In many modern cars the fuel pump is usually electric and located inside the fuel tank. The pump creates positive pressure in the fuel lines, pushing the gasoline to the engine. The higher gasoline pressure raises the boiling point. Placing the pump in the tank puts the component least likely to handle gasoline vapor well (the pump itself) farthest from the engine, submersed in cool liquid.

The ignition switch does not carry the power to the fuel pump; instead, it activates a relay which will handle the higher current load. It is common for the fuel pump relay to become oxidized and cease functioning; this is much more common than the actual fuel pump failing. Modern engines utilize solid-state control which allows the fuel pressure to be controlled via pulse-width modulation of the pump voltage. This increases the life of the pump, allows a smaller and lighter device to be used, and reduces electrical load.
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Where is the fuel pump located on a 1991 Chevy Lumina?
In: Fuel Pumps  

Fuel Pump Location
In the fuel tank. There are numerous ways of getting to the pump. A mechanic, or if you cant afford one, like I couldn't, you either drop the tank, nearly impossible, or you take out the back seats, move carpet and insulation, and "cut" a hole in the body to get to it. I have removed lots of tanks to do this for in the past 15 yrs or so, and found this last option a great one, as on the lumina's, without a proper tool, you have to drop the rear axle assembly, pain in the buttux.
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Another benefit to placing the pump inside the tank is that it is less likely to start a fire. Though electrical components (such as a fuel pump) can spark and ignite fuel vapors, liquid fuel will not explode (see flammability limit) and therefore submerging the pump in the tank is one of the safest places to put it. In most cars, the fuel pump delivers a constant flow of gasoline to the engine; fuel not used is returned to the tank. This further reduces the chance of the fuel boiling, since it is never kept close to the hot engine for too long.
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Chevrolet Lumina Fuel Pump Location
Changing a Fuel Pump on a Chevrolet Lumina or a Pontiac Trans Sport