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Harley Davidson Fuel Injection Problems: Skip The Forums

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Harley Davidson motorcycles have come a long way from the days of carburetors, and fuel injection systems have become the standard for modern bikes. However, with technological advancements come new challenges, and the fuel injection system on Harley Davidson motorcycles is no exception. In this comprehensive guide, we will explore some common Harley Davidson fuel injection problems, their symptoms, and potential solutions to keep your bike running smoothly so keep reading and lets get to it!

Looking for a quick fix? Try this: The Best Fuel Stabilizer for Harley Motorcycles Revealed

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1. Symptoms of Fuel Injection Problems

a. Poor Acceleration

One common symptom of a fuel injection problem is poor acceleration. If your Harley is struggling to pick up speed or feels sluggish, it could be due to a fuel injection issue.

b. Misfires and Backfires

Misfires and backfires are another sign of fuel injection problems. If your bike’s engine is not running smoothly, and you hear popping or backfiring noises, it could be an indication of a fuel delivery issue. Keep an eye on the idle speed as well. Depending on the circumstances the bike can develop a high idle or a low idle.

Related: Harley Speed Sensor Symptoms Get Revealed (+Easy Fixes)

c. Reduced Fuel Mileage

A decrease in fuel mileage is another indicator of potential fuel injection problems. If you notice that your Harley is consuming more fuel than usual, it could be due to an issue with the fuel injection system.

d. Fouled Spark Plugs

Fouled spark plugs can also be a symptom of fuel injection problems. If you notice that your spark plugs are blackened or covered in deposits, it could be due to an improper fuel mixture caused by a malfunctioning fuel injection system.

e. Engine Stalling

If your Harley’s engine stalls, wont idle, or has difficulty starting, it could be a sign of fuel injection problems. This can be caused by a variety of issues, including a malfunctioning throttle position sensor or a clogged fuel injector.

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2. Causes of Fuel Injection Problems

a. Faulty Fuel Injectors

One common cause of fuel injection problems is faulty fuel injectors. Over time, fuel injectors can become clogged or damaged, leading to poor fuel delivery and engine performance issues.

b. Malfunctioning Throttle Position Sensor

The throttle position sensor is responsible for monitoring the position of the throttle and relaying this information to the engine control unit (ECU). If this sensor is malfunctioning, it can cause fuel injection problems and poor engine performance.

c. Damaged or Leaking Fuel Lines

Damaged or leaking fuel lines can also cause fuel injection problems. If fuel is not being delivered to the injectors properly, it can result in poor engine performance and fuel inefficiency.

d. Faulty Engine Control Unit (ECU)

The ECU is responsible for controlling the fuel injection system and ensuring that the proper amount of fuel is delivered to the engine. If the ECU is malfunctioning, it can cause a variety of fuel injection problems, including poor acceleration, misfires, and reduced fuel mileage.

e. Clogged Fuel Filter

A clogged fuel filter can also cause fuel injection problems. If the fuel filter is not allowing fuel to flow freely to the injectors, it can result in poor engine performance and fuel inefficiency.

Related: Will Bad Gas Cause A Misfire? Yes, and No [Find Out]

Other Common Harley Davidson Issues:

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3. Diagnosing Fuel Injection Problems

a. Visual Inspection

One of the first steps in diagnosing fuel injection problems is to perform a visual inspection of the fuel system. Check for any visible damage to the fuel lines, injectors, and other related components.

b. Check Engine Light

If your Harley’s check engine light is illuminated, it could be an indication of a fuel injection problem. You can use a diagnostic tool to read the trouble codes stored in the ECU, which can help pinpoint the issue.

c. Fuel Pressure Test

Performing a fuel pressure test can help you determine if there is an issue with the fuel delivery system. This test involves connecting a fuel pressure gauge to the fuel system and observing the pressure readings while the engine is running.

d. Injector Flow Test

An injector flow test can help you assess the performance of your fuel injectors. This test involves measuring the amount of fuel that is being delivered by each injector over a specified period of time.

e. Diagnostic Tools

Using diagnostic tools, such as a scan tool or multimeter, can help you diagnose fuel injection problems by monitoring various sensor readings and checking for any inconsistencies or malfunctions.

Read next: Harley Automatic Compression Release Problems (FIXED!)

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4. Fixing Fuel Injection Problems

a. Cleaning Fuel Injectors

One potential solution to fuel injection problems is to clean the fuel injectors. This can be done using a fuel injector cleaning kit or by removing the injectors and cleaning them manually.

a2. How to Remove and Clean Harley Fuel Injectors

Here’s a brief guide:

  1. Disconnect Battery: Ensure safety by disconnecting your motorcycle’s battery.
  2. Remove Seat and Gas Tank: Follow your Harley’s manual for proper removal.
  3. Locate and Disconnect Injectors: Find the fuel injectors on the fuel rail and disconnect them.
  4. Clean Injectors: Soak and clean the injectors using a commercial injector cleaner or a mixture of cleaner and gasoline. Use a soft brush for the tips if necessary.
  5. Rinse and Dry: After cleaning, rinse the injectors with clean gasoline and allow them to dry.
  6. Reinstall Injectors: Carefully place the injectors back into the manifold, ensuring a proper fit.
  7. Reassemble Bike: Reattach the fuel line, gas tank, and seat.
  8. Reconnect Battery: Reattach the battery, starting with the positive terminal.

b. Replacing Faulty Components

If you have determined that a specific component, such as a fuel injector or throttle position sensor, is causing the problem, you may need to replace the faulty part.

c. Checking and Adjusting Throttle Cables

Ensuring that your throttle cables are properly adjusted can help prevent fuel injection problems. If the cables are too tight or too loose, it can cause issues with the throttle position sensor and fuel delivery.

d. Updating the Engine Control Module (ECM)

In some cases, updating the ECM’s software may help resolve fuel injection problems. This can be done by a Harley Davidson dealership or by using an aftermarket tuning device.

e. Replacing the Fuel Filter

If you suspect that a clogged fuel filter is causing your fuel injection problems, you should replace the filter to ensure proper fuel flow to the injectors.

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5. Preventing Fuel Injection Problems

a. Regular Maintenance

Performing regular maintenance on your Harley can help prevent fuel injection problems. This includes changing the oil, replacing the air filter, and checking the fuel system components for wear or damage.

b. Using Quality Fuel

Using high-quality fuel can also help prevent fuel injection problems. Poor-quality fuel can cause deposits to build up in the injectors, leading to clogging and poor engine performance.

c. Fuel Additives

Using fuel additives, such as fuel injector cleaners, can help keep your fuel injection system clean and functioning properly. Be sure to follow the manufacturer’s recommendations when using these products.

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Upgrading Fuel Injection Systems

If you’re looking to improve the performance of your Harley Davidson’s fuel injection system, there are several aftermarket options available. Some popular upgrades include:

a. Performance Injectors

Upgrading to performance fuel injectors can help improve your bike’s power and throttle response. These injectors are designed to provide a more precise fuel delivery, resulting in better combustion and increased horsepower.

b. EFI Tuning Devices

EFI tuning devices, such as the Power Commander or ThunderMax ECU, allow you to customize the fuel maps and other settings for your Harley’s fuel injection system. This can help improve performance and fuel efficiency, as well as accommodate other performance modifications. From personal experience, I would recommend avoiding the Vance and Hines FP4 however.

Related: Annoying Vance and Hines FP4 Problems To Be Aware Of

c. Upgrading to a Complete Aftermarket EFI System

For those looking for a complete overhaul of their fuel injection system, there are complete aftermarket EFI systems available, such as the S&S Cycle EFI system or the Daytona Twin-Tec system. These systems offer a higher level of customization and performance compared to the stock Harley Davidson EFI system.

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Fuel injection problems can be frustrating for Harley Davidson owners, but with the right knowledge and tools, many of these issues can be diagnosed and resolved. By understanding the symptoms and causes of fuel injection problems, you can take the necessary steps to keep your bike running smoothly and efficiently. Regular maintenance, using quality fuel, and upgrading your fuel injection system can all help prevent and address fuel injection problems on your Harley Davidson motorcycle.

Customer Complaints

Here are some direct user quotes as customer complaints regarding Harley Davidson fuel injection problems:

  • “Rear injector replaced about 8k ago, now the symptoms are back again – OK acceleration, but misses during steady speed, fuel mileage down, backfires and pops.”
  • “Took the plugs out today, the rear plug is fouled. Think it’s just a bad injector (again) or could it be the ECM?”
  • “5 hours to diagnose a bad injector? He should turn in his tools and become a cook.”


The information provided in this article is for informational purposes only and should not be considered professional advice. Always consult a qualified technician or mechanic before attempting any repairs or modifications on your motorcycle.

What To Do When Your Fuel Injected Harley Wont Start

When you’ve got a fuel-injected Harley that just won’t roar to life, it’s easy to feel frustrated. Don’t worry, though! We’ve got your back with some handy tips to get you back on the road:

  1. Battery woes: If your bike’s battery is weak or the connections aren’t secure, you might have some trouble getting it started. Double-check that everything’s in order, and don’t be shy about charging that battery!
  2. Fuses: Sometimes, it’s the little things that make all the difference. Take a peek at your fuse box, and see if any fuses need replacing before you try to start your motorcycle again.
  3. Fuel pump issues: When you turn on the ignition, you should hear the fuel pump working. If not, there could be a problem with the pump itself or its connections. Investigate further to pinpoint the root cause.
  4. Fuel delivery: Make sure your tank isn’t empty, and don’t forget to check for any blockages or leaks in your fuel lines. You can’t go far without fuel, after all!
  5. Spark plugs: A fouled or damaged spark plug can cause a world of trouble. Give them a thorough inspection and replace them if needed, to ensure a smooth, powerful ride.
  6. Diagnostic trouble codes (DTCs): Get the scoop on what’s happening with your Harley by accessing its DTCs. These codes can offer valuable intel about potential issues, and you might not even need special tools to retrieve them!

What Year Did Harley Davidson Go To Fuel Injection?

In the year 1995, Harley-Davidson took a bold step by introducing fuel injection to its Softail line, beginning the journey of phasing out carburetors. As time marched on, this innovative technology found its way into more and more Harley models, becoming a staple for the legendary brand.