulley or deck.
Damaged mower belt or pulleys - Install new components.
Belt or pulleys out of centering - Check and align.
Incorrect blade balancing - Blade balance required.

Blade strips grass

Cutting too low - Raise cutting height.
Mower wheels not adjusted correctly - Check wheel adjustment.
Tires inflated insufficient - Inflate tires as required.
High blade speed during mowing - Correct blades speed.
Bent blades during operation - Install new blades.

Uneven Cut

Mower deck not leveled properly - Checking and adjust deck height.
Tires inflated insufficient - Inflate tires as required.
Incorrect rollers height - Adjust rear or front wheel height.
Operating at a faster ground speed - Need to reduce speed.
Blades blunt - Installing new 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