What must be confirmed before testing the fuel system?

Before testing the fuel system, it is essential to confirm that there is fuel in the tank. This step is crucial because if the tank is empty, the engine will not start or run, leading to unnecessary troubleshooting and diagnostics. Ensuring that fuel is present allows for a more efficient test of the fuel system's operation, including fuel delivery to the engine components and proper combustion.

While factors like the engine's temperature, cleanliness of the air filter, and oil presence in the fuel are important for overall engine function and maintenance, they do not directly impact the initial testing of the fuel system like confirming the presence of fuel does. Without fuel, any further checks or tests would be moot, highlighting the necessity of this initial confirmation step.