1. No Fuel Supply:
* Empty fuel tank: The most obvious cause.
* Fuel pump failure: The pump doesn't deliver fuel to the engine. This can be due to a blown fuse, faulty relay, a malfunctioning pump itself, or lack of power to the pump.
* Clogged fuel filter: A blocked filter prevents fuel from reaching the engine.
* Blocked fuel lines: Debris or corrosion can restrict fuel flow.
* Fuel tank vent restriction: If the tank can't vent properly, it creates a vacuum preventing fuel from being drawn out.
* Fuel pump relay failure: A faulty relay prevents power from reaching the fuel pump.
2. Low Fuel Pressure:
* Weak fuel pump: The pump delivers fuel, but not at sufficient pressure.
* Leaking fuel injectors: Fuel leaks out instead of being sprayed into the cylinders.
* Leaking fuel lines or fittings: Pressure is lost due to leaks.
* Fuel pressure regulator malfunction: This component regulates the fuel pressure, and a failure can lead to insufficient pressure or excessive pressure.
3. Fuel Delivery Problems:
* Faulty fuel injectors: Injectors may be clogged, stuck open, or stuck closed, preventing proper fuel delivery.
* Incorrect fuel type: Using the wrong type of fuel (e.g., gasoline in a diesel engine) will prevent starting.
* Air in the fuel lines: Air bubbles disrupt fuel flow.
4. Ignition Issues (Related to Fuel):
* Lack of spark (indirectly fuel-related): While spark is an ignition system problem, a lack of fuel can prevent the engine from firing even if the spark is present. A lean fuel mixture due to any of the above causes means there's insufficient fuel to burn effectively despite having spark.
It's important to note that these problems often present with other symptoms beyond just the inability to start the engine. For example, a weak fuel pump might cause hesitation or poor performance before it completely fails. Diagnosing the exact cause requires systematic testing.
