What Is a Fuel System?

Eric Tallberg

As everyone knows, an internal combustion engine needs fuel to operate. Fuel is delivered to the engine by means of the fuel system. The system must be self-contained and efficient so that it will properly energize the engine and will take up as little space as possible necessary to its mechanical functioning. An internal combustion engine's fuel system is, literally, the heart of the engine.

An electric fuel pump, which is used in later model autos.
An electric fuel pump, which is used in later model autos.

Fuel systems today are most commonly associated with the automobile engine. When the automobile's fuel gauge nears empty, the driver must stop and get gas or diesel. The fuel is pumped from the gas/diesel pump down the filler tube into the automobile's fuel tank. This is the storage area for the fuel and where it begins its journey to the engine. A sender that is mounted in or on the fuel tank monitors the amount of fuel in the tank. This information is sent electrically through a relay and wiring to the fuel gauge.

A fuel system delivers fuel to an internal combustion engine.
A fuel system delivers fuel to an internal combustion engine.

When the engine is started, the fuel system is energized. Fuel is drawn from the fuel tank by means of the fuel pump which, on most late-model autos, is mounted in the fuel tank, often alongside the sender. The pump is usually operated electrically from the vehicles battery.

As the fuel system feeds fuel toward the engine, the fuel passes through one, sometimes two fuel filters. These filters may be mounted before or after the fuel pump, or, on some vehicles, both before and after the pump. The fuel filter is essentially a chamber where the fuel is circulated though an organic mesh cloth or paper and any dirt particles are filtered out. A fuel injector’s nozzle openings are minute and are therefore subject to clogging or sticking if the fuel is not completely particle-free.

From the fuel filter, the fuel system conveys the fuel to the fuel injectors for disbursal into the intake valves of the engine cylinders. Fuel injectors in modern automobiles, those built subsequent to 1986, replace carburetors as the preferred method of introducing fuel into the combustion chamber of the engine. In modern systems, fuel injectors are basically computer-controlled valves. Properly operated via computer commands, fuel injectors are capable of opening and closing hundreds of times per second. The fuel injectors will inject, or shoot, fuel directly into the combustion chamber of the engine where it is ignited by the spark plugs and the energy from this detonation drives the crankcase and hence, the automobile.

Proper maintenance of an engine's fuel system is crucial to economically and ecologically efficient operation.

Fuel injection systems eliminate the need for a carburetor.
Fuel injection systems eliminate the need for a carburetor.

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Discussion Comments


@Vincenzo -- Whenever I hear about clogged fuel filters I can't help but wonder where people are buying their gas. I don't think I have ever had a clogged fuel filter and have always figured the gas I was putting in my car was free of crud.

Meanwhile, I will tell you that I have had two fuel pumps fail on me. But those went bad on cars that were at least 10 years old and had over 100,000 miles on them. Considering how much work those things have to do, getting that much mileage out of one is pretty darned miraculous.


Want to know one of the most common failures in a modern fuel system? A clogged fuel filter. It is shocking how often that is overlooked.

I had one go bad years ago and it even baffled the mechanic until he got into the car and figured out what the problem was. I am not even sure if the fuel filter is checked often when I get an oil change.

And isn't it odd that crud in fuel can still cause problems? You'd think that effective filtration methods would have been developed by oil companies by now.

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