5. FUEL SYSTEM MXU 300/250 TROUBLESHOOTING Engine cranks but won't start Engine lacks power · No fuel in tank · Clogged air cleaner · No fuel to carburetor · Faulty carburetor · Cylinder flooded with fuel · Faulty ignition system · No spark at plug · Clogged air cleaner Lean mixture · Intake air leak · Clogged carburetor fuel jets · Improper throttle operation · Float level too low · Intake air leak Engine idles roughly, stalls or runs poorly · Clogged fuel tank cap breather hole · Excessively used choke · Kinked or restricted fuel line · Ignition malfunction · Faulty carburetor Rich mixture · Poor quality fuel · Float level too high · Lean or rich mixture · Clogged air jets · Incorrect idle speed · Clogged air cleaner Misfiring during acceleration · Faulty ignition system · Faulty carburetor Backfiring at deceleration · Float level too low · Incorrectly adjusted carburetor · Faulty exhaust muffler 5-3