When your lawn mower refuses to start or only sputters for a moment before dying, there’s a good chance it’s not getting gas to the carburetor. This is a common and frustrating issue for all mower owners—push, self-propelled, and riding alike. Fuel delivery problems are usually simple to fix once you know what to look for. This detailed guide will walk you through every step to diagnose and repair a mower that isn’t getting gas to the carb, so you can get back to mowing without delay.
How the Fuel System Works (And Where It Can Fail)
Your mower’s fuel system pulls gas from the tank, sends it through a filter and fuel line, and delivers it to the carburetor, where it mixes with air before entering the engine. If any part of this chain is blocked, cracked, or failing, fuel can’t reach the carb and your mower won’t start.
- Gas tank: Holds the fuel. Needs to be clean, vented, and have fresh gas.
- Fuel filter: Traps dirt before gas reaches the carburetor.
- Fuel line: Carries gas from the tank to the carb. Can become kinked, cracked, or blocked.
- Fuel shutoff valve: Some mowers have a valve that must be open for fuel to flow.
- Carburetor: Mixes air and fuel. If it’s dry inside, fuel isn’t getting to it.
Top Signs Your Mower Isn’t Getting Gas to the Carburetor
- Engine cranks but won’t start, even with fresh fuel
- Engine briefly runs on starting fluid, then dies
- No fuel visible in the clear fuel filter (if equipped)
- Carburetor bowl is dry or empty after repeated starting attempts
- No smell of gasoline at the carburetor intake
- Primer bulb (if equipped) doesn’t squirt fuel or feels flat
1. Is There Fuel in the Tank?
It sounds basic, but always start here! Make sure there’s enough fresh gasoline in the tank. Old, stale, or contaminated gas can also cause fuel system issues.
- Use fresh gasoline (less than 30 days old).
- Check for water or debris at the bottom of the tank.
- If the cap is clogged, a vacuum can form and prevent flow—open the cap and listen for air rushing in.
2. Check the Fuel Filter
The fuel filter is the first place blockages usually occur. If it’s clogged, fuel can’t reach the carburetor.
- Find the filter in the fuel line between the tank and carburetor.
- If it’s dirty, discolored, or filled with sediment, replace it.
- If you can’t blow air through it, it’s blocked.
3. Inspect the Fuel Line
Fuel lines get brittle and can kink, crack, or collapse over time. Blockages or air leaks here are a top culprit.
- Look for visible cracks, bends, or soft spots.
- Remove the fuel line and blow compressed air through it (away from your face!).
- If blocked or soft, replace with new fuel hose of the same diameter.
- If the line collapses when the engine is running, it’s time for a new one.
4. Test the Fuel Flow to the Carburetor
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Turn off the fuel valve (if equipped).
Prevent spills while disconnecting lines.
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Disconnect the fuel line from the carburetor.
Place the end in a clear cup or container.
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Turn on the fuel valve and observe.
Gas should flow freely into the container. If it’s slow, weak, or doesn’t flow at all, there’s a blockage upstream (in the line, filter, or tank).
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If fuel flows strongly, the problem is likely inside the carburetor (see next section).
5. Check the Fuel Shutoff Valve
Many mowers have a small valve between the tank and carburetor. If it’s turned off, or the valve is clogged with debris, fuel won’t flow.
- Make sure the valve is fully open.
- If the handle turns but no fuel flows, remove and clean or replace the valve.
6. Inspect the Primer Bulb (If Equipped)
Some mowers use a primer bulb to move fuel into the carb for cold starts.
- If the bulb doesn’t spring back after pushing, it may be cracked or leaking.
- If no fuel is visible in the bulb after pressing, check the fuel lines to and from the bulb for blockages or leaks.
- Replace the primer bulb if it’s brittle, cracked, or flat.
7. Carburetor: Why Fuel Might Not Reach the Bowl
- The carburetor bowl stores a small amount of gas for the engine to draw on.
- If the bowl is dry, either fuel isn’t reaching it or the float/needle valve inside is stuck closed (common after winter).
- Tap the carburetor gently with the handle of a screwdriver. Sometimes this frees a stuck float.
- If still dry, remove the bowl and check the needle valve for sticking or blockages.
- Clean all passages with carburetor cleaner and compressed air.
- If the float or needle is damaged, replace with a carburetor rebuild kit.
8. Air Leaks and Vacuum Problems
Some mowers use vacuum from the crankcase to help draw fuel. Air leaks in gaskets, seals, or around the carburetor mounting can interrupt fuel flow.
- Inspect gaskets and mounting surfaces for cracks, gaps, or missing bolts.
- Replace gaskets as needed for a proper seal.
9. Fuel Cap Problems: Don’t Overlook This!
If your fuel cap vent is clogged, a vacuum forms in the tank and fuel stops flowing. Try loosening the cap and see if gas starts moving again.
- Clean or replace the fuel cap if you suspect venting issues.
10. Preventive Maintenance: Keep Fuel Flowing Strong
- Use fresh gasoline, and avoid ethanol blends over E10.
- Replace the fuel filter and lines every 1–2 years.
- Add fuel stabilizer if storing your mower for more than 30 days.
- Clean the carburetor annually, especially after winter storage.
- Store your mower with the tank and carburetor empty if possible.
Frequently Asked Questions (FAQ)
How do I know if my mower isn’t getting gas to the carb?
The engine cranks but won’t start, runs briefly on starting fluid, or the carburetor bowl is dry after repeated attempts. You may also see no fuel in the filter or line.
Can a clogged air filter cause no fuel to reach the carb?
No, a clogged air filter can make starting harder, but it won’t stop fuel from reaching the carburetor. Focus on the tank, filter, line, and carburetor itself.
How often should I replace my mower’s fuel lines?
Every 1–2 years, or whenever you see cracking, soft spots, or blockages.
Should I clean or replace my fuel filter?
Most mower fuel filters are cheap to replace. Change them yearly or at the first sign of clogging for best performance.
What if fuel gets to the carb but my mower still won’t start?
The problem may be a clogged carburetor, bad spark plug, faulty ignition, or compression issue. Work through general no-start troubleshooting steps next.
Conclusion: Keep the Gas Flowing for a Healthy Lawn Mower
A mower that’s not getting gas to the carburetor can be incredibly frustrating, but most problems are simple—fuel line blockages, clogged filters, stuck floats, or old gas. By methodically checking each step from the tank to the carb, you’ll quickly find the problem and have your mower running like new. Keep up with preventive maintenance and always use fresh fuel to avoid future headaches. If you suspect deeper issues or need help with carburetor repair, a small engine pro can get you mowing again fast.
With a clear fuel path, your lawn mower will always be ready for the job!