How to Replace Fuel Injectors on Harley-Davidson


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How To Replace Fuel Injectors On Harley Davidson

Do you own a Harley-Davidson bike, and you are looking to replace the fuel injectors but don’t know how to? If yes, then you are definitely in the right place.

Replacing fuel injectors on Harley-Davidson bikes is quite easy as long as you know the right steps. The entire process is effortless and involves disconnecting the fuel line, removing the mounting hardware, and removing the old fuel injector. After that, you should clean the mounting location, install the new fuel injector, reconnect the fuel line, and test the new fuel injector.  Gather the necessary tools, and you’ll be able to do it within a matter of minutes.

In this article, you will get to know all about the fuel injector systems, how to replace fuel injectors on Harley-Davidson, how to test the new fuel injector, and more. Continue reading to get all the answers that you are looking for.

What is the Electronic Fuel Injection System?

In simple terms, an electronic fuel injection (EFI) system is essentially a computer-controlled fuel delivery system. The electronic control unit (ECU) will read different sensors located on the vehicle. It’ll also make the determination of how much fuel should be allowed to the engine depending on this information. The computer will open and close the injectors, which will allow gasoline into the engine depending on the sensor inputs and the fuel map programmed into the system.

The different sensors (engine temperature, RPM, air temperature, manifold pressure, throttle position, crankshaft position, and more) will provide information on the operating conditions and load on the engine. 

One of the major differences between fuel injection systems will be how the bike senses the amount of load placed on the engine. The load can be sensed by how far the rider has twisted the throttle and Manifold Absolute Pressure). The EFI systems that sense the engine load by using the throttle or throttle position sensor will be referred to as an Alpha-N system. EFI systems that sense engine load by the use of a MAP sensor will be referred to as a Speed-Density system. 

Harley-Davidson is a brand that has made use of both types of EFI systems on its bikes. While many of the sensors are the same in both types of systems, there’s a significant difference in the way the two systems determine what the load on the engine actually is.

The Magneti-Marelli system was used on the Twin Cam FLH and EVOs until 2001 while Buell XL engines also used an Alpha-N EFI system. On these motorcycles, load sensing will be determined by the throttle position. The newer Delphi EFI system on the current Twin Cam engines is essentially a Speed Density system. This system will determine the engine load depending on the intake manifold vacuum.

Benefits of Different Types of Fuel Injection Systems

There are benefits to each of the three types of EFI systems. The choice of systems will be depended on the type of vehicle and its usage. When considering the Harley-Davidson Magneti-Marelli EFI system, the simplicity of using the throttle position sensor for determining engine load will be the determining factor for using the first OEM EFI system.

A Speed Density EFI system will require a steady vacuum system from the MAP sensor for the ECU to determine the fuel mixture accurately. If you have tried to read the vacuum gauge connected to the V-twin engine and watched the needle bounce, you will better understand why a Speed Density EFI system wasn’t the first choice for Harley-Davidson engines with long-duration cams or individual intake runners. Despite what might seem like an insurmountable problem with creating steady vacuum readings, there are many mechanical and electronic ways of calming the MAP readings for the ECU to use.

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The Delphi EMS system will use the manifold pressure from the Harley-Davidson intake. This will allow the bike to determine the load on the engine more accurately based on the vacuum in the manifold instead of the position of the throttle. The Delphi unit will offer a level of sophistication and the ability to customize fuel maps in the field.

How to Replace Fuel Injectors on Harley-Davidson

Fuel injectors are an important component of your bike’s fuel system. It’ll be responsible for delivering a more precise amount of fuel to the engine. Over time, fuel injectors will become clogged or fail because of normal wear and tear. When that happens, it’ll be important to replace the faulty injector for ensuring that the engine is running effectively and efficiently. 

You will have to know how to replace the fuel injector on your bike. Gather the tools and materials, identify the fuel injector, and replace the fuel injectors. Once you know the instructions, you will be able to replace the fuel injector confidently and safely.

Step 1: Gather the tools and materials

Before you get started, you should ensure that you have these tools and materials –

  • New fuel injector 
  • Socket set
  • Fuel line disconnect tool
  • Screwdriver set
  • Wrench set
  • Rags

You might also require additional tools and materials specific to your bike. It’ll be a good idea to consult the owner’s manual or a repair manual for these instructions.

Step 2: Identifying and locating the fuel injector

The first step when replacing the fuel injector will be identifying which one has to be replaced. It can be done by visually inspecting the injectors and then looking for any signs of wear or tear like leaks or cracks. Alternatively, you can make use of diagnostic tools for pinpointing the faulty injector. Consult the owner’s manual or the repair manual for specific instructions on how to use diagnostic tools on your specific bike.

Once you have identified the faulty fuel injector, the next step would be to locate it.  In most bikes, the fuel injectors will be located near the intake manifold in the engine compartment. It might be hidden by other components, so you might have to remove a few parts for accessing them. 

Step 3: Prepare your bike for fuel injector replacement

Before you start replacing the fuel injector, you will have to prepare your Harley-Davidson bike. First, you should ensure that you’ve got enough space to work. If needed, you should lift the vehicle using a jack and secure it using jack stands. Then, you should gather all the tools and materials and keep them within easy reach.

Next up, you will have to relieve the pressure in the fuel injection system. This is essential for preventing the fuel from spraying out when you are removing the fuel injector. Consult the owner’s manual or the repair manual for instructions on how to relieve pressure in the fuel system of your bike. You might have to use a fuel pressure gauge for checking the pressure and releasing it as needed.

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Once the pressure in the fuel system is relieved, you will be ready to start the fuel injector replacement process. 

Step 4: Disconnect the fuel line

Once you have identified ad located the fuel injector, it will be time to remove it. 

The fuel injector will be connected to the fuel line, so you will have to disconnect it. Use the fuel line disconnect tool for loosening the clamp or clip that is holding the fuel line in place. After that, pull the fuel line away from the fuel injector gently. Be careful that you do not damage the fuel line or spill any fuel.

Step 5: Remove the mounting hardware

The fuel injector is generally held in place with screws or bolts. Use the appropriate wrench or socket for removing the mounting hardware and set it aside.

Step 6: Remove the old fuel injector

Once you have removed the fuel line and mounting hardware, the old fuel injector will be loose. Carefully, you should pull it out of the mounting location while taking care that you aren’t damaging any surrounding components. In case the fuel injector is stuck, you might have to gently wiggle it back and forth for loosening it.

Once the fuel injector is removed, you should set it aside and then proceed forward.

Step 7: Clean the mounting location

Once the old fuel injector is removed, it will be time to install the new fuel injector. 

Before installing the new fuel injector, it’ll be important to clean the mounting location. Use a clean rag for wiping away any dirt or debris that might have accumulated. It will help you ensure that there’s a proper seal and prevent debris from entering the fuel system.

Step 8: Install the new fuel injector

Carefully, you should insert the new fuel injector into its mounting location while ensuring that it is seated properly. 

After that, replace the mounting hardware and then tighten it by making use of an appropriate wrench or socket.

Step 9: Reconnect the fuel line

Once the new fuel injector has been installed, it’ll be time to reconnect the fuel line. Use the fuel line disconnect tool for securely attaching the fuel line to the fuel injector. After that, double-check to ensure that the fuel line is properly secured and that there are no leaks.

Step 10: Test the new fuel injector

Before you start riding your Harley-Davidson bike, it will be important to test the new fuel injector. It will help you ensure that it is working properly. Consult the owner’s manual or repair manual to get specific instructions on how to test the new fuel injector on your bike. You might have to use a diagnostic tool or start the engine before observing the fuel system for any issues.

If the fuel injector has passed the test, you will be ready to move to the next step. If not, you might have to troubleshoot the issue or repeat the installation process.

How to Test a New Fuel Injector

Once you have installed the new fuel injector, it will be important to test it to ensure that it is working properly. You need to follow these steps for testing your new fuel injector.

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Step 1: Check for any leaks

The first step to testing the new fuel injector would be to check for any leaks. Start the engine and then allow it to run for a while. After that, carefully inspect the fuel injector and the surrounding area for any potential leaks. In case you spot a leak, you should shut off the engine and then tighten the mounting hardware and fuel line as necessary. After that, you should test the fuel injector again. 

Step 2: Check the fuel pressure

Next up, you will want to check the fuel pressure to ensure that it is within the proper range. Consult the owner’s manual or a repair manual for the proper fuel pressure range for your bike. Make use of a fuel pressure gauge for checking the fuel pressure and then compare it to the recommended range. If the fuel pressure is too low or too high, there might be an issue with the new fuel injector system as a whole.

Person Checking Fuel Pressure Of Harley Davidson Motorcycle

Step 3: Test drive your bike

The last step in testing the new fuel injector would be to take your Harley-Davidson bike for a test drive. Pay close attention to how the engine is running, while also listening for any unusual noises. In case the engine is running smoothly and there aren’t any issues, it means that the new fuel injector is installed successfully. If you notice any issues, you might have to troubleshoot the issue or repeat the entire installation process.

By following these steps, you will be confident that the new fuel injector is working properly and that your Harley-Davidson bike is running efficiently.


Can I replace the fuel injector of my bike on my own?

Yes, it is possible. However, it isn’t going to be an easy process to replace a fuel injector on your own, so you should hire a professional at all times. Even if you’re looking to spend less, it’ll still be a good idea to let an expert do this job. You can learn to clean fuel injectors properly so that they last a bit longer.

How will I know if my fuel injectors need replacing?

You can find out if it is time to visit your local mechanic and replace the defective fuel injectors if you experience any of these issues – engine stalling or rough idle, bad fuel economy, engine misfires, engine light not working properly, RPM needle starts dancing, among others.

What is the average lifespan of a fuel injector?

Fuel injectors have an atomizing nozzle for distributing the fuel evenly for optimal combustion and efficiency. These days, a bike will typically use one fuel injector per cylinder and come with a lifespan between 50,000 and 100,000 miles or around 80,000 and 160,000 kilometers.

Can I clean my fuel injectors?

When the fuel injector is clogged, it’ll require a concentrated cleaning for resolving the issue. It can be done by a qualified mechanic or if you know how to navigate the engine of your bike, you can do things yourself. For starters, you will have to invest in a fuel injector cleaning kit.

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