Fuel Pump Assembly Replacement Overview


Fuel Pump Overview

The fuel pump is used to supply fuel to the fuel injection system or carburetor of your 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 generating the high pressure 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.

In simpler terms the purpose of a fuel pump is to draw fuel from the gas tank and deliver it to the fuel injector or carburetor. All vehicle engines operate by way of a mechanical pump (Carburetor) or a fuel injected pump (Fuel Injected). 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. If your vehicle is newer 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 inline with the gas tank.

Electric Fuel Pumps

Fuel Pump Modules, which are usually electric, are almost always located within the fuel tank – occasionally they are near the gas tank.  This is done for a couple of reasons, one is to maintain a steady amount of fuel and secondly the fuel pump uses 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 (see O2 Sensor), the contents of the exhaust gases and the actual position of the throttle.

Fuel Pump Failure

There are a couple of reasons why your fuel pump assembly may fail. Electric fuel pump assembly components can experience regular wear and tear. This will cause a gradual loss of pressure and poor engine performance. Some common causes of fuel pump failure are related to rust or dirt that manages to get past the inlet filter sock, which is designed to filter these sediments. When this occurs the fuel pump will stop functioning because the contaminants that have infiltrated the pump may cause it to jam. This will result in having the fuel pump 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 efficiently. Your vehicle’s fuel pump relies on fuel running through it to cool and lubricate it. Starving your fuel pump of fuel can cause your vehicle's fuel pump to overheat and fail. Mechanical fuel pumps usually rupture the diaphragm that is used as the pump, and will leak a small amount of fuel externally (usually from the weep hole) or just not provide the pressure required to get the fuel to the carburetor.

Fuel Pump Replacement

To replace your fuel pump assembly first try to start with an empty gas tank then make sure that the vehicle is in park, for added security the parking brake should be engaged and the front wheels blocked. Next elevate the vehicle with at least two jack stands for safety and disconnect the filler neck from the fuel tank. 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 lower one side of the tank. At this point you should be able to reach the fuel line and wiring connectors. These should be disconnected prior to removing the two other bolts.



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