Introduction
The Stihl FS38 is a lightweight, gas‑powered string trimmer that many homeowners and landscaping professionals rely on for edging, trimming, and light brush clearing. Knowing How to Start Stihl Fs38 Weed Eater? correctly can save time, reduce frustration, and extend the life of the engine. This guide walks you through every stage of the starting process, from pre‑start checks to troubleshooting common issues, and provides practical tips that make each pull of the starter cord smoother and more reliable.
- Understanding the Stihl FS38 Weed Eater
- Preparing for the First Start
- Step‑by‑Step Starting Procedure
- Easy Starting Tips and Tricks
- Comparison: Cold Start vs. Warm Start
- Common Starting Problems and Solutions
- Maintenance Tips for Reliable Starts
- Safety Considerations When Starting
- Frequently Asked Questions
- Conclusion
Understanding the Stihl FS38 Weed Eater
Features Overview
The FS38 is powered by a 27.2 cc two‑stroke engine that delivers a maximum power output of 0.9 kW (1.2 hp). It weighs only 4.6 kg (10.1 lb) without cutting attachment, making it easy to maneuver for extended periods. The trimmer features a semi‑automatic choke, a primer bulb for fuel delivery, and a throttle trigger with a lock‑out lever to prevent accidental acceleration. The cutting head accepts a variety of line diameters, and the shaft is designed for quick attachment changes.
Engine Basics
A two‑stroke engine completes a power cycle in two piston strokes, meaning it fires once every revolution. This design requires a precise mixture of gasoline and two‑stroke oil (typically 50:1 for Stihl) to lubricate internal components. The carburetor meters this mixture, and the primer bulb draws fuel into the carburetor before the first pull. Understanding these fundamentals helps you diagnose why the engine may refuse to start or run rough.
Preparing for the First Start
Fuel Mixture
Always mix fresh, unleaded gasoline (minimum 89 octane) with a high‑quality two‑stroke oil at the manufacturer‑specified 50:1 ratio. Use a clean, approved fuel container and shake gently to ensure thorough blending. Stale fuel or an incorrect ratio can cause hard starting, excessive smoke, or engine damage. Store mixed fuel no longer than 30 days; discard any older mixture and prepare a fresh batch.
Checking Oil Level
Although the FS38 uses a pre‑mixed fuel, the gearbox (if equipped) may have a separate oil reservoir. Verify the gearbox oil level by removing the fill plug and ensuring oil reaches the bottom of the fill hole. Top up with Stihl‑approved gear oil if low. Neglecting gearbox lubrication can lead to premature wear and noisy operation.
Inspecting the Cutting Head
Before each use, examine the trimmer head for cracked or worn line, debris buildup, and proper line tension. Replace the line if it is frayed or shorter than the recommended length. A clean, correctly loaded head reduces vibration and prevents the engine from bogging down during the first few seconds of operation.
Step‑by‑Step Starting Procedure
Cold Start Procedure
- Place the trimmer on a flat, stable surface with the cutting head clear of obstructions.
- Set the choke lever to the full choke position (usually marked with a snowflake icon).
- Press the primer bulb 5–7 times until you see fuel fill the bulb; this primes the carburetor.
- Engage the throttle trigger lock‑out and hold the throttle trigger at the fast idle position (about 1/4 throttle).
- Grasp the starter handle firmly, pull the cord slowly until you feel resistance, then give a brisk, full‑length pull.
- If the engine coughs but does not run, move the choke to the half‑choke position and pull again.
- Once the engine fires and runs steadily, allow it to warm for 15–30 seconds, then move the choke to the run (off) position.
- Release the throttle trigger lock‑out and let the engine settle at idle before engaging the cutting head.
Warm Start Procedure
- Ensure the trimmer is on a stable surface and the cutting head is clear.
- Set the choke lever to the run (off) position; a warm engine does not need choke.
- Press the primer bulb 2–3 times to refresh fuel in the carburetor.
- Hold the throttle trigger at the fast idle position.
- Pull the starter cord briskly; the engine should start on the first or second pull.
- Allow the engine to idle for a few seconds, then release the throttle lock‑out and proceed to work.
Easy Starting Tips and Tricks
Primer Bulb Usage
The primer bulb is your best friend for reliable starts. Press it until you see fuel fill the bulb completely; this ensures the carburetor bowl is full before the first pull. Over‑priming can flood the engine, so stop once the bulb is firm and fuel is visible.
Choke Position
Use full choke only for a cold engine. If the engine sputters but does not catch, switch to half‑choke rather than repeating full‑choke pulls. Leaving the choke on too long after the engine fires causes a rich mixture, leading to fouled plugs and excessive smoke.
Throttle Trigger Technique
Holding the throttle at fast idle during the pull supplies extra air, helping the engine overcome initial compression resistance. Do not hold the trigger wide open; a quarter‑throttle position is sufficient and prevents the engine from racing once it starts.
Comparison: Cold Start vs. Warm Start
| Aspect | Cold Start | Warm Start |
|---|---|---|
| Choke Setting | Full choke → half choke → run | Run (off) only |
| Primer Bulb Presses | 5–7 presses | 2–3 presses |
| Throttle Position | Fast idle (¼ throttle) | Fast idle (¼ throttle) |
| Typical Pulls Needed | 2–4 pulls | 1–2 pulls |
| Common Issue | Flooding if over‑primed | Hard start if fuel stale |
Common Starting Problems and Solutions
Flooded Engine
If you smell strong gasoline and the engine will not fire, the combustion chamber is likely flooded. Remove the spark plug, pull the starter cord several times to expel excess fuel, dry the plug with a clean cloth, reinstall, and attempt a warm‑start sequence with the choke off.
Spark Plug Issues
A fouled, worn, or incorrectly gapped spark plug is a frequent cause of hard starting. Inspect the plug every 25 hours of operation. Clean deposits with a wire brush, set the gap to 0.5 mm (0.020 in), and replace the plug annually or per the service manual.
Fuel Line Blockage
Cracked or clogged fuel lines restrict flow to the carburetor. Visually inspect the lines for brittleness, kinks, or debris. Replace any damaged sections with genuine Stihl fuel line to restore proper fuel delivery.
Maintenance Tips for Reliable Starts
Regular Cleaning
After each use, wipe down the engine housing, remove grass clippings from the cooling fins, and clean the air filter housing. A clean engine runs cooler and draws air more efficiently, which directly improves starting performance.
Spark Plug Replacement
Replace the spark plug at the start of each season or every 100 hours, whichever comes first. Use the exact Stihl part number (NGK BPMR7A or equivalent) to maintain proper heat range and electrode configuration.
Air Filter Care
The FS38 uses a foam pre‑filter and a paper main filter. Wash the foam filter in warm, soapy water, rinse, and let dry completely before re‑oiling lightly with filter oil. Tap the paper filter gently to dislodge dust; replace it if it appears excessively dirty or damaged.
Safety Considerations When Starting
Always wear eye protection, hearing protection, sturdy gloves, long pants, and closed‑toe boots when operating the trimmer. Keep bystanders at least 15 m (50 ft) away. Never start the engine in an enclosed space; carbon monoxide can accumulate quickly. Ensure the cutting head is not contacting any object before pulling the starter cord, and never attempt to start the trimmer while holding the cutting head or standing on an unstable surface.
Frequently Asked Questions
Why does my Stihl FS38 only start after several pulls when cold?
Cold engines require a richer mixture. If the choke is not fully engaged, the primer bulb is under‑pressed, or the fuel is stale, the engine will need extra pulls. Follow the cold‑start sequence exactly, use fresh 50:1 fuel, and verify the primer bulb fills completely.
Can I use regular automotive gasoline in the FS38?
No. Automotive gasoline often contains ethanol levels above 10 % and lacks the lubricity required for two‑stroke engines. Use fresh, unleaded gasoline with a minimum 89 octane rating and mix with Stihl‑approved two‑stroke oil at 50:1.
How often should I replace the spark plug?
Replace the spark plug at least once per season or every 100 hours of operation. Inspect it every 25 hours; clean or replace if the electrode is eroded, the insulator is cracked, or carbon deposits are heavy.
What should I do if the primer bulb stays soft after pressing?
A soft primer bulb indicates a fuel line leak, a clogged fuel filter, or a cracked bulb. Inspect the fuel lines for cracks, replace the in‑line fuel filter, and ensure the bulb itself is intact. Re‑prime after repairs.
Is it normal for the engine to smoke heavily on the first start of the season?
Light blue smoke is normal for a two‑stroke engine burning the oil‑fuel mixture, especially after long storage. Excessive white or black smoke suggests an overly rich mixture (too much oil or choke left on) or a flooded engine. Adjust the choke, verify the fuel ratio, and clear any flooding before continuing.
Conclusion
Mastering the starting routine for the Stihl FS38 trimmer turns a potentially frustrating task into a quick, reliable process. By preparing the correct fuel mixture, using the primer bulb and choke correctly, and following the step‑by‑step cold‑ and warm‑start procedures outlined above, you will achieve consistent ignition with minimal effort. Regular maintenance—clean air filters, fresh spark plugs, and intact fuel lines—keeps the engine responsive season after season. Remember the safety gear, keep the work area clear, and store the trimmer with a stabilized fuel mix to avoid stale‑fuel problems. With these practices in place, How to Start Stihl Fs38 Weed Eater? becomes a straightforward question answered confidently every time you pick up the tool.