The Stihl BR600 backpack blower is a workhorse for many landscaping professionals and homeowners, renowned for its power and reliability. However, even the most robust machines can encounter issues, and a common culprit behind starting difficulties is a faulty primer bulb. This small, often overlooked component plays a critical role in drawing fuel from the tank into the carburetor, ensuring a smooth and quick start. When your BR600 struggles to fire up, or you notice the primer bulb isn’t doing its job, understanding how to diagnose and repair it becomes essential. This article will guide you through the process, from identifying the problem to replacing parts and getting your Stihl BR600 back to peak performance.
Understanding your Stihl BR600 primer system
Before diving into repairs, it’s helpful to understand what the primer system on your Stihl BR600 does. The primer bulb acts as a small, hand-operated pump, designed to manually pull a small amount of fuel from the fuel tank, through the fuel filter and fuel lines, and directly into the carburetor’s intake. This action essentially “primes” the carburetor, ensuring there’s enough fuel available for the engine to ignite on the first few pulls of the starter cord, especially after the blower has been sitting for a while or run out of fuel. Without a functional primer, you might find yourself pulling the cord repeatedly with no success, or experiencing extremely hard starting.
The system typically consists of:
- The primer bulb: The translucent or opaque bubble you press.
- Inlet fuel line: Connects the primer to the fuel supply (often via the fuel filter).
- Outlet fuel line: Routes the primed fuel into the carburetor.
- Carburetor: The mixing chamber for fuel and air.
Common signs of a primer problem include a primer bulb that:
- Is cracked, torn, or has holes.
- Feels hard, brittle, or has lost its elasticity.
- Doesn’t fill with fuel, or only partially fills, when pressed.
- Doesn’t spring back when released.
Diagnosing the primer bulb problem
When your Stihl BR600 is acting up, a systematic approach to diagnosis is key. Before you start disassembly, always ensure the machine is off and, for safety, disconnect the spark plug wire to prevent accidental starting. Begin with a thorough visual inspection.
Visual inspection of the primer bulb: Carefully examine the primer bulb itself. Look for any visible cracks, tears, or hardening of the rubber or plastic material. A brittle bulb won’t create the necessary vacuum or pressure to move fuel effectively. If it’s collapsed inward and doesn’t fully reinflate, that’s another clear indicator of a fault.
Inspecting fuel lines: Trace the small fuel lines connected to the primer bulb. These lines can become brittle over time, developing tiny cracks that are hard to see. Even a hairline crack can allow air to be sucked in instead of fuel, preventing proper priming. Flex the lines gently to see if they crack or feel excessively stiff. Ensure they are securely attached to the primer and carburetor nipples without any kinks or blockages.
Checking the fuel filter: While not directly part of the primer bulb assembly, a clogged fuel filter inside the fuel tank can severely restrict fuel flow to the primer. If fuel can’t reach the primer bulb, it won’t be able to draw anything. Remove the fuel cap and inspect the filter at the end of the fuel line inside the tank. It should be clean and allow fuel to pass freely. A dirty filter will appear dark and obstructed.
Here’s a quick reference table for common primer symptoms and their potential causes:
| Symptom | Likely Cause(s) | Recommended Action |
|---|---|---|
| Primer bulb cracked/torn | Degraded material, age, exposure to fuel/UV | Replace primer bulb |
| Primer bulb hard/brittle | Degraded material, age, exposure to fuel/UV | Replace primer bulb |
| Primer bulb does not fill with fuel | Clogged fuel filter, cracked fuel line, faulty primer bulb, air leak in system | Check filter, lines; replace bulb if no fuel line/filter issue |
| Primer bulb fills with bubbles | Air leak in fuel line or connection, cracked primer bulb | Inspect fuel lines/connections, check bulb for tiny cracks |
| Primer bulb doesn’t spring back | Degraded material, internal spring failure (less common) | Replace primer bulb |
Step-by-step primer bulb replacement
Once you’ve diagnosed a faulty primer bulb, replacing it is a straightforward repair that most DIY enthusiasts can tackle. Gather your tools: a small flathead screwdriver, needle-nose pliers, a new Stihl BR600 specific primer bulb, and potentially some new fuel lines if they also show signs of wear. Remember to work in a well-ventilated area and always have a fire extinguisher handy when dealing with fuel.
1. Prepare the blower: Ensure the engine is cool. Disconnect the spark plug wire to prevent accidental starting. Ideally, empty the fuel tank or at least ensure the fuel level is low to minimize spills.
2. Access the primer: On the Stihl BR600, the primer bulb is typically located on the carburetor side, often near the air filter assembly. You may need to remove the air filter cover, the air filter itself, or even part of the engine shroud to gain clear access to the primer bulb and its connecting fuel lines. Take photos with your phone before disconnecting anything to help remember the routing of the fuel lines.
3. Disconnect fuel lines: Using needle-nose pliers or a small screwdriver, gently pry off the two fuel lines attached to the primer bulb’s nipples. Be careful not to damage the carburetor’s fuel line nipples if they are shared. Pay close attention to which line goes to which nipple on the primer – typically, one is the inlet (from the tank/filter) and the other is the outlet (to the carburetor). Sometimes the nipples are different sizes or lengths to aid in correct connection. Have a rag ready to catch any small amount of fuel that might drip out.
4. Remove the old primer bulb: The primer bulb is usually held in place by a simple snap-in design or a few small screws. Carefully unclip it or unscrew it from its housing. If it’s brittle, it might break apart during removal.
5. Install the new primer bulb: Position the new primer bulb into its housing, ensuring it snaps securely into place or align the screw holes and fasten it. Make sure it’s seated flush and tight.
6. Reconnect fuel lines: This is a crucial step. Based on your earlier observation or photos, carefully push the correct fuel lines back onto the respective nipples of the new primer bulb. Ensure they are pushed all the way on for a tight seal to prevent air leaks.
7. Reassemble and test: Reinstall any covers or shrouds you removed. Reconnect the spark plug wire. Add fresh fuel if you emptied the tank. Now, press the primer bulb several times. You should see fuel filling the bulb and flowing smoothly through it. Look for any immediate leaks around the connections. Attempt to start your Stihl BR600. It might take a few extra pulls to purge any air from the system, but it should start more easily now.
Addressing fuel line and filter issues
Sometimes, the primer bulb itself is fine, but the system isn’t getting fuel due to issues further upstream. Or, more commonly, the age and exposure that degrade the primer bulb also affect the fuel lines and fuel filter, making it wise to replace them concurrently. Using fresh fuel lines and a new filter can prevent future problems and ensure optimal performance.
Replacing fuel lines: If your diagnosis pointed to cracked or brittle fuel lines, or if they just look old, replacing them is a smart move. Stihl BR600s typically use two main sizes of fuel line: a larger diameter for the main fuel supply from the tank to the carburetor/primer, and a smaller diameter for the return line or the primer lines. Carefully measure the inner and outer diameters of your existing lines to ensure you get the correct replacements. Always use fuel-resistant lines designed for small engines. When replacing, pay close attention to the routing and ensure no lines are kinked or pinched during reassembly. Use a fuel line tool or needle-nose pliers to carefully pull the lines through any grommets or openings in the fuel tank.
Replacing the fuel filter: The fuel filter is located inside the fuel tank, attached to the end of the main fuel supply line. To replace it, drain the fuel tank (or ensure it’s nearly empty). Use a stiff wire, hooked tool, or needle-nose pliers to carefully fish the fuel line out of the tank opening. The filter is usually just pressed onto the end of the line. Remove the old filter, noting its orientation. Press the new fuel filter firmly onto the end of the fuel line. Ensure it’s fully seated for a good seal. Carefully guide the fuel line and filter back into the tank, making sure the filter sits at the bottom where it can draw fuel effectively.
These components are relatively inexpensive but crucial for the overall fuel delivery system. Addressing them while you’re already accessing the primer system can save you time and frustration down the line, ensuring your BR600 runs reliably for many more hours.
Repairing the primer system on your Stihl BR600 backpack blower is a common and highly beneficial maintenance task that can restore your machine’s easy starting and reliable operation. We’ve covered everything from understanding the primer’s function and systematically diagnosing common issues like cracked bulbs, brittle fuel lines, and clogged fuel filters, to providing a detailed, step-by-step guide for primer bulb replacement. We also emphasized the importance of addressing related components like fuel lines and filters, which often degrade alongside the primer bulb. By following these instructions carefully, employing the right tools, and prioritizing safety, you can successfully perform these repairs yourself. This not only saves you money on professional servicing but also deepens your understanding of your equipment, empowering you to keep your Stihl BR600 running efficiently for years to come. A little preventative maintenance and timely repair go a long way in ensuring your powerful blower is always ready when you need it.