Is your lawn mower cranking but not starting, or does it sputter and die after just a few seconds? If you have fresh gas in the tank but the mower isn’t running, there’s a good chance it’s not getting fuel to the carburetor and engine. This is one of the most common—and most frustrating—problems for mower owners. The good news? Most fuel delivery issues are easy to diagnose and fix with a little know-how. This guide walks you through every cause, solution, and maintenance tip to get your mower running strong again.
How the Fuel System Works (and Where Problems Happen)
A lawn mower’s fuel system pulls gasoline from the tank, sends it through a filter and fuel line, and delivers it to the carburetor. The carburetor mixes the fuel with air before it goes into the engine. Any blockage, leak, or part failure in this chain will keep your mower from getting fuel and starting.
- Gas tank: Needs fresh, uncontaminated fuel
- Fuel filter: Traps dirt but can clog with use
- Fuel line: Carries gas; can get blocked, cracked, or kinked
- Fuel shutoff valve: Must be open for fuel to flow
- Carburetor: Where fuel and air mix before entering the engine
Common Signs Your Mower Isn’t Getting Fuel
- Engine cranks but doesn’t start, even with fresh gas
- Runs only briefly when you use starting fluid, then dies
- No gasoline smell at the carburetor or air filter intake
- Dry carburetor bowl after repeated starting attempts
- Primer bulb doesn’t fill with fuel or stays flat
- No fuel in the clear fuel filter (if equipped)
1. Is There Fresh Fuel in the Tank?
Always start with the basics! If your gas is old, contaminated, or has water in it, your mower might not run—even if there’s plenty in the tank.
- Drain and replace gas that’s more than 30 days old
- Look for water, debris, or sediment in the tank
- If you hear a “whoosh” of air when removing the cap, the cap vent may be clogged—replace or clean it
2. Check the Fuel Filter
- Find the fuel filter—usually in the line between tank and carburetor
- If it looks dirty, discolored, or is full of debris, replace it
- Try blowing through the filter. If blocked, install a new one
3. Inspect the Fuel Line for Blockages or Leaks
- Look for cracks, kinks, collapsed spots, or mushy sections
- Disconnect the fuel line and try to blow through it (away from your face!)
- If blocked, cracked, or soft, replace it with new fuel hose of the same size
- If fuel leaks at any connection, tighten clamps or replace the line
4. Is the Fuel Shutoff Valve Open?
- Some mowers have a shutoff valve near the tank. Make sure it’s fully open
- If the valve is hard to turn or stuck, replace or clean it
5. Check the Primer Bulb (If Equipped)
- Push the primer bulb. It should draw fuel into the carburetor
- If it won’t spring back or never fills, it may be cracked, leaking, or the line may be blocked
- Replace the primer bulb or any leaking lines as needed
6. Test for Fuel Flow to the Carburetor
- Turn off the fuel valve (if present)
- Disconnect the fuel line from the carburetor
- Place the line in a clear container and turn on the valve
- Gas should flow freely; if not, there’s a blockage upstream
- If gas flows but the carb bowl stays dry, the float or needle may be stuck
7. Carburetor Problems: Float, Needle Valve, and Gummed Up Jets
- If fuel gets to the carb but won’t reach the engine, the float or needle valve could be stuck closed—often from old gas
- Tap the carburetor gently with a screwdriver handle to free the float
- Remove the bowl and clean any varnish, dirt, or debris
- Clean all jets and passages with carburetor cleaner and compressed air
- Install a rebuild kit if the float, needle, or gaskets are worn or damaged
8. Fuel Cap Venting Problems
A clogged fuel cap vent creates a vacuum in the tank, preventing gas from flowing. Try starting the mower with the cap loose. If it runs, the cap is the problem.
- Clean or replace the cap if the vent is clogged
- Always use the correct cap for your mower model
9. Air Leaks and Vacuum Issues
- Check carburetor gaskets and mounting bolts for tightness
- Replace missing or cracked gaskets for a proper seal
- Some mowers use vacuum to help draw fuel—air leaks in the intake can interrupt flow
10. What If Fuel Gets to the Carb, But Engine Still Won’t Start?
- Check the spark plug: Replace if fouled, worn, or damaged
- Inspect the air filter: Replace if dirty or clogged
- If you smell gas at the plug or exhaust, the engine may be flooded (see our flooded engine troubleshooting guide)
- Low compression or internal engine problems can also mimic fuel starvation
Preventive Maintenance Tips for Reliable Fuel Flow
- Use only fresh gasoline (add stabilizer if storing for long periods)
- Replace fuel filter and lines every season or at the first sign of wear
- Drain the fuel tank and run the carb dry before winter storage
- Keep the gas tank and cap clean and debris-free
- Clean or rebuild the carburetor each spring if your mower sits over winter
Frequently Asked Questions (FAQ)
Why does my mower only run with starting fluid?
This means gas isn’t reaching the carburetor or engine—usually a blocked fuel line, clogged filter, or gummed-up carburetor. Work through the steps above to restore fuel flow.
How often should I replace my mower’s fuel lines and filter?
Every 1–2 years or sooner if you see cracking, soft spots, or clogs. Always use ethanol-safe hose and filters.
Can I use carburetor cleaner without taking the carb off?
You can spray cleaner into the carb intake, but a full clean is most effective if you remove the carburetor and clean all jets and passages.
What if my mower still won’t start after fixing the fuel system?
The issue may be with spark, compression, or engine internals. Check the spark plug, air filter, and for signs of engine wear. If needed, consult a small engine repair shop.
Does bad gas cause long-term damage?
Yes—old, stale, or ethanol-blended gas can gum up the carburetor, clog jets, and cause corrosion. Use fresh gas and stabilizer to prevent issues.
Conclusion: Restore Fuel Flow for a Trouble-Free Mowing Season
A mower that’s not getting fuel can be back in action quickly if you check the basics: fresh gas, clear lines, a clean filter, and a properly working carburetor. Most fuel system problems are easy to fix at home with simple tools and replacement parts. Keep up with maintenance, use fresh fuel, and your mower will reward you with reliable starts and smooth mowing—season after season.
Don’t let fuel issues keep you from a neat lawn—fix the flow and get mowing!