How to Start Fs 38 Stihl Weed Eater? Easy Start Guide

Introduction

The Stihl FS 38 is a lightweight, gas-powered string trimmer that’s a favorite among homeowners and light-duty landscapers for its reliability and ease of handling. Unlike electric or battery-powered trimmers, this 2-stroke model requires a specific starting procedure and proper fuel mixture to run smoothly, which catches many new users off guard. If you’ve been struggling to get your trimmer running, this comprehensive guide will walk you through exactly how to start Fs 38 Stihl Weed Eater, covering cold starts, warm starts, fuel mixing, troubleshooting, and essential maintenance tips to keep your tool in top condition for years to come.

• Understanding Your Stihl FS 38 Weed Eater
• Pre-Start Safety Checks
• Step-by-Step Cold Start Guide for the FS 38
• How to Start a Warm FS 38 Stihl Weed Eater
• Fuel Mixing Guide for Stihl FS 38
• Troubleshooting Common Starting Issues
• Maintenance Tips to Ensure Easy Starts
• Comparison of Start Methods for Different Trimmer Types
• Common Mistakes to Avoid When Starting Your FS 38
• Frequently Asked Questions
• Conclusion

Understanding Your Stihl FS 38 Weed Eater

Before diving into the starting process, it’s helpful to understand the basic design and components of the FS 38, as this will make troubleshooting and operation far simpler. This trimmer is powered by a 27.8 cc 2-stroke gasoline engine, which delivers enough power to cut through thick weeds, tall grass, and light brush around your property. Weighing just 10.6 lbs, it’s lightweight enough for extended use without causing fatigue, and its straight-shaft design gives you precise control for edging and trimming in tight spaces. Unlike 4-stroke engines, 2-stroke models like the FS 38 require a premixed fuel-oil blend to lubricate internal parts, which is a key detail to keep in mind when preparing to start it.

Key Components of the FS 38

Familiarizing yourself with the parts that impact starting will help you follow the procedure more easily. The most important components for starting include:

• Primer bulb: A small rubber bulb located near the fuel tank that pumps fuel into the carburetor to prepare the engine for starting. You’ll see fuel move through the clear tube connected to the bulb when it’s primed correctly.
• Choke lever: A small switch on the side of the carburetor that controls air flow into the engine. For cold starts, the choke restricts air to create a richer fuel mixture; for running and warm starts, it’s set to allow full air flow.
• Throttle trigger and lock: The trigger on the handle controls engine speed, while the lock (if present) lets you hold the throttle at a half-open position for starting.
• Starter cord and recoil: The pull cord on the top of the engine cranks the engine to ignite the fuel mixture. The recoil mechanism retracts the cord after each pull.
• Fuel tank: Holds the premixed 50:1 gas-oil blend required for the 2-stroke engine.
• Air filter: Prevents dust, grass clippings, and debris from entering the engine. A clogged air filter will make starting difficult and reduce engine performance.

Pre-Start Safety Checks

Skipping pre-start safety checks can lead to serious injury, damage to your trimmer, or even property damage. Taking 2 minutes to complete these checks before every start will keep you safe and ensure your trimmer runs reliably. First, inspect the entire trimmer for visible damage: check the cutting head, drive shaft, and handle for cracks, loose bolts, or worn parts. If you notice any damage, repair it before operating the trimmer. Next, verify that you’re using fresh, correctly mixed fuel: old or improperly mixed fuel is the most common cause of starting issues for the FS 38. Clear your work area of all obstacles, including rocks, toys, and garden hoses, and make sure no children or pets are nearby. Always wear appropriate personal protective equipment (PPE), including safety glasses, work gloves, closed-toe shoes, and hearing protection, as trimmers can throw debris at high speeds. Finally, confirm the throttle is in the “off” position and the cutting head is disengaged before attempting to start the engine.

Step-by-Step Cold Start Guide for the FS 38

A cold start is required when the engine has been off for more than an hour, or has cooled completely to ambient temperature. The cold start procedure enriches the fuel mixture to help the engine ignite when it’s not warmed up. Follow these steps exactly for a successful cold start when learning how to start Fs 38 Stihl Weed Eater:

1. Place the trimmer on a flat, stable surface, with the cutting head facing away from you, your feet, and any nearby obstacles. Never try to start the trimmer while holding it, as it could accelerate unexpectedly and cause injury.
2. Press the primer bulb 6 to 8 times slowly. You’ll see fuel move through the clear tube connected to the bulb, which indicates the carburetor is primed. Do not press the bulb more than 8 times, as over-priming will flood the engine with excess fuel and make starting impossible.
3. Move the choke lever to the “cold start” position, which is usually marked with a rabbit icon or labeled “COLD” on the side of the carburetor. This restricts air flow into the engine to create a richer fuel mixture for ignition.
4. Engage the throttle lock (if your model has one) and press the throttle trigger halfway to set the engine to half-throttle. This provides the right amount of fuel for starting without over-revving the engine.
5. Pull the starter cord slowly 2 to 3 times to turn the engine over and draw fuel into the combustion chamber. Then, pull the cord firmly and quickly 3 to 5 times. You should hear the engine sputter or attempt to fire. If it doesn’t start after 5 pulls, wait 30 seconds before pulling again to avoid overheating the starter recoil.
6. As soon as the engine fires and runs for a second, move the choke lever immediately to the “run” position, marked with a turtle icon or labeled “RUN”. Leaving the choke on cold after the engine starts will cause it to stall from excess fuel.
7. Let the engine idle for 30 seconds to warm up fully before pressing the throttle to engage the cutting head. This ensures the engine is running at the correct temperature for optimal performance.

If the engine doesn’t start after following these steps, refer to the troubleshooting section later in this guide for common fixes.

How to Start a Warm FS 38 Stihl Weed Eater

If you’ve turned off your FS 38 for a short break (less than an hour) and the engine is still warm, you can skip most of the cold start steps for a much faster start. Warm starts require less fuel enrichment because the engine is already at operating temperature. Follow these simple steps for a quick warm start:

1. Place the trimmer on a flat, stable surface with the cutting head facing away from you.
2. Leave the choke lever in the “run” position. Do not press the primer bulb, as the warm engine does not need extra fuel to start.
3. Pull the starter cord firmly and quickly 1 to 2 times. The engine should start immediately.
4. Let the engine idle for 10 seconds before pressing the throttle to engage the cutting head.

If the warm engine doesn’t start after 2 pulls, you may need to press the primer bulb once, or adjust the choke to cold for 1 pull before moving it back to run. This is normal if the engine has cooled slightly during your break.

Fuel Mixing Guide for Stihl FS 38

One of the most common reasons the FS 38 fails to start is incorrect fuel mixture. As a 2-stroke engine, it requires a precise blend of gasoline and 2-stroke oil to lubricate internal moving parts, unlike 4-stroke trimmers that use straight gasoline. Using the wrong mix or old fuel will cause starting issues, poor performance, and even permanent engine damage.

Correct Oil-to-Gas Ratio

Stihl officially recommends a 50:1 oil-to-gas ratio for the FS 38, which translates to 2.6 ounces of 2-stroke oil per 1 gallon of unleaded gasoline. Always use fresh gasoline with an octane rating of 89 or higher, and avoid ethanol-blended fuel if possible, as ethanol absorbs water from the air and can degrade fuel lines and clog the carburetor over time. Only use 2-stroke oil that is specifically designed for outdoor power equipment; automotive oil will not provide the right lubrication and can damage the engine. If you don’t want to mix fuel yourself, you can purchase pre-mixed 50:1 Stihl fuel at most hardware and home improvement stores, which is a convenient option for occasional users.

Common Fuel Mixing Mistakes

Even experienced users sometimes make errors when mixing fuel for 2-stroke trimmers. Avoid these common mistakes to ensure your FS 38 starts reliably:

• Using the wrong ratio: Too much oil will cause carbon buildup on the spark plug and exhaust port, making starting difficult. Too little oil will cause insufficient lubrication, leading to engine seizure and permanent damage.
• Using old fuel: Gasoline begins to degrade after 30 days, especially if it contains ethanol. Always mix fresh fuel, and discard any leftover mix that’s older than 30 days.
• Mixing fuel in the trimmer’s tank: Always mix fuel in a separate, clean, approved fuel container first. Mixing directly in the trimmer’s tank can introduce debris and cause inaccurate ratios.
• Using ethanol-blended fuel: Fuel with more than 10% ethanol (E10 or higher) is not recommended for 2-stroke engines, as it can cause corrosion and clogging in the carburetor and fuel lines.

Troubleshooting Common Starting Issues

Even with proper technique, you may occasionally run into starting issues with your FS 38. Most problems are easy to fix with basic troubleshooting. Here are the most common issues and their solutions:

• Engine won’t start after multiple pulls: First, check that you’re using fresh, correctly mixed fuel. Press the primer bulb 2-3 more times, confirm the choke is set to cold for a cold start or run for a warm start, and inspect the spark plug for fouling. If the spark plug is covered in carbon buildup, clean it with a wire brush or replace it with a new Stihl-approved spark plug.
• Engine starts but dies immediately: This is almost always caused by a flooded engine from over-priming or leaving the choke on cold for too long. Move the choke to the run position, pull the starter cord 5-6 times to clear excess fuel from the carburetor, and wait 5-10 minutes for remaining fuel to evaporate before trying to start again.
• Starter cord is stuck or hard to pull: If the cord won’t pull, the engine may be seized from old fuel or lack of lubrication. Check the fuel mix and try adding a small amount of 2-stroke oil to the carburetor to loosen the engine. If the cord is still stuck, the recoil starter may be damaged and need replacement.
• Engine runs rough after starting: A clogged air filter is the most common cause of rough running. Remove the air filter cover, clean the filter with soap and water, or replace it if it’s heavily soiled. Also check that the fuel mix is correct and the spark plug is in good condition.

Maintenance Tips to Ensure Easy Starts

Regular maintenance is the best way to prevent starting issues and extend the life of your FS 38. Follow these simple tips to keep your trimmer running smoothly:

• Replace the spark plug every 25 hours of use, or at least once per season. A worn or fouled spark plug will produce a weak spark, making starting difficult.
• Clean or replace the air filter every 10 hours of use, or more often if you work in dusty or dirty conditions. A clogged air filter restricts air flow, making starting harder and reducing engine power.
• Drain all fuel from the tank and carburetor at the end of each season before storing the trimmer. Old fuel left in the engine will clog the carburetor and make starting impossible in the spring.
• Sharpen the cutting head every 10 hours of use. A dull cutting head puts extra strain on the engine, making it harder to start and reducing cutting efficiency.
• Check the fuel filter every season and replace it if it’s clogged. A blocked fuel filter will prevent fuel from reaching the carburetor, causing starting issues.
• Store the trimmer in a cool, dry place, away from direct sunlight and extreme temperatures. This prevents fuel degradation and damage to plastic and rubber parts.

Comparison of Start Methods for Different Trimmer Types

Starting procedures vary widely depending on the type of trimmer you own. While the FS 38 requires a specific fuel mix and cold start procedure, electric and battery-powered models are much simpler to operate. Below is a comparison of common trimmer types and their start methods to help you understand where the FS 38 fits in:

While electric and cordless trimmers are easier to start and require less maintenance, the Stihl FS 38 offers significantly more power and runtime for larger yards or thick weed growth. Learning how to start Fs 38 Stihl Weed Eater is a small tradeoff for the increased performance and mobility of a gas-powered trimmer, especially for users with demanding yard work.

Common Mistakes to Avoid When Starting Your FS 38

Many starting issues can be avoided by steering clear of these common, easily made mistakes:

• Over-priming the engine: Pressing the primer bulb more than 8 times for a cold start will flood the engine with fuel, making it impossible to start until the excess fuel evaporates. Stick to 6-8 presses for cold starts, and never prime for warm starts.
• Leaving the choke on after the engine starts: The choke is only needed for the initial start. Forgetting to move it to the run position will cause the engine to stall from too much fuel.
• Using old or incorrect fuel: Fuel older than 30 days, or fuel with the wrong oil ratio, is the top cause of starting problems. Always mix fresh fuel with the correct 50:1 ratio before use.
• Pulling the starter cord too hard or too fast: Jerky, forceful pulls can damage the recoil starter mechanism. Pull the cord firmly and smoothly, with a steady motion.
• Skipping pre-start safety checks: Failing to inspect the trimmer or clear the work area can lead to injury from debris or unexpected trimmer movement.
• Storing the trimmer with fuel in the tank: If you won’t use the FS 38 for more than 30 days, drain all fuel from the tank and carburetor to prevent clogs and starting issues when you use it again.

Frequently Asked Questions

How many times do I pull the starter cord to start a cold FS 38?

For a cold start, you should pull the starter cord firmly 3 to 5 times after priming and setting the choke to the cold position. If the engine doesn’t start after 5 pulls, wait 30 seconds before attempting again to avoid overheating the starter. Over-pulling can flood the engine, so stop after 5 attempts and double-check your fuel mix and choke setting before pulling more.

Why won’t my FS 38 start after sitting all winter?

If your trimmer has been stored for several months, the fuel left in the carburetor has likely degraded and clogged the fuel passages. To fix this, drain all old fuel from the tank and carburetor, replace the spark plug, clean the air filter, and fill the tank with fresh premixed 50:1 fuel. If it still won’t start, you may need to clean the carburetor with a carburetor cleaner to remove built-up residue.

Can I use regular gas in my Stihl FS 38?

No, you cannot use straight regular gasoline in the FS 38. It is a 2-stroke engine that requires a premixed blend of gasoline and 2-stroke oil at a 50:1 ratio to lubricate internal moving parts. Using straight gas will cause the engine to seize due to lack of lubrication, leading to permanent and expensive damage. Always mix fresh unleaded gasoline with Stihl-approved 2-stroke oil before filling the tank.

What do I do if my FS 38 is flooded?

A flooded engine occurs when too much fuel enters the combustion chamber, usually from over-priming or leaving the choke on cold for too long after the engine starts. To fix a flooded FS 38, move the choke lever to the “run” position, pull the starter cord 5 to 6 times to clear excess fuel from the carburetor, and wait 5 to 10 minutes for remaining fuel to evaporate before trying to start again. Avoid pressing the primer bulb again until the engine starts successfully.

Does the FS 38 have an easy-start feature?

The standard Stihl FS 38 does not come with a factory-installed easy-start system, but Stihl offers an optional easy-start retrofit kit that reduces the force needed to pull the starter cord by up to 50%. Even without the kit, following the proper cold start procedure outlined in this guide will make starting the FS 38 much easier for most users, especially those who are new to gas-powered trimmers.

Conclusion

Starting the Stihl FS 38 weed eater may seem intimidating at first, especially if you’re used to electric or battery-powered trimmers that require no fuel mixing or special procedures. But by following the steps outlined in this guide, you’ll master how to start Fs 38 Stihl Weed Eater quickly and safely, no matter if it’s a cold start or a warm start. The key takeaways are to always use fresh, correctly mixed 50:1 fuel, follow the proper priming and choke procedure for cold starts, skip priming and keep the choke on run for warm starts, and perform regular maintenance to prevent starting issues. Avoid common mistakes like over-priming and using old fuel, and you’ll get years of reliable performance from your FS 38. With a little practice, starting your trimmer will become second nature, and you’ll be able to tackle yard work quickly and efficiently without unnecessary frustration.