Why will a 2000 Pontiac Grand Am not start after running out of gas?

A 2000 Pontiac Grand Am, or any car for that matter, won't start after running out of gas primarily because the fuel pump needs fuel to lubricate itself. Fuel pumps are submerged in the fuel tank and rely on the fuel itself for cooling and lubrication. When the tank is empty, the pump runs dry, leading to overheating and potential damage. This damage can manifest in several ways:

* Burned-out fuel pump: The most likely scenario. The pump overheats and fails.

* Damaged fuel pump motor: The motor within the pump might seize up due to lack of lubrication.

* Damaged fuel pump relay: While less likely, running the pump dry could stress the electrical components controlling it, potentially causing the relay to fail.

Beyond the fuel pump itself, running completely out of gas can sometimes lead to:

* Air in the fuel lines: The pump may have drawn in air, creating airlocks that prevent fuel from reaching the engine. This can sometimes be resolved with a few cranks of the engine after refueling.

* Clogged fuel filter: While less common, any sediment or debris in the tank may become more problematic when the fuel level is very low.

In short, while simply refueling is the first step, if the car doesn't start after that, the most probable cause is a damaged fuel pump requiring replacement. You should have a mechanic diagnose the issue.