* Pressure: The fuel pump provides the necessary pressure to atomize the fuel properly in the fuel injectors (or carburetor, depending on the engine). Gravity alone won't provide sufficient pressure for reliable operation.
* Volume: The fuel pump supplies a consistent flow of fuel. Gravity feed relies entirely on the height of the fuel source and the length of the fuel line; this is highly variable and insufficient for proper engine operation.
* Safety: Gasoline is highly flammable. A gravity-fed system greatly increases the risk of spills and fires.
* Fuel System Design: The 1989 Ford Ranger's fuel system is designed to work *with* the fuel pump. Bypassing it disrupts the entire system, potentially leading to airlocks, vapor lock, and other issues that will prevent the engine from starting or running.
In short, attempting to bypass the fuel pump is a bad idea. If you're having fuel pump problems, it's crucial to diagnose and repair or replace the pump. Trying to circumvent the pump will likely lead to more problems and potential hazards.
