* Fuel Pump: This is the most common cause. The pump may be weak, failing, or not getting power. It might be able to provide enough pressure for a short burst to start the engine (with the added fuel), but not enough to sustain operation.
* Fuel Filter: A clogged fuel filter restricts fuel flow. The engine can briefly run with the extra gas but will starve once that's used up.
* Fuel Injectors: While less likely given the symptom, faulty injectors could be failing to deliver fuel consistently. However, if they were completely blocked, it wouldn't even start with the extra gas. A more probable scenario is weak or intermittent injection.
* Relay or Fuse (Fuel Pump Circuit): The fuel pump is electrically controlled. A bad relay or blown fuse would prevent the pump from working. This would be consistent with it running briefly with extra gas and then dying.
* Pick-up in Fuel Tank: If the fuel pick-up tube in the gas tank is clogged or damaged, it can prevent the pump from drawing fuel.
* Pressure Regulator: While less common, a faulty fuel pressure regulator could cause inconsistent pressure, leading to the described issue. The regulator maintains the proper pressure in the fuel rail.
Troubleshooting Steps:
1. Check the Fuel Pump Relay and Fuse: This is the easiest and cheapest thing to check first. Locate the fuel pump relay in the fuse box (often under the hood) and visually inspect it. Check the relevant fuse as well. Try swapping the relay with a known good one (from a different circuit, if possible) to test.
2. Check Fuel Pressure: You'll need a fuel pressure gauge to measure the pressure at the fuel rail. This is the most definitive way to determine if the pump is providing adequate pressure. Compare your reading to the factory specification for your vehicle. Low or inconsistent pressure points to the pump, filter, or regulator.
3. Inspect the Fuel Filter: Locate the fuel filter (usually along the fuel line) and visually inspect it for damage or blockage. If it looks dirty or damaged, replace it.
4. Check the Fuel Pump: This may require accessing the fuel pump (often under the rear seat) to test its operation. You might need to hear if it primes when the ignition is switched on. However, a proper fuel pressure test is a far better diagnosis than simply listening for it.
Important Safety Note: Working with gasoline is dangerous. Always work in a well-ventilated area, away from open flames and sparks. Gasoline fumes are highly flammable and can cause explosions. If you are not comfortable working on your vehicle's fuel system, take it to a qualified mechanic.
