Craftsman W 20hp Briggs Stratton Wont Start

Craftsman W 20HP Briggs Stratton Won’t Start: Complete Troubleshooting Guide

When your Craftsman W lawn tractor with a 20HP Briggs & Stratton engine refuses to start, it can quickly turn a routine lawn maintenance day into a frustrating troubleshooting session.

This powerful engine is the heart of many Craftsman riding mowers, and while they’re known for reliability, even the best engines can experience starting problems.

Whether you’re facing a completely dead engine or one that sputters but won’t turn over, this comprehensive guide will walk you through the most common causes and solutions when your Craftsman W 20HP Briggs Stratton won’t start.

In this article, we’ll explore everything from simple fixes you can try immediately to more complex issues that might require professional attention. We’ll also provide step-by-step troubleshooting methods to help you identify and resolve the problem efficiently.

Key Takeaways

Check fuel quality and quantity before anything else
Verify spark plug condition and connection
Inspect air filter for cleanliness and proper function
Test battery and electrical connections
Examine the fuel system components including carburetor
Verify safety switch functionality
Understand when it’s time to seek professional help

The most common reasons a Craftsman W 20HP Briggs & Stratton engine won’t start include fuel issues, ignition problems, clogged air filters, battery failure, carburetor problems, or safety switch malfunctions.

Common Reasons Your Craftsman Mower Won’t Start

Fuel problems are among the most common reasons why your Craftsman mower with a 20HP Briggs & Stratton engine won’t start. Before diving into more complex troubleshooting, always check these fuel-related issues:

Empty Fuel Tank: This might seem obvious, but it’s easy to forget to check the fuel level, especially if the gauge isn’t working properly. Ensure your mower has enough gas to run.

Stale Fuel: Gasoline deteriorates over time, particularly when left unused for extended periods (like over winter). If your fuel has been sitting in the tank for more than 30 days, it may have degraded to the point where it can’t properly ignite.

Water-Contaminated Fuel: Water in your fuel tank can prevent your engine from starting. This typically happens due to condensation in the tank or when refilling in rainy conditions.

Clogged Fuel Filter: A blocked fuel filter restricts gas flow to the engine. If your mower has been running poorly before it stopped starting completely, this could be the issue.

Fuel Line Blockage: Similar to a clogged filter, blocked fuel lines prevent gasoline from reaching the engine. Inspect the lines for visible kinks, cracks, or blockages.

To address these issues:

Drain old fuel and replace with fresh gasoline
Add a fuel stabilizer if you plan to store the mower
Replace the fuel filter annually or when clogged
Check and clean fuel lines
Consider using ethanol-free fuel, as ethanol can attract moisture and cause problems in small engines

If you’ve confirmed the fuel is fresh and flowing properly but your 20 HP Briggs and Stratton engine problems persist, it’s time to look at other potential causes.

2. Ignition System Problems

A functioning ignition system is crucial for starting your 20HP Briggs & Stratton engine. Here are the key components to check:

Faulty Spark Plug: One of the most common reasons for starting failures is a fouled, damaged, or incorrectly gapped spark plug. Signs include visible carbon deposits, corrosion, or damaged electrodes.

Loose Spark Plug Connection: Even if the spark plug itself is in good condition, a loose connection can prevent proper ignition.

Ignition Coil Issues: The ignition coil generates the electrical voltage needed to create a spark. A faulty coil can prevent your mower from starting.

Damaged Flywheel Key: If your mower hit something hard before it stopped working, the flywheel key (a small metal piece that aligns the flywheel with the crankshaft) may have sheared, affecting ignition timing.

How to troubleshoot ignition problems:

Remove and inspect the spark plug for wear or damage
Clean or replace the spark plug if necessary
Check the spark plug gap using a gap tool (typically 0.030 inches for Briggs & Stratton engines, but verify in your manual)
Ensure the spark plug wire is securely connected
Test for spark by connecting the spark plug to its wire, grounding it against the engine, and pulling the starter
If no spark is visible, the ignition coil may need replacement
Check the flywheel key for damage if you suspect impact damage

For more detailed information on ignition system problems, you might want to consult a Briggs and Stratton engine troubleshooting diagram.

3. Air Filter Maintenance

A clean air filter is essential for your engine to breathe properly. When clogged with dirt, grass clippings, or debris, your 20HP Briggs & Stratton engine may struggle to start or run efficiently.

Clogged Air Filter: A dirty air filter restricts airflow to the engine, creating an improper air-fuel mixture that can prevent starting.

Wet Air Filter: If your air filter has become wet from rain or humidity, it may block air from entering the engine.

Missing Air Filter: Running your mower without an air filter allows debris to enter the engine, potentially causing damage and starting problems.

To address air filter issues:

Locate the air filter (typically in a plastic or metal housing on the side of the engine)
Remove the cover and inspect the filter
If the paper filter is dirty, replace it
If it’s a foam filter, clean it with warm water and mild detergent, then let it dry completely
Before reinstalling, add a small amount of engine oil to foam filters (follow manufacturer guidelines)
Make sure the filter is properly seated before securing the cover

Regular air filter maintenance is particularly important if you mow in dusty conditions or have a lot of dry soil in your yard.

4. Battery and Electrical System Failures

For electric-start models, battery and electrical issues are commonly behind starting failures. Here’s what to check:

Dead Battery: If you turn the key and hear nothing or just a clicking sound, your battery may be dead or dying.

Corroded Battery Terminals: Corrosion on battery terminals prevents proper electrical connection.

Loose Battery Connections: Connections that have vibrated loose over time can cause starting issues.

Faulty Solenoid: The solenoid acts as a switch between the battery and starter motor. If defective, your mower won’t start.

Failed Starter Motor: Over time, starter motors can wear out and fail to turn the engine over.

Damaged Wiring: Cracked insulation or chewed wires (often from rodents) can cause electrical shorts or breaks in the circuit.

To troubleshoot electrical issues:

Check battery voltage with a multimeter (should read 12.6 volts minimum)
Clean battery terminals with a wire brush and baking soda solution
Ensure all connections are tight and free of corrosion
Listen for a click when turning the key (indicates solenoid is working)
If the solenoid clicks but the engine doesn’t turn over, the starter motor may be failing
Inspect all visible wiring for damage

Many owners have found that simply addressing battery issues resolves their Craftsman riding mower won’t start with new battery problems.

5. Carburetor Problems

The carburetor mixes air and fuel in the proper ratio for combustion. Problems with this component are common in engines that have sat unused for long periods:

Clogged Carburetor: Old fuel can leave sticky deposits that clog carburetor jets and passages.

Improper Carburetor Adjustment: Incorrect settings can create a fuel mixture that’s too rich or too lean for starting.

Carburetor Gasket Leaks: Worn or damaged gaskets can cause air leaks that disrupt the fuel-air mixture.

Float Issues: A stuck float in the carburetor can prevent fuel from entering the bowl.

Dirty Bowl: Sediment in the carburetor bowl can clog jets and prevent proper fuel flow.

To address carburetor issues:

Try using carburetor cleaner spray first (follow product instructions)
If cleaning doesn’t work, you may need to remove and disassemble the carburetor
Clean all jets, passages, and the bowl with carburetor cleaner
Replace any worn gaskets or O-rings
Check the float for proper movement
Reassemble carefully, making sure all components are correctly positioned

For persistent carburetor issues, see our detailed guide on 20 HP Briggs and Stratton carburetor problems.

6. Safety Switch Malfunctions

Modern Craftsman mowers have several safety switches designed to prevent operation under unsafe conditions. When these switches fail, they can prevent your mower from starting:

Seat Safety Switch: Ensures the operator is seated before allowing the engine to start.

Brake/Clutch Safety Switch: Verifies the brake is engaged or the clutch is depressed before starting.

PTO (Power Take Off) Switch: Makes sure the blade engagement switch is off when starting.

Transmission Neutral Switch: Confirms the transmission is in neutral before allowing starting.

To troubleshoot safety switch issues:

Verify you’re following the correct starting sequence for your model
Check that you’re fully depressing the brake pedal when starting
Ensure the PTO switch is disengaged
Make sure you’re properly seated on the mower
Test for faulty switches by carefully bypassing them temporarily for testing purposes (reconnect after testing for safety)

Remember that these safety features exist for your protection—never permanently bypass or disable safety switches.

7. Engine Compression Issues

Sufficient compression is necessary for your engine to start and run properly. Low compression can be caused by:

Worn Piston Rings: Over time, piston rings can wear out, leading to compression loss.

Damaged Cylinder Head Gasket: A blown head gasket allows compression to escape.

Valve Problems: Improperly seated or damaged valves can affect compression.

Timing Issues: Improper valve timing can result in compression problems.

Testing for compression problems:

Remove the spark plug
Insert a compression gauge into the spark plug hole
Pull the starter cord several times and note the reading
Compare to specifications in your engine manual (typically 90-110 PSI for Briggs & Stratton engines)
Low readings indicate compression problems

Compression issues typically require professional repair unless you’re experienced with small engine rebuilding.

Step-by-Step Troubleshooting Process

When your Craftsman W 20HP Briggs & Stratton won’t start, follow this systematic approach to diagnose and fix the problem:

Initial Checks

Verify fuel level and quality: Ensure you have fresh fuel in the tank.
Check the oil level: Low oil can trigger shutoff switches on some models.
Inspect the air filter: Make sure it’s clean and properly installed.
Examine the spark plug: Look for signs of fouling or damage.
Test the battery: Verify it has sufficient charge (for electric start models).

Basic Troubleshooting Steps

Clean or replace the spark plug:
- Remove the spark plug using a socket wrench
- Inspect for deposits, damage, or improper gap
- Clean with a wire brush or replace if necessary
- Set the correct gap using a feeler gauge
- Reinstall and tighten properly
Verify fuel delivery:
- Remove the air filter to access the carburetor
- Spray a small amount of starting fluid into the carburetor throat
- Replace the air filter
- Attempt to start the engine
- If it starts briefly, you have a fuel delivery problem
Check for spark:
- Remove the spark plug
- Reconnect it to the spark plug wire
- Ground the metal part of the plug against the engine block
- Pull the starter and look for a blue spark
- No spark indicates an ignition system problem
Test safety switches:
- Ensure you’re following the correct starting sequence
- Check that all safety switches are engaged properly
- If you suspect a faulty switch, consult your manual for testing procedures

Advanced Troubleshooting

If basic troubleshooting doesn’t resolve the issue, move on to these more advanced checks:

Carburetor cleaning or rebuilding:
- Remove the carburetor according to your manual
- Disassemble carefully, noting the position of all parts
- Clean all passages and jets with carburetor cleaner
- Replace worn components and gaskets
- Reassemble and reinstall
Fuel system cleaning:
- Drain old fuel from the tank
- Replace the fuel filter
- Inspect and clean fuel lines
- Check for proper fuel pump operation (if equipped)
Electrical system diagnosis:
- Test battery voltage under load
- Check solenoid functionality
- Inspect wiring harness for damage
- Test starter motor operation
Compression testing:
- Remove spark plug
- Insert compression gauge
- Pull starter rope several times
- Note reading and compare to specifications

For more in-depth troubleshooting advice, you might want to review our Briggs and Stratton engines troubleshooting guide.

Seasonal Starting Problems

Different seasons bring unique challenges for starting your Craftsman mower with a 20HP Briggs & Stratton engine:

Spring Starting Issues

After winter storage, mowers commonly suffer from:

Stale fuel issues
Gummed-up carburetors
Dead batteries
Oil viscosity problems

Spring starting tips:

Replace old fuel with fresh gasoline
Clean or rebuild the carburetor if necessary
Charge or replace the battery
Change the oil to ensure proper viscosity
Replace the spark plug
Clean or replace the air filter

Summer Heat Problems

Hot weather can cause:

Vapor lock in fuel lines
Overheating engines
Accelerated battery discharge

Summer starting tips:

Try starting in cooler parts of the day
Keep the engine cooling fins clean
Ensure proper oil levels
Check battery fluid levels (if applicable)
Store the mower in a shaded area when not in use

Fall and Winter Preparation

To prevent spring starting problems:

Add fuel stabilizer to the tank
Run the engine for several minutes to distribute stabilized fuel through the system
Remove the battery and store it in a cool, dry place
Change the oil before storage
Clean the mower thoroughly to prevent corrosion

Planning ahead with proper winterization can prevent many of the Craftsman lawn tractor won’t start no click issues many owners face when spring arrives.

When to Seek Professional Help

While many starting problems can be resolved with DIY troubleshooting, some issues require professional attention:

Consider professional service when:

You’ve exhausted all basic troubleshooting steps
You lack the specialized tools needed for certain repairs
Engine has internal mechanical damage
You’re not comfortable working with fuel systems or electrical components
The engine shows signs of major overheating or seized components
Warranty coverage is still in effect (DIY repairs might void warranty)

A qualified small engine repair technician has the experience and tools to diagnose complex problems quickly and efficiently.

Preventative Maintenance to Avoid Starting Problems

The best way to deal with starting problems is to prevent them in the first place. Follow these maintenance practices to keep your Craftsman W 20HP Briggs & Stratton engine running reliably:

Regular maintenance schedule:

Change oil every 50 operating hours or annually
Replace spark plugs annually
Clean or replace air filters every 25 operating hours
Replace fuel filters yearly
Clean engine cooling fins regularly
Check battery connections monthly during the mowing season

Fuel management:

Use fresh fuel (less than 30 days old)
Consider ethanol-free gasoline for fewer problems
Add fuel stabilizer when storing for more than two weeks
Keep the fuel tank full during storage to minimize condensation

Storage practices:

Clean the mower thoroughly before storage
Store in a dry, protected area
Remove or disconnect the battery
Consider using a battery tender for long-term storage

For more tips on preventing lawn mower problems, check out our guide on Briggs Stratton Intek V-Twin problems.

FAQ: Craftsman W 20HP Briggs & Stratton Starting Issues

Why is my Craftsman lawn mower not starting?

The most common reasons include stale fuel, dirty carburetor, faulty spark plug, clogged air filter, dead battery, or safety switch issues. Start troubleshooting with the simplest possibilities like checking fuel and spark plug before moving to more complex systems.

Why will my Briggs and Stratton engine not start?

Briggs & Stratton engines typically won’t start due to fuel problems, ignition issues, carburetor clogs, or compression loss. A systematic troubleshooting approach checking fuel, spark, air, and compression will usually identify the cause.

What is the first thing to check if a lawn mower won’t start?

Always check fuel first—ensure you have fresh gasoline in the tank. Next, verify the spark plug is in good condition and properly connected. These two simple checks resolve a significant percentage of starting problems.

Why won’t my 4-stroke engine start?

Four-stroke engines like the Briggs & Stratton 20HP commonly fail to start due to fuel issues, ignition problems, air restrictions, or compression loss. Follow a systematic troubleshooting approach addressing each system to identify the problem.

How do I know if my lawn mower carburetor is bad?

Signs of carburetor problems include rough idling, surging, excessive fuel consumption, black smoke from the exhaust, and starting then stalling. If cleaning the carburetor doesn’t help, rebuilding or replacement may be necessary.

Can I use starting fluid on my Briggs & Stratton engine?

Starting fluid can be used sparingly as a diagnostic tool by spraying a small amount into the air intake. If the engine starts briefly then dies, you likely have a fuel delivery problem. However, regular use of starting fluid is not recommended as it can damage engine components.

How long does a lawn mower battery typically last?

A well-maintained lawn mower battery typically lasts 3-5 years. Factors affecting battery life include charging habits, storage conditions, and how frequently the mower is used. Replacing the battery is often a simple and effective fix for electric start issues.

Final Words

When your Craftsman W 20HP Briggs & Stratton won’t start, a methodical approach to troubleshooting will usually reveal the cause. Most starting problems stem from issues with fuel, ignition, air intake, or the electrical system. By following the steps outlined in this guide, you can identify and resolve the majority of starting problems without expensive professional repairs.

Remember that regular maintenance is your best defense against starting problems. Changing oil, replacing filters, and proper fuel management will keep your Craftsman mower starting reliably season after season. For stubborn issues that persist despite your troubleshooting efforts, don’t hesitate to consult a qualified small engine repair technician who can provide specialized diagnosis and repair.

By addressing starting problems promptly and maintaining your mower properly, you’ll extend the life of your Craftsman W 20HP Briggs & Stratton engine and ensure it’s ready to perform when you need it.

Craftsman W 20hp Briggs Stratton Wont Start