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What Is a Fuel Pump and where is it Located?
A fuel pump is a device that moves fuel from the fuel / gas tank up to the engine. They come in a huge variety of shapes and sizes for every possible application that you could ever imagine. There are three main types of fuel pumps – mechanical pumps, in-tank electric pumps, and external electric pumps. Each style has a purpose, and some are more installation-friendly than others.
Mechanical Fuel Pumps
Mechanical fuel pumps are the oldest and most simple design. They have very few moving parts, and are often used on carbureted gas engines and diesel engines. These types of fuel pumps are mechanically driven off of the engine’s camshaft or crankshaft. As the engine speed rises up, so does the fuel pump's fuel volume, which then allows the engine to drink more fuel as needed.
On gas engines, most mechanical fuel pumps are low pressure, which is exactly what carburetors need. They are by far the least expensive fuel pump assembly to buy because of their simplicity and interchangeability. Installation of these fuel pumps is often nothing more than removing two bolts and a couple of hoses. The downfall of mechanical fuel pumps on gas engines though, is that when they fail, they often leak fuel into the crankcase, which thins out the engine oil. This is obviously not ideal for the bearings inside the engine.
For diesel engines, the mechanical pumps need to create extremely high fuel pressure to properly spray the diesel fuel through the injectors. While still a mechanical design, the diesel fuel pumps are more complicated than the style on gas engines. As you can expect, this also means that they come at a far higher price. Because of this, diesel fuel pumps are often professionally rebuilt instead of replaced. Some diesel cars and trucks also have a small electric fuel pump in the fuel tank that feeds the main engine driven mechanical pump. This helps prevent fuel starvation.
Electric Fuel Pumps
Electric fuel pumps are “the norm” for the vast majority of vehicles these days. As you can tell from the name, they are powered by the magic of electricity. They come in two different styles, "internal" and "external".
Internal or In-Tank Electric Fuel Pumps
Internal (also called ”in-tank”) fuel pumps are the most common when it comes to modern vehicles. They are quite literally submerged in fuel inside the gas tank. Being surrounded in fuel keeps the fuel pump cool, but often makes replacing them a bit of a headache. On most vehicles, the only access to the in-tank fuel pump is by removing the fuel tank all together. When a fuel pump assembly is mounted inside the gas tank, the pump is always fitted with a “sock” on the bottom of it. A fuel pump sock is the first barrier for debris floating around inside the fuel tank. It prevents large particles from entering the fuel pump and fuel system. Smaller particles are then caught by the main inline fuel filter further down the line.
External or Inline Electric Fuel Pumps
External (also called “inline”) fuel pumps are located outside of the fuel tank, and usually mounted to the frame of the vehicle. This type of pump can be used in two different ways. Sometimes they are the only fuel pump within the fuel system, but other times they are the “main” high volume fuel pump with a “helper” in-tank fuel pump as a fuel feed for them. This allows high powered engines to maintain the fuel pressure and volume that they require during “spirited” driving conditions. External fuel pumps are obviously easier to replace because the gas tank doesn't need to be touched.
When are Replacement Fuel Pumps Needed?
In the vast majority of cases when a fuel pump assembly needs to be replaced, the engine itself won’t run because it isn’t receiving any fuel. So, that is when a replacement fuel pump would be needed. Now, why do they actually break in the first place? Well, electric fuel pumps can be damaged from a few different things. Age and wear are the most common reasons, but experience says that clogged up fuel socks / filters, and constantly empty fuel tanks will shorten the life of fuel pumps as well.
Replacing a Fuel Pump
Replacing a fuel pump assembly can be really easy or a giant headache depending on the vehicle that you are working on. Most mechanical pumps on gas engines can easily be replaced by any do-it-yourselfer in their driveway. Mechanical fuel pumps for diesel engines are far more complicated and are probably best left to the advanced do-it-yourselfer or a reputable diesel repair shop. Electric fuel pump replacement difficulty can be hit or miss depending on the vehicle. Some are a drama free 15 minute procedure, and some can easily take up an entire day. Grabbing a service manual for your vehicle or doing some good old fashion searching online - including here at 1AAuto.com - can help guide you on your fuel pump replacement journey.
Need a New Fuel Pump Replacement?
If your car or truck is in need of a fuel pump replacement, then you have come to the right place. Whether you need an electric in-tank, inline, external, or mechanical aftermarket fuel pump, 1A Auto makes shopping for them (and understanding them) easy! All of our aftermarket fuel pumps are built to OEM specifications and will install exactly like the original one did. Call our customer service toll free at 888-844-3393 if you have any questions about our products, warranty, compatibility, or to make a purchase.
Written By: Jeremy Nutt
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