If your lawn mower cranks but won’t start—and you suspect gas isn’t reaching the spark plug—you’re not alone. This problem is one of the most common reasons for a no-start situation. Here’s a step-by-step guide to diagnosing why fuel isn’t reaching the spark plug, and how to fix it quickly so you can get back to mowing.
Quick Picks: Most Common Reasons Gas Isn’t Getting to the Spark Plug
- Empty Tank or Bad Gas: Always start with fresh fuel—old gas can block the entire system.
- Clogged Fuel Filter or Line: Debris can block fuel from reaching the carburetor.
- Dirty or Gummed Carburetor: Old fuel leaves sticky deposits that block internal passages and jets.
- Stuck Float or Needle Valve in Carburetor: If stuck shut, no fuel can flow to the engine.
- Faulty Fuel Pump (on some riding mowers): A worn or broken fuel pump won’t deliver gas to the carburetor.
- Blocked or Missing Carburetor Gasket: A vacuum leak or improper seal prevents fuel delivery.
- Choke Not Working: A closed or malfunctioning choke can block fuel flow at startup.
Buyer’s Guide: Tools and Items You Might Need
- Fresh gasoline
- Carburetor cleaner
- Socket set and screwdrivers
- Fuel line or filter (if replacing)
- Needle nose pliers
- Gloves and safety glasses
Step-by-Step: How to Fix Gas Not Getting to the Spark Plug
1. Check for Fuel in the Tank and Line
- Fill with fresh gasoline if the tank is empty or if the gas is older than 30 days.
- Disconnect the fuel line at the carburetor and place it in a container. Turn on the fuel valve (if equipped) and see if gas flows freely. If not, the line or filter is blocked.
- Replace any clogged fuel filters or lines as needed.
2. Inspect and Clean the Carburetor
- Remove the carburetor bowl (bottom part) and look for sticky residue or dirt.
- Clean the bowl and spray carburetor cleaner through the main jet and passages.
- Check the float and needle valve—ensure they’re moving freely and not stuck.
- Reassemble and try to start the mower again.
3. Test for Fuel at the Spark Plug
- Remove the spark plug after trying to start the mower several times.
- If the plug tip is dry, fuel is still not reaching the combustion chamber.
- If the plug is wet with gas, the problem may be spark-related instead of fuel-related.
4. Check the Choke and Carburetor Gaskets
- Make sure the choke opens and closes properly. A stuck or broken choke won’t let enough fuel through at startup.
- Inspect carburetor gaskets for cracks or improper sealing—replace if needed to prevent air leaks that can block fuel delivery.
5. For Riding Mowers: Check the Fuel Pump
- If your mower has a fuel pump, make sure it’s working. Weak or failed pumps won’t deliver gas to the carburetor.
- Replace the pump if it’s cracked or non-functional.
Comparison Table: Gas Flow Issues & Solutions
| Problem | Solution | Difficulty | Parts Needed |
|---|---|---|---|
| Clogged Fuel Line/Filter | Clean or replace line/filter | Easy | Fuel line/filter |
| Dirty Carburetor | Clean or rebuild carburetor | Easy-Medium | Carb cleaner/kit |
| Stuck Float/Needle | Free up or replace parts | Easy | Needle/float |
| Faulty Fuel Pump | Replace fuel pump | Medium | Fuel pump |
| Bad Gasket/Vacuum Leak | Replace gasket, tighten bolts | Easy | Gasket |
| Stuck Choke | Repair or adjust choke | Easy | — |
Frequently Asked Questions
How do I know if gas is reaching the spark plug?
Remove the spark plug after attempting to start the engine. If the tip is wet with fuel, gas is getting through. If it’s dry, there’s a fuel blockage.
Can I use starting fluid to test for fuel issues?
Yes—spray a small amount into the carburetor intake. If the engine fires briefly, the problem is almost certainly fuel delivery.
What if cleaning doesn’t solve the problem?
If you’ve cleaned the carb, checked lines and filters, and the spark plug stays dry, replace the carburetor or consult a repair shop for deeper engine issues.
Conclusion
If gas isn’t reaching your spark plug, check for blockages in the line or filter, clean the carburetor, test the float, and make sure all gaskets and chokes are working properly. Most fuel delivery problems are quick and affordable fixes—so you’ll be back to mowing with minimal hassle!