A Complete Guide to Help You Understand Injection Pumps

6 Mins read

Also known as a diesel fuel injection pump, an injection pump is a mechanical device that facilitates diesel transportation into a vehicle’s internal combustion chamber. The injection pump is one of the most critical parts of the entire diesel engine, allowing the latter to maintain its rhythm and operation for as long as possible. 

Thanks to its functionality, we can draw several importances for the injection pump. These include the following: 

  • It provides the engine with fuel, allowing it to continue running. This process involves compressing fuel to a high pressure, where it is eventually lifted to the plunger and fed to the injectors. 
  • The injection pump is also in charge of adjusting the fuel quantity. When the fuel fed into the engine is adjusted with its speed, and there is no change to the timing, the fuel dissipation will be altered. Acceleration generally changes when the engine’s output is proportional to the quantity of injected fuel.  
  • The injection pump can also help to adjust the injection timing. It manages the timing from the point where fuel is injected, united, and combusted all to the point where you reach maximum combustion. 

Most high-performance vehicles tend to have one injector for a cylinder, while the pump injects the diesel right into the injector chamber. Hence, the “fuel injector” moniker. Here, a process occurs where the fuel moves from the injection pump to the combustion chamber. 

During this process, an electronically-controlled valve sends a signal that transports pressurized fuel into the fuel injector. The fuel then enters the plunger, which prepares it for its final exit. When the fuel leaves the fuel injector, a small spray tip is present to distribute it as a fine mist. 

These days, injection pumps have had to improve their pressure ratings. A decade ago, most injection pumps were required to process fuel at about 10,000 to 15,000 PSI. Now, capacities are almost double, with some injection pumps currently working at 40,000 PSI. 

High-end engine performance will depend on how much fuel an engine can process in more ways than one.  

The Different Types of Injection Pumps 

Inline Pumps 

Also called jerk pumps, inline pumps are usually built from the parts of separate pumps. Plunger units are connected inline, with one unit per cylinder. Most inline pumps are activated through a mechanically connected cam that is attached to the engine. 

Among others, the main components of an inline pump are the following: 

  • A camshaft, with the number of cams varying based on the number of plungers
  • A plunger, which increases the fuel pressure 
  • A fuel barrel, which is a tiny space that holds fuel before it is sent into the injector. 

When the crankshaft rotates, the camshaft pump does the same thing. This rotation causes the camshaft to press against the plunger. These cause an increase in fuel pressure, leading to the fuel being sprayed from the injector.

Distributor Injection Pumps 

A distributor injection pump comes with a single fuel-metering plunger. In these pumps, a motor spins and makes a hydraulic connection with different ports on the distributor’s head. Distributor injection pumps are especially notable because they are smaller. Their relatively smaller size comes from the fact that they have single plungers, and the fuel shots are the same. These pumps also have fewer moving parts compared to the inline pumps. 

Common Rail Injection Pumps 

With these injection pumps, most of the power is used to determine the pressurized fuel’s delivery timing and quantity. Most of these injection systems work for petrol and diesel engines. 

Electric Pumps 

Electric pumps are the staple in most modern vehicles. The pumps are located in the fuel tank, and they create positive pressure in the fuel lines. From there, the pump pushes the fuel into the engine. Any vehicle with an electric injection pump will have an electronic control unit and will be programmed with a safety mechanism to shut it off when the fuel cycle is complete.

Injection pumps come in different types, many of which can be bought at authorized dealers. You can check out if you need pumps from different manufacturers, based on your specifications. 

Common Causes of Injection Pump Failure  

Generally, there are two significant causes of injector pump failure. These are poor-quality fuel and defective materials in the pump’s mechanical housing. You will find that most of the issues can easily be traced back to one of these. 

With that in mind, here are some of the most prominent injector pump problems: 

Dirty Fuel

Using dirty or low-quality fuel is one of the most popular reasons why injector pumps can stop working. Over time, residue like grease or debris can build up in the fuel system and clog it up. 

Generally, you will need to examine the spray tip the most when it comes to this problem. This is the area where fuel moves into the combustion chamber, and it is most susceptible to clogging up. If you notice that your vehicle’s engine starts to sputter or delay when you accelerate, you could be dealing with a clogged-up injector pump. 

Driving on Low Fuel 

You should never drive a vehicle with an almost empty diesel engine. Most experts will recommend that you try to, at least, keep it filled up top 75 percent at all times. Remember that fuel provides lubrication to injection pumps. When there’s enough diesel, the fuel pump bearings receive adequate lubrication.

If the tank is empty, air will eventually make its way into the tank, accelerating the wearing process on your bearings. Ultimately, your injection pump will be unable to get the required fuel at the proper pressure levels.  

Deposits in the Injection Pump 

The excessive buildup of physical deposits can also cause injection pumps to fail. 

Generally, there are two types of deposits – internal and external. External deposits occur due to fuel that isn’t wholly burned. The fuel builds up around your injector holes, leading to the accumulation of these deposits. While these external deposits don’t usually lead to pump failure, they can accumulate enough to obstruct fuel spray. Over time, they reduce the efficiency of fuel combustion. You will begin to notice this when your vehicle consumes a lot of fuel and still produces less power.

Now, on to the internal deposits. Unlike the external deposits, these don’t build up on the injector’s outer tips. Instead, they form right on the injector’s inner parts, such as the injector needles and pilot valves. You can usually find internal deposits in newer engines that have highly engineered fuel injection systems. As they build up, they increase fuel consumption and reduce power output. 

Excessive Wear

Excessive wear is another major cause of injection pump failure. This has been a particular problem in the United States ever since authorities mandated using Ultra-Low Sulfur Diesel (ULSD). Essentially., the fuel found in the United States up until 2006 contained high amounts of sulfur – a byproduct of crude oil processing that helped lubricate fuel systems. 

When refiners took out the sulfur component, its lubricating elements disappeared as well. Now, most refiners throw in additives to help improve lubrication. However, it isn’t enough. The more fuel is unable to lubricate, the greater the wear on your machines.  


Besides fuel lubrication, another cause of excessive wear is abrasion. Al fuels – no matter the quality – have small quantities of impurities in them. Some of these impurities could include the smallest microscopic particles that can easily sift through the tightest filters. If these particles are in your diesel, they will be able to cause abrasion in the injectors with time. 

In extreme cases, abrasion can also change the fuel spray pattern, reducing the engine’s performance and leading to high maintenance expenses. With engine downtime also increasing, you will be getting far less value for the money you paid.

Abrasion damage can be reduced by improved housekeeping practices on the fuel supplier’s part and proper filtration practices.  

Bad Injector Timing 

It is critical to provide the ideal amount of fuel – and in good time! The combination of these factors improves fuel combustion regulation and optimizes the engine’s acceleration. 

You will need to maintain accurate timing whenever your engine’s timing belt has been replaced or adjusted. Bad injection timing can lead to an engine misfire. It can also increase fuel consumption, reduce power, and lead to the excess production of smoke.  

Note that the consequences’ severity will depend on the timing’s inaccuracy level. If the timing is slightly off, you could have little to no issues. However, note that you will need professionals to help check your fuel injector. 

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