How does a Fuel Pump Work?

A fuel pump is a sophisticated piece of equipment whose purpose is to convey the fuel from the fuel tank to the engine, under requisite pressure in order to ensure good combustion and atomization/ dissipation.

Fuel pump enables the engine to run as expected under wide range of fuel consumption rates and driving conditions. They are lubricated and cooled by the fuel that passes through them. When the fuel pump is working effectively, the vehicle runs efficiently and smoothly.

Vehicle Fuel pumps fall into two categories, mechanical and electrical. A mechanical fuel pump is mechanized by another component of the vehicle, the engine. Electric fuel pumps are powered by electricity, which is usually drawn directly from the battery or produced from the vehicle's alternator.

Working of fuel pumps

Mechanical fuel pump (Carburetor equipped engines):

• For generations, mechanical fuel pump was the standard form for delivering fuel to the engine.
• The mechanical pump, bolted to the engine block or the engine's cylinder head, and drive arm, enters the engine and is operated by a flap on the camshaft.
• As the camshaft flips, the arm will be forced to move up and down.
• The movement of the arm at the other end, oscillates the diaphragm thus producing pressure and suction.
• Pressure pushes the fuel to the engine, and suction drew the fuel from the tank.
• The internal check valves restricts the flow of fuel to one direction and prevents bleed back out of the pump.
• A mechanical fuel pump can produce 10-15 pounds of fuel pressure that is enough to feed a carburetor, but an insufficient amount for the fuel injector demands.
• Mechanical fuel pumps are also called as puller pumps. They have a strong suction ability, which is needed to pull fuel from the tank and pump up to the engine. The distance from the carburetor to the pump is relatively short, so puller pumps need not work hard to maintain the pressure in the fuel line.
• With the advent of fuel injection, mechanical fuel pumps gave a way to electric powered fuel pumps.

Electrical fuel pump (Fuel injected engines):

• An electric pump has similar valve-diaphragm arrangement, but instead of the camshaft, an electromagnetic switch (a solenoid) provides the diaphragm pull.
• Due to its electromagnetic nature, the solenoid attracts an iron rod and pulls the diaphragm down, thus drawing fuel into the chamber.
• At the end of its operation, the iron rod pulls apart set of contacts, shattering the field to the electromagnet and finally relaxing the pull on the diaphragm.
• Also, when the return spring of the diaphragm raises the diaphragm, it aids in pulling the rod away from contacts.
• Electric pumps which are also called as pusher pumps are better at forcing/ pushing fuel down the line than at drawing up. They are placed close to the tank and depend on a siphon to get fuel.
• The automotive fuel injection fuel pumps are further divided into "inline" and "in-tank".
• In-tank fuel pump: This type of fuel pumps are found on most vehicles that are driven today.
• The in-tank electric pump can produce 45-65 pounds of fuel pressure, which is optimal for the demands of fuel injected vehicles.
• Placing the pump inside the tank helps to keep the pump cooler, by the receiving fuel or when submersed in fuel that has not been heated up during its passage through the fuel lines.
• In-tank fuel pump performs additional function along with delivering fuel to the engine. It provides a platform for the float arm to attach to and a fuel level indicator.
• The tank float actually floats on the top of the fuel in the tank. Based on its position the fuel level indicator sends signal to the fuel gauge providing information about the volume of fuel to the driver.
• Additionally, the fuel level indicator has a resistor built-in that neglects the sudden movements of the float that may occur during certain driving conditions, like going over bumps or cornering. Thus, this resistor helps to maintain accurate reading and prevents the gauge from being affected by abrupt float movements.
• In-line fuel pump: With advances in technology, inline fuel pump was developed that can be safely placed outside the fuel tank.
• Because it is kept cool by the fuel flowing through it, a constant stream of it must be maintained.
• Stress and balance sensors ensure that, if the pump becomes damaged or clogged or if the engine is rolled or tilted, the pump shuts down, cutting off fuel to the engine and damaging it.
• Inline fuel pumps are used as a substitute for a failed in-tank pump when its removal is going to create an additional repair issue.

Fuel pump buyers can benefit from the information provided in this guide when looking for the exact pump required for their vehicle.

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