Category Archives: HOW TO’S

How to diagnose fuel system issues & perform basic maintenance

5 Ways To Bulletproof Your Fuel System

5 Ways To Bulletproof Your Fuel System

Outdoor recreation is booming, which means more people are using their Powersports vehicles. Motorcycles, dirt bikes, ATVs, UTVs/Side-By-Sides, snowmobiles, and personal watercraft are racking up hours across the United States as new riders and families join in on the fun. Motorcycle sales alone were up nearly 10 percent in 2021, hitting their highest levels in 15 years. 

All that time out on the road, trail, or water does add up, and responsible owners know that to get the most out of our vehicles, they need to keep up with regular maintenance. Even the most diligent owners and DIY mechanics overlook their fuel systems until there is a problem. 

We’re going to go over five easy ways to bulletproof your fuel system and ensure it’s in good working order, giving you peak performance, fuel mileage, and reliability. Don’t think these tips are exclusive to your motorcycle, quad, or UTV — these maintenance suggestions apply to any car, truck, or RV equipped with Electronic Fuel Injection (EFI). 

Quantum Fuel Systems is the authority in high-quality direct OE replacement fuel system components. All QFS-branded parts are backed by an industry-leading lifetime warranty and are designed to meet or exceed OEM quality. Visit our catalog for all your fuel system needs.

1. Keep Your Fuel Tank Full

This is one of the most straightforward tips of the bunch and applies to any standard in-tank fuel pump conveniently located inside your fuel tank. In-tank fuel pumps are constantly submerged in liquid fuel, helping lubricate and cool one of the hardest working components in your fuel system.

Radiant heat from the engine and the fuel pump’s electric motor will increase fuel temperature as your fuel load drops, putting more stress on the fuel pump and causing it to work harder, leading to premature failure.

While today’s gas prices certainly aren’t making things easy for consumers, one of the simplest ways to maintain the health of your fuel pump is never run on empty. Always try to stay above ¼, and your fuel pump will thank you for it. 

2. Don’t Fill Up When The Fuel Delivery Truck Is At The Gas Station

We know that this suggestion might sound like an urban myth, but there is nothing subtle about how a tanker truck dispenses fuel into gas station holding tanks. Thousands of gallons of fuel are dumped into a tank rapidly, stirring up sediment, debris, and even water resting at the bottom.

None of that material is suitable for your fuel system, and it’s best to let the sediment settle before filling up at that station.

3. Inspect Or Replace Filters And Strainers

Filters and strainers are the first and last words in protecting your fuel system. Without them, harmful particulates can mix with a sticky fuel remnant known as gasoline varnish, wreaking havoc on the precision components found in the fuel system and engine. Clogged or damaged filters and strainers can lead to performance loss and premature wear on your internal components.

The first line of defense your fuel system has is a fuel pump strainer that prevents sand, dirt, and foreign objects from clogging or damaging parts. Once a strainer has absorbed all the material it can, it will restrict flow, which puts unnecessary strain on the fuel pump. 

Fuel filters serve the same purpose as a strainer and are typically further up in the fuel system chain. Filters defend engine components, such as your fuel injectors and sensors, from anything that manages to get past the fuel pump strainer.

A clogged filter is detrimental to proper fuel flow, and foreign objects are equally harmful to the rest of your fuel system, clogging small passages and causing performance loss or outright mechanical problems.

Always remember that street-focused motorcycles, cars, and trucks will have much higher service intervals than anything off-road oriented. The harsher off-road environment can quickly introduce dust, dirt, and debris into the fuel system, making maintenance schedules far more frequent on dirt bikes, ATVs, and UTVs/Side-By-Sides.

Be sure to reference your model-specific manual for exact mileage/hour figures. Our complete line of filters and strainers are designed to withstand harsh fuel additives and ethanol-based gasoline, ensuring filtration and performance.

4. Clean Your Injectors

Fuel injectors do precisely that: Inject fuel into the engine throttle body or cylinder, allowing a precise amount of atomized fuel to be delivered for proper combustion. Injectors are electronically controlled valves operated by a solenoid that must open and close with extreme accuracy.

Over time, deposits can restrict their spray pattern, causing symptoms like performance loss, decreased fuel economy, rough idle, and misfires. 

Cleaning injectors do not apply to low-mileage/low-hour vehicles unless they’ve sat unused for long periods. Any late model or high-mileage vehicle can benefit from a thorough injector cleaning.

There are plenty of aftermarket tools, solvents, and fuel additives to help clean your injector system. These products remove varnish, build-up, and deposits from small passages, allowing the injector spray pattern to function as intended.

The most effective way to clean any delicate precision component is using ultrasonic cleaning tools. At-home mechanics can purchase specialized tools, but many authorized service shops have the equipment to perform this task.

Ultrasonic cleaning uses high-frequency sound waves transmitted through a liquid to scrub and clean surfaces through a process known as cavitation. These tools are incredibly adept at removing build-up, oils, and other deposits that might obstruct the spray pattern. 

If you find that your injectors are beyond repair, QFS sells direct replacements from reputable brands such as Bosch, Injector Dynamics, RC Engineering, and Siemens Deka. We also stock PnP adapters and wiring harnesses built to fit seamlessly with their respective fuel injector.

5. Maintain Electrical Components

Electrical gremlins are tough, especially when you’re out having fun on your bike, UTV/Side-By-Side, or personal watercraft. Inspecting and double-checking electrical connections is as crucial as changing fluids according to cited service intervals, although many owners don’t make it part of their routine. 

Loose or damaged connectors and wiring can lead to problems beyond intermittent issues. These bad connections could lead to a total failure of a fuel pump, pop fuses or relays, and leave you stranded.

During your routine maintenance, make it a habit to inspect all electrical connections, especially those on off-road oriented vehicles that are subject to running in dirty environments and taking lots of abuse. 

It’s also advisable to test critical electrical systems with a voltage meter to detect problems before they cause harm. While you’re there, hit the electrical connections with some contact cleaner to clean the conductive surfaces.

Lastly, those doing long-distance rides or drives should always look at the most common fuses and relays in their fuse box and carry a spare.

At the most basic level, ensuring your battery is healthy and fully charged is a good place to start. Depending on your charging system, a weak battery can reduce fuel pressure and create lean conditions.

Always keep batteries maintained with a modern “smart charger” that not only maintains a full charge but reconditions your battery and provides a long service life.  

Have Any Questions? Give Quantum Fuel Systems A Call Today!

Quantum Fuel Systems is open Monday through Friday, 8:00 a.m. to 5:00 p.m. PT. We are happy to assist our customers over the phone, or you can browse our extensive catalog. Have any technical questions? Our trained support team will get back to you with answers.

Breaking Down Fuel Pump Terminology: EFI, E85, LPH, Small Parts, and More

Breaking Down Fuel Pump Terminology: EFI, E85, LPH, Small Parts, and More

Navigating the world of fuel systems shouldn’t be difficult, especially when you’re simply trying to order quality parts for your machine. When it comes to fuel pumps, there is quite a bit of common terminology, whether you’re talking about automotive, motorcycle, ATV, UTV/Side-By-Side, or marine vehicles.

We’ve put together a helpful list of standard terms and definitions that you’ll come across when diving into a DIY repair for your vehicle. From basic definitions and acronym explanations — our informative guide will get you on the right path and keep you informed.

Quantum Fuel Systems specializes in producing high-quality fuel system components for nearly every EFI-equipped engine on the market. Our excellent direct replacement parts are designed in-house and will meet or exceed OEM quality. We offer replacement fuel pumps, kits, and components for nearly all makes and models backed by an industry-leading lifetime warranty. Visit our complete catalog to order now.

Fuel Pump Terminology Explained

Electronic Fuel Injection: Electronic Fuel Injection (EFI) is any fuel delivery system that is electronically controlled by an Engine Control Unit (ECU). The name describes its function quite accurately because EFI systems inject fuel directly into an internal combustion engine’s manifold or cylinder. EFI has become the dominant fuel delivery method due to its inherent performance, emissions, and efficiency advantages over antiquated carbureted systems. There are several forms of fuel injection, such as single-point fuel injection, multi-point fuel injection, sequential fuel injection, and direct injection. Yet, they all follow the same fuel injection principles.

Fuel Injector: A fuel injector is one of the most crucial components in your EFI system; its function is where we get the name. A fuel injector is an electronically controlled valve and, when activated by your vehicle’s Engine Control Unit (ECU), sprays a precise amount of atomized fuel into the engine’s combustion chamber to facilitate an optimal air-fuel mixture under all operating conditions. QFS is an authorized dealer of fuel injectors from industry leaders such as Bosch, Injector Dynamics, RC Engineering, and Siemens Deka. We offer direct OE replacement and high-performance solutions for automotive, Powersport, and marine applications.

ECU/ECM: The Engine Control Unit (ECU) or Engine Control Module (ECM) is your vehicle’s brain and controls one or several electrical systems. Part of its duties is managing the EFI system, performing essential tasks like how long to hold the injectors open during each cycle to create the proper air-fuel ratio for any situation. It achieves this by monitoring data from several sensors and adapting accordingly.    

OE Replacement: Original Equipment Replacement. All QFS products for powersports, from fuel pumps, O-rings, and more, match OE specifications and are guaranteed to be direct drop-in replacements. 

OEM: Original Equipment Manufacturer.

Fuel Rail: A fuel rail is a high-pressure fuel line that delivers fuel to the fuel injector.

Fuel Pump Assembly: The fuel pump assembly often houses critical components such as the fuel pump, pressure regulator, fuel sending unit, and strainers or filters. QFS offers entire replacement assemblies for many makes and models. 

Fuel Sending Unit: A fuel sending unit measures the amount of fuel available in your fuel tank and communicates that information to the fuel gauge. It does not send fuel as the name suggests and instead sends an electrical current from the fuel level sensor to the fuel gauge. If your vehicle cannot accurately register fuel levels, a fault with this component can be the cause.

Fuel Pump: Direct OE replacement fuel pumps are what Quantum Fuel Systems specializes in, supporting nearly every corner of the automotive, Powersports, and marine market. The fuel pump delivers high-pressure liquid fuel to a carburetor or EFI system within the engine. All QFS fuel pumps feature an industry-leading lifetime warranty and are designed to withstand a variety of ethanol-gasoline fuel blends. 

Intank Fuel Pump: “Intank” or “in-tank” refers to the physical location of the fuel pump. An intank fuel pump is located inside the fuel tank and explicitly designed for that purpose. Intank fuel pumps typically achieve longer operational lifespans than alternative designs since they are submerged in liquid fuel, helping cool and lubricate the pump.

External/Inline Fuel Pump: External/Inline fuel pumps are mounted on the exterior and underneath a fuel tank, as they use gravity to feed fuel into the pump. An external/inline fuel pump is often far easier to service and replace due to its mounting location. 

Small Parts: This is a term that comes up in conversation with gearheads, sales staff, and suppliers within the fuel-system industry. “Small parts” refers to any components that are not the actual fuel pump. This can include but is not limited to; O-rings, gaskets, strainers, filters, pressure regulators, and other parts associated with fuel pumps. QFS has all the small parts you need to get your vehicle running again. 

Filters: Filters do the critical job of extracting harmful particulates from fuel to protect sensitive EFI components. QFS filters screen microscopic contaminants that collect in a fuel tank and ensure that your vehicle’s EFI system is running at its best. A car, motorcycle, ATV, UTV/Side-by-Side, or boat may employ one or more filters at various stages of the fuel system. 

Strainers: Strainers perform the same function as filters and are typically the first line of defense against fuel system contaminants. Common contaminants such as sand, dirt, dust, and gasoline varnish are screened out by QFS strainers, which feature multi-layer strainer media to filter even the smallest particulates. In addition, QFS strainers boast an expanded surface area, offering improved filtration abilities and extending the life of your fuel system components.

Pressure Regulator: The pressure regulator helps maintain proper PSI within your EFI system, allowing your fuel injectors to function correctly and air-fuel calculations to be as accurate as possible. 

Dual Pump System: Any fuel system that relies on two fuel pumps is a Dual Pump System. In these systems, a low-pressure fuel pump transfers fuel from the fuel tank to the engine, then a high-pressure fuel pump takes over and delivers fuel to the EFI system. These systems are commonly used in marine applications where the fuel tank is not near the engine. 

E85 Fuel (Flex Fuel): E85 is an ethanol-gasoline blend of fuel that can contain anywhere from 51% to 83% ethanol, depending on the season and location. E85, or Flex Fuel, is explicitly formulated for Flexible Fuel Vehicles (FFVs), meaning that the internal combustion engine is designed to support high-volume ethanol fuel blends. While cheaper than gasoline, it has less energy density and often results in reduced fuel economy. This fuel cannot be used in motorcycles and Powersport vehicles.

Tank: The fuel tank. Every ICE-powered machine has one (or more).

Performance: Performance fuel system equipment means that you need components with superior flow rates than what OE equipment can provide. When building high-horsepower engines, this type of equipment is an absolute necessity to meet the increased performance demands.

Polytetrafluoroethylene (PTFE): Polytetrafluoroethylene (PTFE) is a durable synthetic fluoropolymer used in all QFS corrugated flex hose lines. This robust plastic is hydrophobic and resistant to the harsh chemicals in today’s fuels, including E85. The corrugated design also prevents kinking and improves fitment in all uses.

AN Fittings: AN is a U.S. military-derived specification standard dating back to World War II, developed as a common standard between the Army and Navy branches. QFS is an authorized dealer of high-quality AN fittings from Phenix Industries, providing customers with the finest aftermarket high-performance fuel and brake system plumbing components available.

PSI/kPa: Pounds per Square Inch/Kilopascal are two standard measurement units when describing fuel pressure regulator specifications. PSI is an Imperial measurement, and kPa is metric. Be sure to reference what measurement unit your model-specific service manual cites.

LPH/GPH: Liters Per Hour/Gallons Per Hour are two frequently cited units of measurement used to reference the amount of fuel a pump can supply over time. 

Pulse Width Modulation (PWM): Pulse Width Modulation allows an ECU to control EFI fuel pressure by rapidly turning a fuel pump on and off. If more pressure is needed, the length of time the fuel pump is activated extends. Conversely, if less fuel pressure is required, the time the fuel pump is turned on is reduced. This can happen in milliseconds and extends the useful life of a fuel pump by allowing it to work less, operate at a lower temperature, and introduce less heat to the stored fuel. All QFS fuel pumps are PWM-ready.

Done Studying? Reach Out To Our Helpful Staff

Quantum Fuel Systems is open Monday through Friday, 8:00 a.m. to 5:00 p.m. PT. Any of our trained and qualified staff members are available to assist customers over the phone. Be sure to reach out to our support staff with any technical questions, and we’ll get back to you as soon as possible.

How to Diagnose Dual Fuel Pump Problems on Outboard Engines

How to Diagnose Dual Fuel Pump Problems on Outboard Engines

Modern outboard motors are reliable pieces of equipment capable of propelling our vessels for hundreds of service hours. As robust as they are, fuel pump troubles can still occur.

Today’s intricate Electronic Fuel Injection (EFI) marine engines often add complexity with features like dual fuel pump systems, making pinpointing fuel-related problems difficult. We will discuss how to diagnose fuel pump problems on outboard motors, specifically those with dual fuel pump systems.

If your outboard motor is suffering from a loss in performance, unable to run reliably, or won’t start at all — you may be dealing with fuel pumps that have failed.

We strongly suggest referencing the model-specific service manual for your outboard motor to confirm all technical specifications when performing diagnostics. Those figures can change depending on the year, make, and model of your outboard motor. 

If you do not feel qualified performing the following diagnostic work, please consult an authorized and licensed service technician.

Quantum Fuel Systems is a leader in direct-OEM replacement fuel system components, providing high-quality repair parts for major marine brands, such as Evinrude Outboards, Honda, Mercury Marine, Suzuki, Volvo, Yamaha, and more. QFS offers complete replacement kits, parts, and specialty to tools to get you back out on the water.

An unmatched lifetime warranty backs QFS products, and all orders are processed on the same business day, with free 2-day shipping within the United States for any order above $60. 

What Is a Dual Fuel Pump System?

A dual fuel pump system relies on a low-pressure and a high-pressure fuel pump to perform separate tasks. A low-pressure fuel pump lifts fuel from your fuel tank to your outboard motor’s Vapor Separator Tank, also referred to as a Fuel Supply Module, depending on the manufacturer. 

VSTs/FSMs house all sensitive fuel-delivery-related components. Often, you may see the low-pressure pump described as a “lift pump” because of its primary function. It does not pressurize the EFI system or injectors in any capacity.

Once fuel is transferred into the VST/FSM, the high-pressure fuel pump can pressurize the high-pressure fuel rail and allow your EFI system to function as intended. 

It is essential to recognize that high and low-pressure fuel pumps have unique technical specifications because of their different purposes in the system. However, the same testing procedures apply to both fuel pumps, and it simply means you will repeat the processes for each pump. 

Typically, both fuel pumps in a dual-pump system will not fail simultaneously, meaning that owners can save money by knowing how and when to upgrade with high-quality QFS fuel pumps.

Symptoms of a Bad Outboard Motor Fuel Pump


Before diving into diagnosis methods, we will outline a few common symptoms related to bad fuel pumps. These are general symptoms and are often seen in various automotive, marine, or Powersports applications.

Failing to start or Maintain Idle

An engine that fails to start when electrical, starting, and filter systems appear to be in good condition usually indicates that fuel is not reaching the EFI system. In most cases, that means a fuel pump has ceased working entirely.

Similarly, an engine that starts but cannot maintain a steady idle is another sign that the pumping system has a fault. 

Losing Power When Throttling Up

Throttling up and raising engine rpm puts more stress on the fuel system, demanding greater fuel pressure and flow to meet performance requirements. While your outboard engine might behave normally at low rpm, it may stall, sputter, or lose power as the rpm climbs, signaling that the fuel pumps are operating inconsistently and unable to keep up. 

Increased Engine Temperature

Your outboard motor could appear to be working normally and propelling your vessel as it should, yet it seems to be running hotter than average. Often, this situation can signal that the optimal fuel/air mixture isn’t achieved, due to a restricted or underperforming pumping system.

Diagnosing a Bad Dual Fuel Pump System

Resolving fueling issues is done through the process of elimination and can be tricky since electrical and fuel systems are related. These tips should help you narrow down the possibilities and uncover the cause of your problems.

Most of the diagnostic suggested here will only require you to listen, observe, and use basic hand tools (screwdrivers, sockets, and pliers). Advanced diagnosis methods will require specialized tools such as a pressure testing gauge and a voltage meter or multimeter.

We also encourage wearing eye protection and nitrile gloves when dealing with fuel and fuel-related components.

Start With the Basics

  • Confirm there is fuel in the tank and that the fuel gauge is registering accurately.
  • Confirm that your electrical charging system is in good health; all connections are free of corrosion and buildup, all fuses are intact, and the electrical system is functional.
  • Confirm all fuel system components are in working order; check that filters, screens, fuel lines, connections, and seals are adequately maintained.

Listen for Fuel Pump Priming

In most cases, your fuel pump(s) will quit working unexpectedly. When faced with a situation where you go to fire your boat up, it cranks but won’t start; we’ll need to pause and listen if the fuel pumps are priming. 

Priming is when a fuel pump engages for a short period. Note that on a dual pump fuel system, both pumps will prime — the low-pressure pump draws fuel into the VST/FSM, and the high-pressure pump primes the EFI system.

Testing this is simple. Cycle the ignition to the “on” position and listen closely for an audible whine or whirring coming from the outboard motor. This whirring sound will last a few seconds. Repeat this process multiple times and confirm whether or not you hear a mechanical whine. 

If nothing is heard while cycling the ignition on, the fuel pumps may have failed, or the pumps may not be receiving electrical power.

Inspect the VST/FSM Assemblies

Most outboard motors use VST/FSM assemblies to house fuel-related components such as a limited amount of fuel, a float or float switch, various filters, and a pressure regulator. These designs and specifications will change with the make and model of your particular engine, so please reference your service manual for exact information.

The low-pressure fuel pump draws fuel from the tank into the VST/FSM. Gain access to the VST/FSM and inspect whether or not fuel is being deposited into the VST/FSM container.

Once again, always refer to your authorized service manual for proper removal procedures.

If no fuel is present in the VST/FSM, chances are the low-pressure fuel pump is malfunctioning and not delivering fuel. If an adequate amount of fuel is available, the problem could be with the high-pressure fuel pump.

Check for Electrical Power to Fuel Pumps

Generally, if your fuel pumps are not priming, you will want to confirm that they’re receiving electrical power. These tests will help determine if your issues are tied to the electrical system or the fuel pumps.

Using a multimeter or voltage meter, we can inspect the various electrical connections and determine if the required amount of electrical current is traveling down through the wiring harness to each fuel pump. Since we are dealing with dual pump systems, you’ll need to repeat the steps for both the high and low-pressure fuel pumps.

Consult your service manual and wiring diagram to determine which terminal connections to measure. Remove the relevant terminals from the pump and cycle the key to the “on” position while measuring the voltage.

The voltage should rise to the stated technical specification in your service manual and return to zero after several seconds. If no voltage or insufficient voltage is measured at these terminals, your problem is likely electrical.

If your wiring harness is delivering power, then it’s time to perform a continuity test on the fuel pumps themselves with your multimeter. A continuity test confirms if an electrical circuit can be completed and is impossible when a fuel pump’s electric motor burns out. 

Pressure Testing Fuel Pumps

Pressure testing is helpful if your outboard motor is experiencing sputtering or stalling since inconsistent pressure in your fuel system can create these problems. Luckily, most modern outboard motors feature threaded testing valves on the high and low-pressure sides of the fuel system.

A pressure gauge can be acquired from any authorized dealer or marine retailer. 

Refer to your service manual for fuel pressure specifications, install the pressure tester, and then cycle the ignition “on.” The pressure should rise and maintain at the cited specification.

Start the engine and increase the throttle slowly while noting if the fuel pump can maintain pressure within its recommended range. Repeat the process for both fuel pumps. 

If pressure is abnormally low or nonexistent, then you’ve most likely discovered your problem.

For reference, pressures higher than the recommended range indicate that the pressure regulator is defective. By the same logic, clogged fuel filters and leaking fuel lines can decrease pressure significantly.

Inspect all components thoroughly, and we offer complete replacement kits for all major brands, including fuel pumps, seals, and filters, to get the job done.

Order Now

Quantum Fuel Systems is open Monday through Friday, 8:00 a.m. to 5:00 p.m. PT. Place orders over the phone or browse our extensive catalog. For technical questions, visit our support page, and we’ll get back to you as soon as possible. 

  • Identifying problems with dual-pump setups. Many outboard systems consist of high & low pressure fuel pumps in a single system. Users can save money by identifying which pump is causing issues.

As far as the dual pump system goes, its crucial to test them out independently. For the high pressure pump, the standard procedure for testing the fuel pump (electric, pressure test, etc.) will suffice for determining if that fuel pump needs to be replaced. Pressure test the low pressure pump is more difficult due to its nature of it being a low pressure pump. They suggest the electric connection test as the most efficient way to test the low pressure pump.

Summary


  • Understanding the symptoms and how to diagnose a bad fuel pump on an ATV, motorcycle, or UTV/SxS is handy knowledge for any enthusiast
  • When a fuel pump fails to operate within its designed specifications, your EFI-powered vehicle can suffer in a few ways — robbing performance, causing it to run poorly, or failing to start at all
  • Pinning-down fuel issues can be complex, as fuel systems and electrical systems are interdependent
  • Priming means that the fuel pump engages for a short time, pressurizing the fuel lines and providing adequate fuel flow for the injectors
  • Pressure testing is crucial when faced with lean and rich conditions, power loss, or surging
Get Back on the road with confidence shop QFS

How to Tell When Your Motorcycle or Dirt Bike Fuel Filter Has Gone Bad

How to Tell When Your Motorcycle or Dirt Bike Fuel Filter Has Gone Bad

The riding season is getting into full swing, and that means many owners that have parked their motorcycles during the colder winter months are getting back out there. Before hitting the road, we always recommend a thorough inspection of your bike and ensure that you follow all of the recommended service intervals outlined in your vehicle’s manual. 

Checking or changing critical fluids, lubricants, tires, chains, sprockets, or belt drives are just a few of the crucial things on any conscientious rider’s maintenance checklist. Still, a commonly overlooked component is the fuel filter.

We’re going to outline the importance of your fuel filter and how to determine if yours has gone bad, robbing your precious motorcycle of its performance.

Whether you’re crossing the country on your American V-twin from Harley-Davidson and Indian Motorcycle, taking to the streets on your Aprilia, BMW, and Ducati, or hitting the trail aboard a Honda, Kawasaki, Suzuki, or Yamaha — every motorcycle equipped with Electronic Fuel Injection (EFI) uses a fuel filter.

Quantum Fuel Systems is a leader in high-quality fuel system components. We have top-notch direct replacement parts that meet and exceed OEM quality and are specifically designed to withstand harsh ethanol-based fuels.

QFS offers replacement fuel filters for nearly all makes and models, backed by an industry-leading lifetime warranty, which can be found by visiting our robust catalog.

Fuel filters come in a variety of shapes and sizes. Basic in-tank filters, in-line filters, and strainers are the more common types, and your vehicle may use one or more throughout its fueling system.

Yet, they all do the same job: Filter gasoline running through your EFI system, protecting components from debris, impurities, and contaminants that may work their way into your fuel tank. 

What Are The Symptoms of a Bad Fuel Filter?

A fuel filter past its prime will restrict or, in extreme cases, block fuel flow entirely. Clogged fuel filters usually create a handful of symptoms related to fuel starvation that result in decreased engine performance. 

These symptoms are pretty general when dealing with fuel system issues and can appear to be problems related to your fuel pump. For more information on fuel pump related questions, check out our article entitled: How to Diagnose a Bad ATV, Motorcycle, UTV/Side-by-Side Fuel Pump. 

Here are just a few symptoms related to a bad fuel filter:

Hard-Starting/Rough Idle

Hard-starting is when a vehicle takes more cranking than usual start. A rough idle is when your vehicle’s engine is not idling consistently and reliably, typically indicating some flow restriction in your vehicle’s fuel system. 

Stalling

Repeated stalling throughout the rev range is often a sign that your engine is starved of fuel. This could happen during idle, when beginning to accelerate, or decelerate. 

Throttle Hesitation / Performance Loss

Blockages in the filter may prevent an adequate amount of fuel from reaching the engine as the rider opens the throttle and the rpm climbs. 

What Causes A Fuel Filter To Fail?

A properly working fuel filter will protect sensitive EFI components, such as your fuel injectors and prevent them from becoming clogged or damaged by debris in your fuel tank. However, once a fuel filter becomes saturated with debris, it can restrict fuel flow.

Not only will that hinder engine performance, but fuel-flow restrictions overwork other components such as fuel pumps, causing unnecessary wear and premature failure. 

Your fuel filter will inevitably reach the end of its filtering potential with time and use since it is a consumable component. Much like swapping tires, changing oil, or servicing final-drive systems — inspecting and replacing fuel filters is part of routine maintenance. 

Over time, contaminants will inundate the filter and prevent it from performing its duties effectively. This is typically caused by sand, dirt, and various detritus mixing with gasoline varnish that collects in your fuel tank.

Gasoline varnish is a sticky caramel-colored substance left by fuel as it ages and deteriorates, binding particulates together and clogging filters.

Operating your vehicle and strictly using high-quality fuels will slow this process dramatically. However, some riders may only ride seasonally or even less, which makes storing your vehicle correctly even more important — draining unused fuel or adding a fuel stabilizer is recommended for extended storage situations.

While typically seen in older vehicles, ethanol-based fuels can be particularly harsh on inferior plastics and rubbers, causing them to break down entirely, leading to other mechanical problems. Rest assured, all QFS replacement fuel filters are designed to withstand modern fuels.

When Do You Change Fuel Filters?

Refer to your model-specific authorized owner’s manual for manufacturer suggested timelines regarding fuel filter replacement. In our experience, most manufacturers recommend replacing fuel filters every two years or every 20,000 miles for street-oriented motorcycles. 

Off-road motorcycles often require much shorter fuel filter service intervals because these vehicles operate in harsher climates, which are more likely to introduce dust, dirt, and other debris into the fuel tank. 

How Do You Diagnose A Bad Fuel Filter?

Fuel filters come in a variety of shapes, sizes, and types. When dealing with filters that can be inspected visually, such as our HFP-K42 (Replaces OEM 61011-04A) filter commonly seen in Harley-Davidson Dyna, Softail, and Touring models, use the original filter color as a reference point.

As you use your vehicle and cycle fuel through the fuel tank, these filters or strainers will become darker in color when oils, gasoline varnish, and other contaminants are absorbed. We recommend replacing these filters with reliable QFS products if they seem particularly discolored.

In other cases, you may not be able to visually inspect the filter because it is housed within a cartridge. When faced with this situation, disconnect the fuel filter from the system and attempt to pass air through the filter’s inlet.

Air should flow relatively freely through the filter. However, if it is clogged with pollutants, air flow will be obstructed, signaling that it is time to replace it. 

We strongly encourage our customers to thoroughly and adequately assess the condition of their fuel system and upgrade with direct OEM replacement components from QFS. Our complete fuel pump replacement kits are complete with a durable fuel pump and high-quality o-rings, seals, filters, and strainers for nearly all makes and models.

Have Any Questions? Reach Out To Our Qualified Staff!

Quantum Fuel Systems is open Monday through Friday, 8:00 a.m. to 5:00 p.m. PT. We are happy to assist our customers over the phone, or you can browse our extensive catalog. Reach out directly to our support staff for any specific technical questions, and we’ll get back to you as soon as possible.

Summary


  • A commonly overlooked component is the fuel filter
  • Symptoms are pretty general when dealing with fuel system issues and can appear to be problems related to your fuel pump
  • Most manufacturers recommend replacing fuel filters every two years or every 20,000 miles for street-oriented motorcycles
Get Back on the road with confidence shop QFS

How to Diagnose a Bad ATV, Motorcycle, UTV/Side-by-Side Fuel Pump

How to Diagnose a Bad ATV, Motorcycle, UTV/Side-by-Side Fuel Pump

A properly functioning fuel pump is one of the many crucial components in your ATV, motorcycle, or UTV/Side-by-Side (SxS). When a fuel pump fails to operate within its designed specifications, your EFI-powered vehicle can suffer in a few ways — robbing performance, causing it to run poorly, or failing to start at all.

Understanding the symptoms and how to diagnose a bad fuel pump on an ATV, motorcycle, or UTV/SxS is handy knowledge for any enthusiast and precisely what we’ll be discussing below.

Quantum Fuel Systems specializes in high-quality direct OEM replacement fuel system and engine management components backed by an industry-leading lifetime warranty. Every product in our extensive Powersports product line is designed to match the technical specifications of your vehicle.

We know how important it is for our customers to get back on the road or trail, that’s why your orders are processed the same business day, and we offer free 2-day shipping in the United States with any purchase above $60. QFS has you covered with complete replacement kits, individual parts, specialty tools, and more. 

Whether we’re talking about two or four-wheeled vehicles, testing a bad fuel pump, or issues related to your fuel system are similar. It doesn’t matter if you drive an Arctic Cat, Can-Am, or Polaris, ride a Harley-Davidson, Honda, or Husqvarna — fuel pumps can fail anytime, anywhere.

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What does matter is that you’re referencing your vehicle-specific service manual to confirm any necessary technical specifications, as those figures can change depending on the vehicle year, make, and model.

Luckily, troubleshooting a bad fuel pump follows the same general principles, and we’ll be covering a few basic and advanced methods.

QFS does not intend this article to be a strict guide. As always, we recommend that only those confident in their mechanical abilities perform maintenance, repairs, and diagnosis on their vehicles.

If you do not feel comfortable performing this work, please consult an authorized and licensed service technician.

Tools You’ll Need

  • Eye protection
  • Nitrile gloves
  • Hand tools (socket and screwdriver set)
  • Pliers
  • Multimeter or voltage meter
  • Pressure testing gauge
  • Contact cleaner
  • Rags

Symptoms of a Bad Fuel Pump

Let’s dive into it and review some tell-tale symptoms of an underperforming or failed fuel pump.

Not Starting/Won’t Idle

Not starting when all systems appeared to be in regular working order is a good indicator that fuel is not making it through the fuel system. If the engine does start but fails to maintain idle, that is another sign that the pump is on its way out. 

Whining

All fuel pumps produce a low audible hum when operating. When they reach the end of their lifespan, you may notice a loud whining sound, pointing to a fuel pump motor stressing itself to function.

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Surging

Surging occurs when traveling at a constant speed and feels as if your ATV, motorcycle or UTV briefly accelerates with no input from the user. Typically, excessive pressure buildup can momentarily deliver excess fuel. In this case, we strongly recommend replacing the pump and filters immediately.

Power Loss Under Load/Cut outs

Does your bike, quad, or SxS accelerate normally only to begin losing power as the rpm climb or at higher rpm? That is often a signal of a fuel pump that cannot deliver the correct amount of fuel pressure to meet performance demands. Alternatively, you may experience power cut-outs at random, demonstrating a fuel pump operating sporadically.

Diagnosing a Bad Fuel Pump

Pinning-down fuel issues can be complex, as fuel systems and electrical systems are interdependent. Problems with one system can cause the other to malfunction. Our goal here is to isolate variables and help you determine the root cause of your issues.

Before you turn a single wrench, start with the basics and confirm a few things:

  • Is there fuel in the tank, and does your fuel gauge (if applicable) register accurately? 
  • Is your battery adequately charged, and does your electrical system appear to be fully operational? 
  • Is the kill switch in the “run” position?
  • Is your bike, SxS, or quad in neutral?

If you’ve answered yes to all those questions and you’re still experiencing issues, then it’s time to start investigating.

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Fuel Pump Won’t Prime

Fuel pumps can fail with or without warning. We go to fire up our ATV, motorcycle, or UTV; the engine cranks, and it simply won’t start. Our first step is to observe if the fuel pump is operational and “priming.”

Priming means that the fuel pump engages for a short time, pressurizing the fuel lines and providing adequate fuel flow for the injectors. 

To test this, cycle your key to the “on” position and listen intently for an audible hum coming from the fuel tank. The hum should only last a few seconds.

If you’ve repeated this multiple times and don’t hear a mechanical whirring, chances are the fuel pump has failed or is not being supplied electricity.

If you are performing this test on a dirt bike (Motocross or Enduro) that doesn’t have a keyed ignition, press the starter button and quickly release, which will trigger the fuel pump and allow you to determine if the fuel pump is operational.

Check the Fuses & Relays

Fuses and relays act as bridges for electrical current. If they fail, the current can’t reach its proper destination and provide power. Consult your service manual to access your fuse box and relays, and then remove them to inspect them for any damage visually.

A healthy fuse will have its metal “bridge” connected, and a functional relay will “click” when power is delivered. You can also use a multimeter to check the resistance of a relay or fuse, which is more accurate.

Confirming Your Fuel Pump Has Power

If your fuel pump is not priming, you must determine if this is an electrical problem or a fuel pump failure. To do that, you will need to gain access to your vehicle’s fuel pump assembly. Consult your model-specific service manual for instructions to perform this safely. 

Once you have clear access to the fuel pump assembly, you will want to test if power is coming down to the fuel pump itself with a multimeter or voltage meter.

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Disconnect the wiring from the fuel pump assembly. Again, you will need to consult your service manual and wiring diagram to determine which terminal connections to measure.

Once you’ve done that, confirm that adequate power is available by cycling the key to the “on” position and measuring the voltage — it should rise to the cited technical specification in your service manual, then fall to zero after a few seconds. If you don’t have power or insufficient voltage, you know that the issue is not related to your fuel system.

If all is in order with the wiring harness, perform a continuity test with your multimeter on the fuel pump itself. Locate the positive and negative leads going to the fuel pump and check if an electrical connection is capable.

If it isn’t, rest assured that the fuel pump motor is dead. 

Pressure Testing a Fuel Pump

Pressure testing is crucial when faced with lean and rich conditions, power loss, or surging, as irregular pressure in your fuel system can cause these issues. This test requires one of the few specialized tools mentioned here since it will need a gauge with model-specific connections to be installed between the vehicle’s fuel pump and fuel lines.

Once you’ve determined your vehicle’s fuel pressure specifications and installed the pressure tester, cycle the key to the “on” position. Pressure must raise and hold at the required specification.

If that checks out, start the engine and increase the rpm gradually. Once again, pressure should not deviate outside the recommended range. 

If pressure is excessively high, your pressure regulator has failed, and we offer replacement options. Conversely, clogged fuel filters can lower fuel pressure and create flow issues.

Inspect all relevant filters thoroughly, although we recommend replacing them during this type of service.

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You can order from Quantum Fuel Systems, Monday through Friday, 8:00 a.m. to 5:00 p.m. PT, over the phone or browse our extensive catalog. Be sure to contact use our support page for any detailed technical questions, and we’ll get back to you as soon as possible.

Summary


  • Understanding the symptoms and how to diagnose a bad fuel pump on an ATV, motorcycle, or UTV/SxS is handy knowledge for any enthusiast
  • When a fuel pump fails to operate within its designed specifications, your EFI-powered vehicle can suffer in a few ways — robbing performance, causing it to run poorly, or failing to start at all
  • Pinning-down fuel issues can be complex, as fuel systems and electrical systems are interdependent
  • Priming means that the fuel pump engages for a short time, pressurizing the fuel lines and providing adequate fuel flow for the injectors
  • Pressure testing is crucial when faced with lean and rich conditions, power loss, or surging
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