What is the likely cause of fuel leaking from the carburetor discharge nozzle when the engine is not running?

• A. Leaking float needle valve and seat
• B. Worn throttle plate
• C. Faulty pressure relief valve
• D. Damaged accelerator pump diaphragm

Answer: (A)

Fuel leaks from the discharge nozzle when the engine is not running usually come from the float bowl being allowed to overflow. The float mechanism meters fuel by lifting a needle valve off its seat as the bowl fills. If the needle valve or its seat is worn, damaged, or fouled, it won’t seal properly, so fuel continues to flow into the bowl and out through the discharge nozzle even with no engine vacuum to draw it in. Gravity then drips excess fuel from the nozzle.

Other issues—like a worn throttle plate, which affects air flow and mixture; an accelerator pump diaphragm, which would spray fuel during throttle movement; or a pressure relief valve, which isn’t typically part of a carburetor’s normal float system—don’t explain fuel dripping from the nozzle when the engine is idle. The worn or leaking float needle valve and seat is the most likely cause.