* Clogged fuel jets or passages: The carburetor has tiny jets that meter the fuel. These can become clogged with varnish, gum, or debris from old or dirty gasoline. This restricts fuel flow, even if gas is *getting* to the carburetor. Cleaning or rebuilding the carburetor is often necessary.
* Weak or faulty fuel pump: While you say gas is reaching the carburetor, the fuel pump might be delivering insufficient pressure. This means the gas might get there, but not with enough force for proper atomization. Check the fuel pressure.
* Faulty carburetor float level: The float controls the level of gasoline in the carburetor's bowl. If the float is stuck or misadjusted, the fuel level may be too low, leading to a lean fuel mixture (not enough gas).
* Vacuum leaks: Leaks in the intake manifold or vacuum lines can disrupt the proper air/fuel mixture. The engine might run on starting fluid because it's so volatile it can overcome this leak; gasoline can't.
* Ignition problems (less likely): While starting fluid's volatility makes it easier to ignite, very weak ignition (a failing coil, for instance) could be preventing the gas from igniting effectively. However, this is less likely because it would likely show issues even with starting fluid.
Troubleshooting steps:
1. Check fuel pressure: Use a fuel pressure gauge to measure the pressure at the fuel rail (or carburetor inlet if it doesn't have a rail). This confirms if the fuel pump is working correctly.
2. Inspect the fuel filter: A clogged fuel filter will restrict fuel flow. Replace it if necessary.
3. Clean or rebuild the carburetor: This is the most likely solution. You can try cleaning it yourself (lots of online guides available), but a professional rebuild is often the best option for a long-term solution.
4. Check for vacuum leaks: Use a vacuum gauge or spray carburetor cleaner around intake manifold gaskets and vacuum lines while the engine is running. A rising vacuum gauge reading or a change in engine speed indicates a leak.
5. Check the ignition system: While less likely, verify spark strength and timing.
Important Note: Starting fluid should be used sparingly. It's meant as a short-term aid for starting a cold engine, not as a fuel substitute. Excessive use can damage the engine. Addressing the underlying carburetor issue is crucial.
