When your 2021 Lincoln Navigator refuses to start and you detect a strong gasoline odor, fuel is either flooding the engine or leaking externally. Both conditions require investigation before further starting attempts, as fuel vapors create fire hazards.
Engine Flooding
Flooding occurs when excessive fuel enters the cylinders and prevents combustion. This can happen from repeated short starting attempts that don't allow the engine to run long enough to burn off accumulated fuel, or from a stuck-open fuel injector continuously dumping fuel.
Clear Flood Procedure
If you suspect flooding, try the clear flood procedure: press the accelerator pedal fully to the floor and hold it there while cranking for 10-15 seconds. This signals the PCM to cut fuel injection, allowing only air to flow while cranking clears excess fuel from the cylinders. Release the pedal and try a normal start.
Stuck Open Fuel Injector
A fuel injector that fails open continuously dumps fuel into its cylinder. Raw fuel washes down past the piston rings, diluting the engine oil with gasoline. This condition causes hard starting, rough running, and gasoline smell. Check the oil level and smell it - if it's overfull and smells like gas, an injector is likely stuck open.
External Fuel Leaks
Fuel smell without flooding symptoms suggests a fuel leak somewhere in the system. Check under the vehicle for wet spots or drips. The fuel tank, fuel lines, fuel rail, and injector seals are all potential leak points. External leaks are fire hazards that require immediate repair.
EVAP System Issues
A saturated charcoal canister or stuck-open purge valve can cause strong fuel odor and flooding after refueling. If the problem occurs specifically after filling the tank, EVAP system diagnosis is warranted.
Fuel Pressure Regulator Failure
The fuel pressure regulator maintains correct pressure in the fuel rail. A failed regulator can allow excessive fuel pressure, causing rich conditions that may result in flooding and fuel smell. Some regulators fail by leaking fuel into their vacuum connection.