Maktest News, Electronic Unit Injector, EUI Injector

The Merits of an Electronic Unit Injector (EUI)

The emergence of Electronic Unit Injectors occurred due to the demand for improved power and cleaner fuel emissions, quieter operations, as well as the need for and enhanced fuel economy.

An Electronic Unit Injector, commonly abbreviated as EUI, is a unit fuel injector that is electronically controlled.

The fuel is generally delivered to the internal combustion engines of on-road or off-road vehicles or diesel-electric locomotives, and so on.

EUIs use a camshaft to deliver fuel under pressure and an engine control unit.

This is why Electronic Unit Injectors have a bit of an edge over conventional unit injectors.

The Function of an Electronic Unit Injector System

Perhaps making a general statement on how EUIs function is a little difficult because many leading companies in the engine manufacturing industry have created their own Electronic Unit Injection Systems, each having its own mechanism and function.

However, Electronic Unit Injectors are all mechanically pressurized via the use of electronic control of metering, timing, and functions.

An Electronic Unit Injection system generally consists of the following basic elements:

  • Spring-loaded Plunger & Barrel: Used to pressurize the fuel in the EUI.
  • Poppet Valve: Used to activate the needle or poppet vale fuel shaft.
  • Return Passageways: Used to ensure an efficient flow of fuel.
  • Nozzle Valve: Used to improve atomization.

By controlling fuel injection timing, these four components work together within the EUI and contribute to reduced engine emissions and, ultimately, improved engine performance.

Advantages of Using an Electronic Unit Injector (EUI)

The utilization of an Electronic Unit Injector System for fuel supply to engines has several advantages over conventional fuel injection methods.

Let’s name a few:

  1. Better Fuel Spraying under pressure
  2. Better atomization of fuel in the air
  3. Better mixing of fuel with air particles + less time to do it
  4. Increased Engine Power due to better combustion
  5. Lower fuel consumption
  6. Higher torque due to better combustion and less decline in the fuel’s hydrocarbons
  7. Lower Polluting Emissions
  8. Improved cold start of the vehicles and their warm-up and acceleration
  9. Less vehicle maintenance requirements and more reliability

The 4 Phases of EUI

Phase 1: Fill

The pump plunger moves back, and fuel is poured into the pump from the fuel supply line.

Phase 2: Spill

The pump plunger starts to descend while the valve is still open, and the fuel goes back to the return line.

Phase 3: Injection

During the pump stroke, the solenoid energizes and thus closes the spill valve. This is how the fuel is sprayed into the cylinder via the spray tip.

Phase 4: Pressure Reduction

Nearing the end of the pump stroke, the valve opens again, which allows the fuel to recirculate, thus finishing the fuel injection process.

Fuel Injection Failure

Below are possible problems that may ultimately lead to the failure of the fuel injection process.

Water Contamination

This is one of the biggest concerns because it is very common.

During the fueling process, water may enter the fuel supply, and most air can condense and fall on the cold metal walls of the fuel storage tanks or even dissolve into the fuel if it is cool.

Therefore, if water accumulates and vaporizes, it can cause a tip to blow off one of the injectors.

Water can cause problems with the injector plunges, and if it combines with the sulfur inside the fuel, together, they can form corrosive acids.

Missing Injector Tip

This is basically a consequence of the first cause of failure, which is water contamination.

As mentioned, water disrupts the function of injector plungers by displacing the lubricating diesel film surrounding injector plungers.


If dirt enters the electronic unit injector system, it can shorten the injector’s life, especially the popper/spill valve; it is the most vulnerable to dirt.

Even though filters can downsize the dirt particles to 10 microns, however, some particles are less than 10 microns in size, and these cause damage.

However, micro-glass filters can be used in EUI systems, and they can downsize the dirt particles to 2 microns with a working efficiency of 90%.

Fuel Temperature

Even though Diesel fuel cools off the injection system, the temperature of the fuel itself may vary because of the operating temperature of the engine.

As the fuel temperature rises, the fuel viscosity declines, and its ability to lubricate itself too.

When the Electronic fuel injection system operates with rising fuel temperatures, the injectors will operate at reduced internal clearances, which ultimately allows dirt and other materials to disrupt the functioning of the whole system.

Avoiding EUI Failure Through Constant Testing

In order to avoid possible system failures, Maktest has developed EUI Injector testing machinery sold worldwide to leading companies and factories across the globe.

There are over 1000 units of UTS1004 currently being used in 75 different countries.

It has an adjustable CAM stroke and a patented cam box design. It has a user-friendly interface, and most importantly, it has the technical capabilities to test from Caterpillar to Continental VDO.

If you only need the Cambox for testing electronic unit injectors and unit pump, you can get Maktest’s U1000 product. It works for EUI EUP Test Bench (Electronic Unit Injector and Unit Pump Test bench) with a power of 7.5 kW.

Electronic Unit Injector System FAQ

How do you test an electronic unit injector?

There are several Electronic Unit Injectors and Unit Pump Test bench equipment provided by Maktest, like UTS1004, U1000, and TK1022.

How do you test an electronic unit pump?

Maktest’s products UTS1004, U1000, and TK1022 are used to test not only electronic unit injectors but also electronic unit pumps.

How do you test an electronic fuel injector?

You can do a quick check by starting the engine and letting it run at a steady speed. Keep the engine running and touch the fuel injector with the end of a long metal screwdriver. Put your ear on the screwdriver at the other end. If you hear the injector click, it’s working.

How do you test an electronic diesel injector?

You should be alert for signs like smoke or a rough-running engine or if the vehicle’s diesel filter is regenerating more than usual. This is how you test your diesel injector. If any of these signs occur, then it is probably time to replace, clean, or test the engine via Maktest’s equipment.

Leave a Reply

Your email address will not be published. Required fields are marked *