Top 10 Symptoms Of Bad Fuel Pump In Motorcycle: Quick Repair

Top 10 Symptoms Of Bad Or Failing Fuel Pump In Motorcycle

The motorcycle fuel pump plays a crucial role in supplying fuel to the engine. The fuel delivery process by the fuel pump helps the motorcycle to start and run properly.

There are two types of fuel pumps used in motorcycles. Electric fuel pumps and mechanical/vacuum-type fuel pumps. The symptoms of failing or bad fuel pumps apply to both these types.

Here are the Top 10 most common symptoms of a bad fuel pump that causes poor fuel delivery in motorcycles.

  1. Taking Longer Engine Cranking Time
  2. Sudden Power Surge While Riding
  3. Difficulty While Starting The Motorcycle
  4. Motorcycle Engine Sputter Or Hesitation
  5. Bad Motorcycle Idling Condition
  6. Whining Noise Because Of Bad Fuel Pump Condition
  7. Poor Acceleration & Performance Of Motorcycle
  8. Motorcycle’s Engine Stalling
  9. Low Mileage Due To Improper Fuel Delivery
  10. Motorcycle Engine Failure Or Overheating

Today we are going to look into each symptom in detail and how to successfully repair a bad fuel pump.

By the end of this article, you will be able to know if your motorcycle’s fuel pump is bad, does it needs replacement, and what will be the cost of replacing it.

Now let’s know about the signs of a bad fuel pump in detail and how it can harm your motorcycle.

1. Taking Longer Engine Cranking Time

A faulty fuel pump, whether mechanical or electric, leads to irregular fuel supply to the cylinders through the fuel injector or carburetor.

The fuel pump moves fuel from the fuel tank to the fuel injector in new bikes and through carburetors in ones, which then sprays the right air-fuel mix into the engine.

So longer engine cranking time in motorcycles is also caused by the fuel pump failing to prime on its initial attempt.

Irregular fuel supply also causes prolonged starting times or prevents the engine from starting altogether.

So read this article on Why Motorcycle Fuel Pump Not Priming: Easy Fix.

As a result, the fuel isn’t pressurized properly, leading to longer starting times for the motorcycle’s engine. Sometimes, you may need to press the starter button repeatedly or for an extended duration.

2. Power Surging Suddenly While Riding

For a motorcycle to provide consistent power delivery, it needs a continuous flow of proper air-fuel mixture.

For steady cruising speed, the ideal air-fuel mixture range is typically between (14.7:1 and 15.1). Meaning for every 1 gram of fuel, around 14.7 grams of air is required.

The motorcycle experiences a sudden power surge because the motor of the fuel pump and fuel line develops irregular resistance.

This simply indicates that the fuel intake and pressurization process, from the tank through the inlet valve to the engine via the outlet valve, is inconsistent.

A faulty spring inside a mechanical/vacuum-type fuel pump causes excess fuel to be supplied to the engine’s cylinder, resulting in sudden bursts/surges of power and higher acceleration.

3. Difficulty While Starting The Motorcycle

The state of a bad fuel pump creates difficulties while starting the motorcycle. A faulty fuel pump with a bad/damaged fuel pump relay will cause difficulty in starting the motorcycle

A faulty fuel pump relay will fail to receive and pass the power to the fuel pump motor. Irregular or inefficient supply of fuel will be the result of a damaged fuel pump relay and the fuel pump itself.

So difficulty while starting the motorcycle is evident and might need several tries for a successful motorcycle start.

4. Motorcycle Engine Sputter Or Hesitation

Engine sputtering is one of the clear-cut symptoms of a bad fuel pump. While riding a motorcycle this situation can be upsetting and frustrating.

Motorcycle sputter simply means the supply of fuel to the engine is not linear but rather sporadic.

This causes the motorcycle to suddenly lose power resulting in no throttle response condition.

So if you experience your motorcycle having a hard time maintaining constant speed and losing power while accelerating, then your motorcycle is sputtering.

The motorcycle sputtering or hesitation issue is a direct symptom of a bad fuel pump.

If you want to know the causes & symptoms behind motorcycle sputtering and how to stop it to avoid some serious damage to the engine, then please check the article. ( Click The Underlined Link To Read )

5. Bad Motorcycle Idling Condition

A motorcycle idles well when the fuel pump consistently supplies enough fuel to the injector or carburetor. The correct air-fuel mixture ratio while motorcycle idling is around 10:1-12:1.

So the motorcycle idles poorly when the faulty fuel pump fails to deliver enough fuel to the engine with a wrong air-fuel mixture.

If you don’t rev the engine to maintain idle, the motorcycle will struggle to stay running and may shut off quickly.

6. Whining Noise Because Of Bad fuel Pump Condition

Typically, the motorcycle fuel pump sits near the fuel tank. The noise from the fuel pump will be noticeable and easy to get your attention.

A faulty pump with broken moving parts such as the diaphragm, spring, or solenoid can cause a whining noise.

It’s a certified sign to replace the bad fuel pump with a new one immediately, as it is a major part of the motorcycle’s fuel system.

7. Poor Acceleration & Performance Of Motorcycle

As we discussed earlier, a failing motorcycle fuel pump will contribute to inconsistent fuel delivery in the motorcycle.

Poor acceleration is an obvious sign of a bad fuel pump where the power drop is pretty significant and the throttle response is delayed.

Clogged Fuel lines will also cause inconsistent fuel delivery to the engine.

This drop in power is consistent and happens pretty often. The power cut-off may happen at various RPM ranges ( ex. 3000k – 4000k Rpm or 5000k – 6000k Rpm ).

Motorcycles will struggle to reach high speeds quickly and may find it challenging to maintain a consistent RPM.

8. Motorcycle’s Engine Stalling

An adequate amount of fuel supply to the engine is necessary for the motorcycle to run and stay idle.

And proper combustion and ignition should take place to start the motorcycle.

So a bad/malfunctioning fuel pump will not be even able to pressurize the fuel in the motorcycle to get it started or cause a stalling issue while riding.

9. Low Mileage Due To Improper Fuel Delivery

The pump pulls fuel from the tank and sends it to the carburetor or fuel injector through the fuel pump’s inlet and outlet valves.

The fuel pressure regulator regulates the flow of fuel to the engine.

Malfunctioning in fuel pump valves, fuel pressure regulator, or sensors in an electric fuel pump can cause fuel delivery problems to the engine cylinder.

This malfunction causes more fuel to be sent to the engine, resulting in overall low mileage for your motorcycle.

10. Motorcycle Engine Failure Or Overheating

A motorcycle runs well with a steady fuel flow to the engine. If the air-fuel mix is too lean or rich, your motorcycle behaves differently.

Defects in these parts of the fuel pump or pressure regulator change the air-fuel mixture ratio ( less fuel more air or Vice versa ), which causes the engine to run hot and overheat.

The lean air-fuel mixture inside the engine burns slowly ) resulting in exposure to heat for a prolonged time.

So, a bad fuel pump will cause the motorcycle to overheat.

Now you will know how to know and find these symptoms in your motorcycle and if needed you can replace your bad fuel pump with a brand new one.

How To Repair A Bad Fuel Pump?

Replacing faulty parts of the fuel pump such as the pressure regulator, sensors, or broken O-rings/washer/nut will fix a bad fuel pump.

Cleaning the residue from the fuel pump filter, fuel strainer, and fuel lines will make the fuel pump work properly.

If the fuel pump motor is damaged, then replacement of the whole fuel pump assembly kit will cost around $400-$100 Dollars (service charges may vary depending on service stations ).

Parts of the fuel pump will range from $40-$200 Dollars. Keep in mind that prices of the parts and whole fuel pump kit will vary from motorcycle to motorcycle.

How long do motorcycle fuel pumps last?

Motorcycle fuel pump last for 90,000 – 100,000 Miles/ 1,44,840 – 1,60,934 Kilometers in a well maintained regularly serviced motorcycles. 

Service cleaning of fuel pump includes fuel regulator, fuel strainer, and O-rings, and you can refer to the owner’s manual while disassembling and cleaning other parts of the pump.

You can use any cleaning chemical solvent ( Contact Cleaner ), I have found Maxima Contact Cleaner to provide the overall thorough cleaning process, leaving no residue or sediments (dirt deposits) behind.

But avoid products that have acetone in them cause it will damage your fuel strainer’s fabric material.

Improper service intervals and running motorcycle on significantly low amounts of fuel will cause the fuel pump to work harder to push the fuel to the engine.

A well-maintained fuel pump won’t need replacement, just a thorough cleaning and service ritual is a must-follow procedure.


Now you know the top 10 most common symptoms of a bad pump in the motorcycle which will help you know if you need to replace it or not.

If the fuel pump is severely rusted, don’t attempt to clean and reuse it because it could damage your motorcycle.

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