Fuel Injection Pump Guide? Function & Types

June 12, 2024 6 min read


The internal combustion process in a car necessitates precise coordination between several engine components to function properly in its intricate sequence of events. Every part, including the injection pump, is vital in attaining the appropriate functionality and performance.

Diesel engines require an injection pump to calculate and pressurise fuel and feed it to each cylinder at the proper time. The pump’s capacity to precisely and promptly provide an air-fuel mixture into the chamber is critical to combustion. Because of this, even a minor flaw in the pump might disrupt the combustion process, resulting in poor performance.

Types of Fuel Injection Pumps

Over the years, several different systems have been developed to control and efficiently perform the fuel injection process. Although many variations exist, these can be broadly categorised into mechanical and electronic techniques. However, the common rail fuel injection pump has recently gained popularity among manufacturers.

Mechanical Fuel Injection Pump

Cars with mechanical injection systems use a mechanical pump to supply fuel directly into the combustion chamber via the injector nozzles. This type of injection pump is primarily found in heavy-duty applications such as trucks, buses, and agricultural equipment.

Mechanical fuel injection systems, in contrast to common rail systems, rely on the movement of the engine pistons to generate precise ignition timing rather than electronically controlled valves. Although this increases power production and fuel economy, the increased component wear may lead to higher maintenance expenses.

Electronic Fuel Injection Pump

The Electronic Fuel Injection (EFI) system consists of two primary compartments: Low-Pressure and High-Pressure. The Low-Pressure part of the EFI consists of the fuel tank, fuel pump, heater, and cooler, whereas the High-Pressure component comprises the fuel injector, the nozzle, the high-pressure pump, and the fuel accumulator.

High demands for lower engine emissions and better, more flexible performance were a major impetus for the introduction of electronically controlled fuel injection systems in the late 1980s and 1990s.

Common Rail Fuel Injection Pump

The ‘rail’, a centralised high-pressure fuel pump, is used by common rail diesel engines to supply pressurised fuel to the injectors. The injectors in the common rail injection system are electronically controlled valves. In response to inputs from an engine management system, the injectors inject precise amounts of fuel into each cylinder.

A common rail injection system allows multiple injections during every combustion cycle, providing finer control of fuel delivery and thus enhancing engine performance. This makes them the preferred choice for today’s diesel engines, as they cover a broad range of operating conditions while achieving stringent environmental regulations and maximum engine performance.

Additionally, these systems include piezo components or solenoid valves, which open and close rapidly to promote improved combustion and effective ignition timing. Compared to mechanical injection systems, common rail systems produce less noise, which makes them perfect for utility (UTE) and passenger automobiles.

Function of Fuel Injection Pump

The fuel injection pump, comprising sensors and control units, plays a major role in the workings of the fuel injection system. These accompanying parts help to regulate the fuel pressure, the timing of the injection, and the duration of the fuel delivery.

Fuel Metering

The fuel metering system in an internal combustion engine makes use of an electronic computer to calculate the intended fuel flow required to maintain an air/fuel ratio. This desired fuel flow is achieved through a basic metering system that takes into account the transfer of fuel from the liquid state, on the wall surface of the intake passages of the engine, to the vapour/gas state in the inducted fuel-air mixture.

Timing and Injection

Injection timing, also known as spill timing, is when the fuel enters the cylinder in the engine during internal combustion. An injection pump is often indirectly driven from the crankshaft by chains, gears, or timing belts. It is also responsible for moving the camshaft. The timing of the pump determines at which point it’ll inject fuel into the cylinder once the piston reaches the BTDC point. Hence, we can infer from this that one can control when combustion will occur by adjusting the fuel injection timing in the engine.

Manufactured diesel engines have a specified injection timing that is recommended per the make and model of your engine. However, one can alter it to receive as much power as possible without breaking legal emission limits.

Fuel Pressure Regulation

The fuel pressure regulator is a crucial component of the electronic fuelled injection system, in its absence the fuel rail will not be able to produce the required pressure necessary to produce a sufficient amount of fuel to support the injectors instead the fuel will drain out and not reach the injectors.

The fuel pressure regulator is composed of two chambers. Out of these two, one of the chambers is subjected to pressure from the fuel rail while the other chamber is subjected to vacuum from the inlet tract.


  • How does a mechanical fuel injection pump differ from an electronic fuel injection pump?

The primary difference between an electric pump and a mechanical fuel pump is that mechanical pumps make use of a moving mechanical pump to transfer the fuel from the tank and into the engine, whereas electrical pumps use electricity and digitally powered pump to move fuel from the tank to the engine.

  • What advantages does a common rail fuel injection pump offer over other types?

Common rail diesel engines offer a greater advantage over other forms of injection pumps. These pumps consume less fuel, are highly reliable, long-lasting, and have a high torque. Diesel engines with common rail pumps emit much less harmful gasesgasses than engines without common rail pumps, so they are also environmentally friendly compared to gasoline engines.

  • What is the primary function of a fuel injection pump in a vehicle’s engine?

The fuel injection pump is one of the most critical and integral components in the fuel injection system. It helps increase the pressure of your engine to produce sufficient fuel at regular intervals in the fuel chamber.

  • How does a fuel injection pump regulate fuel metering to the engine?

In a mechanical system, the fuel charge is precisely metered and pressured by the fuel injection pump before being routed through pipes to the high-pressure injectors in the combustion chamber, where it burns. The resulting combustion gases then move the piston downward. 


To summarise, there are certain components that are crucial in the process of internal combustion, among which are fuel pumps. Whether you drive a diesel truck or gasoline-powered car, the fuel pump plays a vital role in transferring the fuel from the tank to the engine of your vehicle.  This blog has taken you through the three major types of injection pumps. The electronic pump or the modern workhouse is a standard choice for modern vehicles due to its efficiency and reliability. The traditional Mechanical pumps, though not so popular today, are still used in cases of heavy machinery and vintage cars and finally, the new-age technologically advanced high-pressure injection pumps, have recently gained major prominence.

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