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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.

Why Your Polaris Ranger, RZR, or Sportsman OEM Fuel Pump Fails Prematurely

Why Your Polaris Ranger, RZR, or Sportsman OEM Fuel Pump Fails Prematurely

Polaris is a household name in the Powersports industry with its complete range of snowmobile, ATV, and side-by-side/UTV products. Whether you’re an off-road enthusiast using your sport SxS or ATV for recreation or utilizing one of the brand’s many UTV models on the job, the Polaris lineup is incredibly robust and offers something for nearly everyone. 

As much as Quantum Fuel Systems customers and staff enjoy Polaris vehicles, we’ve noticed that several Polaris Ranger, RZR, and Sportsman models use an OEM fuel pump prone to premature failure. We’re going to explain some of the causes and outline helpful solutions.

Impacted Polaris ATVs and UTVs

  • 2011-2012 Ranger 800 
  • 2013-2017 Ranger 800 
  • 2013-2019 Ranger 900
  • 2014-2022 Ranger 570
  • 2012-2016 RZR 570
  • 2011-2014 RZR 800
  • 2014 RZR 900
  • 2011-2013 RZR XP 900
  • 2011-2014 Sportsman 550
  • 2011-2014 Sportsman 850

Fuel pump problems on these common Polaris models can happen at any time. Polaris riders and drivers often have difficulty restarting their machines in hot climates, forcing them to let the vehicle cool off for roughly 30 minutes and hoping it will fire up again.

The original Bosch manufactured stock fuel pump is prone to these symptoms in particular models. Riders need a dependable fuel pump that excels in these rugged conditions.

Quantum Fuel Systems offers cost-effective fuel pump and fuel management components that are built to meet and exceed OEM performance. All QFS replacement components are designed to match dimensional and functional specifications.

You won’t need to modify your original assembly — our drop-in replacement parts will work for your specific application and feature an industry-leading lifetime warranty. If you need Polaris replacement components, refer to our catalog to find an exact match for your year, make, and model.

Over the years, our expert team of QFS technicians has pinpointed the cause of these issues. Whether it’s a total fuel pump failure or an intermittent problem, properly identifying the cause of these problems can save you a headache down the road.

O-Ring Wear Leads to Fuel Pump Failure

O-rings are the unsung heroes of our fuel system, creating effective seals and ensuring that our entire fuel system can maintain proper pressure. Unfortunately, the OEM fuel pump o-ring is constructed out of an inferior rubber and is prone to early deterioration, deformation, or cracking.

We find that this o-ring is often the leading cause of fuel pump failures with Polaris vehicles.

Once that seal begins to fail, fuel pressure can bleed back into the tank, creating engine performance issues, hard starting conditions, or failing to start at all. However, the more detrimental problem with a fuel system that fails to maintain proper pressure is that is overworks the fuel pump, generating excess heat and eventually leading to premature fuel pump failure.

Often, this total failure occurs without warning and can leave you stranded. 

QFS fuel pump installation kits come with every replacement component you’ll need to get up and running again, including our extremely durable Viton ethanol-safe fuel pump o-rings. One of the most common fuel pump o-rings for Polaris models is HFP-OR-396.

Please take extra care when installing new o-rings, properly lubricating the o-ring and assembly cavity. This procedure will prevent the o-ring from becoming pinched or torn and create an effective seal. 

We strongly suggest completely servicing your entire fuel system while installing this upgraded o-ring. Check that your filters are clear and gaskets are in proper working order.

Vapor Lock

Vapor lock was a common problem on engines that utilized carburetors, and it has become less of an issue with the advent of Electronic Fuel Injection (EFI). While somewhat rare with modern EFI vehicles, it can still happen, specifically when operating in extreme temperatures. 

Vapor lock occurs when fuel begins to vaporize in the fuel system, elevating the pressure within the fuel system and creating difficulties for pumps designed to transport liquid fuel, not vapor. Fuel pumps attempting to operate in a system with vapor lock are subject to excessive wear and lead to early failure.

Symptoms riders and drives might observe include: Hard starting, stalling, or sputtering when running their machines in hot conditions.

A reoccurring vapor locking issue was documented on 2011-2012 Polaris Ranger 800 UTV models due to an underrated 40 psi (300kPa) pressure regulator. 2013 Polaris Ranger 800 models solved this issue with an upgraded 58 psi (400kPa) pressure regulator to overcome hot fuel tank issues that raised internal pressure.

In the case of the 2011-2017 Ranger 800 UTVs, our HFP-396 fuel pump is the correct replacement, but kits for specific years will differ in their choice of the pressure regulator.

There are a handful of solutions for the 2011-2012 Ranger 800. Unfortunately, you will need to work with your authorized Polaris dealer or a trusted performance mechanic as you will need to reflash the ECU to remedy vapor lock problems completely. 

The first solution assumes that you will retain the 40 psi (300kPa) pressure regulator. This is typically used when owners experience difficulty restarting their Ranger 800 when hot. If that is the case, you will need to reflash your Ranger 800 with a map that holds the fuel injectors open longer, prior to a hot start, in order to bleed excess fuel vapor from the system. 

2011-2012 Ranger 800 owners can choose to upgrade to a 58 psi (400kPa) regulator. This option is effective for owners that experience random stalling, or shut offs while coming to a stop. Once again, this will require an ECU reflash to compensate for higher psi limits.

Ultimately, vapor locking seen on 2011-2012 Polaris Ranger 800 models can only be remedied with a modified fuel map. However, it highlights the importance of using fuel system components built to withstand high temperatures and extreme environments.

Have More Questions? Reach Out to Our QFS Staff!

Quantum Fuel Systems is open Monday through Friday, 8:00 a.m. to 5:00 p.m. PT. You can speak to any of our qualified staff on the phone or browse our extensive catalog. Be sure to contact use our support page for any detailed technical questions.

SUMMARY

  • Some OEM fuel pump prone to premature failure
  • Reference the above list of years / models to determine if your vehicle is prone to premature failure
  • You won’t need to modify your original assembly — QFS drop-in replacement parts will work for your specific application
  • O-rings create effective seals and ensure fuel systems can maintain proper pressure
  • While somewhat rare with modern EFI vehicles vapor lock can still happen, specifically when operating in extreme temperatures

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.

We Are Standing By For Your Order

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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