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How
Does it Work /
Fuel Pump
How a Fuel Pump Works
Introduction
A fuel pump is used to supply fuel to the
fuel injection system or carburetor, depending on the year of the
vehicle. Older vehicles use a mechanical pump to deliver low pressure fuel to
the carburetor, while fuel injected vehicles require an electric pump capable of
the high pressures required to make the system work efficiently. A fuel
injection system is more efficient than its predecessor the carburetor and can
better operate in extreme conditions, while becoming more dependable at start
up.
Typical Electric Fuel Pump
Simply put, the purpose of a fuel pump is to draw fuel from the fuel tank then
to deliver it to a fuel injector or carburetor. All vehicle engines operate by
way of a mechanical pump or via a
fuel injected
pump. Chances are if your engine requires a mechanical pump it is quite
old and has fuel pumping at a low pressure from a fuel tank to the carburetor.
Most likely your engine uses a fuel injected pump as do most modern engines and
transfers fuel at high pressure into the fuel injection system from an
electrical pump mounted either inside or outside the fuel tank.
Typical Fuel Injection System
Mechanical PumpsBefore electronic fuel injection, most carbureted
vehicle engines used mechanical fuel pumps to move fuel from the fuel tank into
the fuel sections of the carburetor. However, more recently, as vehicle engines
shifted from carburetors to fuel injection, mechanical fuel pumps are
increasingly being replaced with electric fuel pumps. This is because electronic
fuel injection systems generally run more effectively at higher fuel pressures
than mechanical pumps
Fuel Injected Pumps
Fuel injection pumps, which are usually electric, are located within the fuel
tank or near the gas tank in order to maintain a steady amount of fuel and to
utilize the fuel in the tank to cool the pump. Fuel injection pumps are part of
an electronic system, which means that they are controlled by a
computer system that oversees key factors
including the air to fuel ratio, the contents of the exhaust gases and the
actual position of the throttle.
When Fuel Pumps FailThere are a couple of reasons why your fuel pump
will fail, be it electric or mechanical. Electric fuel pumps can experience wear
and tear on the armature, brushes or bearings. In addition, roller gears and
pump vanes can also wear down. This will cause a gradual loss of pressure and
poor engine performance. Some causes of fuel pump failure can include rust or
dirt because they can get past the inlet filter sock, which is designed to
filter these sediments. When this occurs the fuel pump will break down because
of contaminants that have infiltrated the pump and cause it to jam. This will
result in having the motor overheat and burn out. Sometimes a fuel pump will not
work properly if it is not given the proper amount of fuel needed to run
adequately. Your vehicle’s fuel pump relies on fuel running through it to cool
and lubricate it. Starving your fuel pump for fuel can cause your vehicle's fuel
pump to fail prematurely. Mechanical fuel pumps usually rupture the diaphragm
that is used as the pump, and will leak a small amount of fuel externally (from
the weep hole) or just not have pressure.
How to Replace a Fuel Pump
To replace your fuel pump first start with a nearly empty tank then make sure
that the transmission is in park, the parking brake is activated and the front
wheels are secured. Next elevate the vehicle with at least two jack stands for
safety and disconnect the filler neck from the fuel tank itself. This can be
done by removing the hose clamp that holds the hose to the fuel tank. Then
remove either the rear or front two bolts that fasten the fuel tank to the
vehicle and gently lower one side of the tank. At this point you should be able
to reach the fuel line and wiring connectors, which should be disconnected prior
to removing the two other bolts. Now you can remove the fuel pump from the tank
and insert a replacement pump. When replacing your fuel pump opt for the same
type of pump. Installing a different type of replacement pump can create
difficulties. Your fuel pump is a vital component of the fuel system, so its
electrical draw, flow and pressure characteristics must be in specification with
the remainder of your vehicle’s system. Having a different fuel pump substituted
for another can result in a mismatch, creating durability, noise and, most
importantly, engine performance problems. Always check the system fuel pressure
after a fuel pump replacement. It is also a good idea to replace the fuel filter
and the fuel pump relay when replacing the pump, due to the extra amperage an
old pump can draw through the relay.
Fuel Injection Pressure and Pressure Regulator Test
Fuel Pump Best Practices
When selecting the correct fuel pump for your vehicle’s engine, be sure to
have the engine size, year, make and model of your vehicle. Having this
information handy will allow you to obtain the correct fuel pump specifically
calibrated to your engine's performance specifications. In addition, make sure
the fuel tank is clean. Although this should be self evident you must inspect
the fuel tank carefully to make sure there is no dirt or rust inside and clean
it as needed. Be sure to check the fuel lines for cleanliness as well at this
point. The reason for these examinations is to prevent the most prevalent cause
a fuel system failure, dirt. Take an extra few extra minutes and
replace the fuel filter when replacing the pump.
Basic Maintenance
The main preventive maintenance you can do with a fuel injection system is to
keep your throttle
body
clean and your
fuel filter changed.
How Does it Work
/ Fuel Pump
Additional Resources
Check Manufacturer Specific Fuel
Pump
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