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What Is Phasing in Fuel Injection Pump?

Posted by Scott Goldfarb on

A diesel vehicle's injection system provides fuel to an engine’s cylinders. However, how and when the fuel delivery is carried out may affect the car engine’s performance and sound. Here, you may ask: what is phasing in fuel injection pump, and why is it used?

Advancement in the engine’s timing speeds up the injection process. This way, the fuel delivery will occur earlier than the vehicle manufacturer’s settings. A fuel injection pump has settings that keep an equal timing between the starting and ending of the fuel injection process.

So, we will explore the meaning behind fuel injection pump phasing, common usage, and problems, as well as how it differs from calibration.

What Is Phasing in Fuel Injection Pump

Source: shutterstock.com/ Photo Contributor: Matveev Aleksandr

What Is Phasing In Fuel Injection Pump?

Technical terms in engine car parts may sound confusing and complicated. However, they are important to learn if you want to ensure your engine is working properly and don’t often experience troubleshooting problems.

Phasing involves making adjustments to the fuel injection timing accompanied by another process called calibration. Before adjusting the timing of the fuel injection, automotive mechanics focus on synchronizing the camshaft and plunger for proper fuel delivery.

However, some injection pump parts often need to be replaced with new or used ones. That may include high-pressure components, including a nozzle and an accumulator, to improve phasing accuracy for optimal engine operation.

Keep in mind the quality of pump parts depends on the supplier. You must choose a responsible diesel rebuild service that sells high-quality, durable products to ensure efficiency and long-lasting performance. For example, at Goldfarb & Associates, we offer high-quality diesel parts you may not find elsewhere.

Understanding fuel injection pumps

A diesel engine requires fuel delivery at a high pressure. Thus, all fuel injection system components must be durable enough to withstand extreme force and pressure. Also, a diesel engine's performance depends on its injection system's efficiency.

However, in order for a diesel engine to achieve superior performance, some adjustments to the system may be required. For this reason, a fuel injection pump's function is to deliver diesel to the engine’s cylinders, impacting its performance, emissions, and noise characteristics.

How Does Phasing in Fuel Injection Pump Work?

Phasing in the fuel injection pump is used to reduce torque fluctuations and gear impact noise. Increasing fuel injection pressure may lead to torque fluctuation during the engine cycle. Due to this, gear impact noise might increase. 

Torsional vibrations may also be affected by the phase difference between the engine and components, including the fuel injection pump and crankshaft. Other components relevant to phasing include the fuel injection pump’s camshaft and plunger. They can also be used to adjust and control the fuel injection timing by the engine load.

What Is the Difference Between Phasing and Calibration in a Fuel Injection Pump?

Now that you know what phasing in a fuel injection pump is, learning the meaning behind calibration is also crucial. Fuel injection pump calibration is performed to ensure the same quantity of fuel is delivered to all the cylinders of the car’s engine. 

Simply put, a diesel engine must have equal fuel quantity in each of its many cylinders through a plunger. When all of this is set and done, the speed lever is moved to the maximum fuel delivery as specified by the manufacturer.

The process of calibration is usually carried out before the fuel injection pump has been repaired or rebuilt. Then, the phasing procedure with timing adjustments can be performed, and the manufacturer’s recommended speed can be safely altered.

Overall, phasing synchronizes the fuel injection pump with the engine's crankshaft to inject fuel correctly in the engine cycle. On the other hand, calibration adjusts the various parameters of the fuel injection system to optimize fuel delivery and engine performance.

Common Phasing Methods

The basic rule of fuel injection includes the right amount of fuel being injected at a specified time to satisfy engine power demands. Fuel needs time to burn. Yet, to burn correctly, fuel must be injected at an appropriate point with phasing.

Although many different systems are used to control the fuel injection process, mechanical and electronic are the most common. Let’s learn how these approaches lead to different phasing methods in a fuel injection system.


The fuel injection process in diesel engines is carried out through a compression stroke. In a mechanical system, the fuel injection pump must provide enough pressure to the fuel charge. The fuel is then passed to the high-pressure injectors into the combustion chamber, igniting and producing the power stroke.


Electronic unit injectors can successfully replace some high-pressure fuel system mechanical components. They substitute the injection pump, fuel lines, and nozzles from mechanical engines with electronically triggered unit injectors in each cylinder. 

Electronic phasing delivers low-pressure fuel to each injector through the cylinder head. And, fuel is passed through each injector with enough pressure and released into the cylinder with a plunger.

Importance of Phasing for Engine Performance

Phasing refers to the time in the engine cycle, specifically the compression and expansion strokes, in internal combustion. A change in phasing may affect the combustion duration and engine performance.

Moreover, timing alterations of the crankshaft and the opening and closing motions of the engine’s valves may result in improved fuel efficiency, power output, and emissions control. These types of adjustments can be done by using a timing phaser.

Troubleshooting Phasing Issues

Improper phasing in the fuel injection pump may lead to various issues. If the crankshaft is incompatible with the camshaft, the valves may open or close at the wrong time. This troubleshooting phasing issue may result in poor combustion timing, reduced engine power, decreased fuel efficiency, and increased emissions.

The engine gives clear symptoms of failure that can be easily identified. These include engine misfires, vibrations and noise, oil leaks, difficulty starting the engine, and increased fuel consumption connected to the crankshaft’s condition.

Newer engines use modern technologies such as variable valve timing and camshaft phasers to ensure proper phasing. These systems can adjust the camshaft timing and establish control over the valve opening and closing motions. 

Altogether, the engine can achieve better performance and improved fuel economy by optimizing the phasing of the crankshaft and camshaft.

Troubleshooting Phasing Issues

Source: shutterstock.com/ Photo Contributor: MR.TEERASAK KHEMNGERN


What is phasing in fuel injection pump? Phasing is crucial for improving a diesel engine's efficiency. This process must be adequately handled with the help of a reputable supplier and professional mechanics. 

So, we offer remanufactured or new fuel injection components, allowing a vehicle to achieve top performance. All you have to do is visit or contact us!


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