Fuel System Basics - Tips And Tricks For The Entry-Level Racer - Circle Track Magazine (2022)

The weekly racer faces some very real challenges with fuel systems. These problems are manifest in trying to make a fuel system that was designed for passenger cars feed an engine living in a racing environment. Even slight modifications, such as improved airflow through the use of a larger carburetor, the addition of improved exhaust, and ignition systems will enable an engine that has very limited internal modifications to develop more power, have an expanded rpm range and, subsequently, a greater need for fuel to supply these even limited modifications.

Engines for the weekly racer can range from a bone stock motor complete with air cleaner and mufflers to a highly tuned 500- to 600hp engine with very specialized fuel system needs. The weekly racer also has to deal with a variety of fuels, ranging from pump gasoline, E85, or race gas and, at the outer limits of the fuel spectrum, alcohol. All of these factors dictate the complexity of the fuel system. The amount of load that system will have to bear varies greatly.

For the most part, the weekly racer running at the local bullring will have a fuel system that is just a warmed over OEM system. Many of these race cars began life as daily drivers, never designed to be consistently driven at or near maximum power levels. Since the needs of the racer are so much different, stock fuel systems must be modified and improved to sustain the power requirements.

A typical short track fuel system is fairly simple. It includes a fuel tank or possibly a fuel cell, fuel lines, a fuel filter or two, and a fuel pump. If electronic fuel injection is being used, the system will also include fuel injectors and a computer. If the fuel system is supplying a high-power engine, the use of a fuel pressure regulator is almost a certainty, which may include a return line to the fuel tank. In those cases, you have fuel traveling from the tank to the engine and a line to route fuel that is bypassed from the regulator back to the tank. It boils down to a simple equation: The more power the engine produces the more complex the fuel system.

Buying Fuel
Regardless of the system's complexity, it all begins with the point where you, the racer, buy your race fuel. This is a critical point in the fuel system that's often never given a second consideration, but it's just as important as any part of the fuel system on the car. It's at this point that racers begin to really control the fuel system, and we all know that racing is all about control.

The simple action of transferring the fuel from the point of sale to the race car can and does contribute to variation in the fuel system. The fuel may only be exposed to one or possibly two containers between the point of sale and the race car. Devices such as funnels and fill lines that may be dirty or have been exposed to water, or through the mixing of old fuel and new fuel will contaminate fresh fuel.

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The key is to treat your race fuel like you would treat the fuel that you put in your body. Keep it clean; make sure the containers you transfer fuel in are clean on the inside and the outside. Keep the fuel from becoming exposed to light and keep it cool.

Aside from the hopefully obvious safety aspects, poor fuel transportation and storage techniques can effectively take away some of the power producing components of the fuel. And I can think of very few racers who feel that they have too much power.

For example, everybody enjoys a sunny day but your race fuel likes dark and cool places and you should remember that. Fuel, especially gasoline, should always be stored in containers that do not allow the sunlight to reach the fuel. Most fuels are light sensitive and exposure to sunlight can and will damage the fuel. Prolonged exposure to sunlight can cause some race fuel to break down and some of the components to separate and once this happens it can't be undone. You can't just shake the container to mix the fuel components back together.

The containers should be either metal or an opaque plastic. If you're using plastic fuel cans and you are transferring gasoline, the best color is black. Translucent white fuel containers may look cool and may be the rage, but they aren't the best selection for the transportation and storage of fuel. You may be paying a price in diminished performance of the fuel for that cool look in the pits.

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The translucent, white, or light-colored containers are fine for alcohol-based fuels. But remember that alcohol has its own set of idiosyncrasies. Alcohol is hydroscopic; it will absorb water from exposure to the air. Leave alcohol in a vented container in even a dry climate and it will absorb water and the water will degrade the power producing aspects of the fuel. All fuels should be shielded from the sunlight not just due to damage caused by ultraviolet light but the elevated temperatures that are caused by turning your fuel cans into solar heaters. Fuel containers stored in direct sunlight and even indirect sunlight will hiss as they are opened. This hissing is all of that high-dollar fuel venting its lighter elements into the atmosphere.

Try to avoid storing fuel in your trailer as this can be a real safety hazard. If you can smell high concentrations of fuel vapor in the trailer when you open the door you have two problems. The first problem is that the fuel jugs should not be venting into the atmosphere at all, fix that problem by purchasing fuel containers with closable vents. The second problem is that your trailer should be vented better so that fumes of any sort that do escape can't gather in the trailer. The addition of some roof vents will help.

You need to remember that your fuel containers are really consumable items just like tires. They do not last forever and still wear out. If you're using plastic fuel containers, inspect them regularly for cracks around the container and cap/vents. When you find a crack, replace the container. And even if you don't and the container is several years old you should still replace it. If you are using metal containers you need to be on the lookout for rust in the can and around the fill points. Attention to small details is what separates the winners from the field fillers.

The majority of racers are unaware that many states have some very specific laws that govern the amount of fuel that can be carried in a vehicle outside of the tank. If you are going to transport fuel on the open road you need to be aware of the laws regarding the transporting of fuel.

Once the fuel reaches the tank we still need to be very conscious about keeping the fuel clean. Fuel cells don't last forever, the foam that's inside the bladder can break down over the course of a season or sooner depending on the fuel you are running. Some race fuels are very unkind to synthetic rubber products over time. If this happens the fuel will be contaminated by the foam and can cause some real fuel system problems. The foam should be replaced at the intervals sug-gested by the fuel cell manufacturer.

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If you are still using the OEM tank you are not home free just yet. It's entirely possible that the tank has seen a good number of over the road miles and is possibly or more than likely contaminated with rust and scale after many years of use as a grocery getter. You may want to remove the tank and have it cleaned. The truth of the matter is that once the OEM tank is removed you might as well think about installing a fuel cell just for the safety that this type of tank offers.

Getting the fuel from the cell or tank is accomplished with the fuel lines. If you're utilizing the OEM fuel lines, they're usually made up of a combination of hard lines made of steel or flexible steel lines and rubber or neoprene hoses. Steel lines are usually very durable. The caution point, if you're racing in a Street Stock-type of class, the OEM fuel lines, while very durable, are not designed for race cars. The elevated level of maintenance racers perform may cause wear and tear on the various components of the fuel lines, especially the fittings and threaded joints. You need to make sure that the fuel lines are routed in such a way that they are securely mounted to the chassis and are protected from any debris or errant broken part you may encounter on the track. If you have rerouted the fuel lines you need to make sure that the fuel line will not be in the way of any suspension parts that at their full range of movement could impact or rub on the fuel line. If you're running the fuel lines through the passenger compartment, most racing organizations require that the line be run through a section of steel tubing that will isolate the fuel line from leaking into the driver's compartment.

In order to get the fuel through the lines, most circle track race cars utilize an engine-mounted pump of some type. It may be located on the engine in the OEM position or it could be a beltdriven pump on the front of the engine or even an engine-mounted pump driven off the camshaft. It may take the form of a diaphragm, piston, or a gear-type pump. The amount of power the engine generates will dictate the type of pump utilized.

It's a fairly simple equation: The more power that the engine generates, the higher the need for a higher volume of fuel required. These types of high-volume pumps are usually found on engines running alcohol or very high horsepower gasoline engines. Some racers have opted to remove the mechanical fuel pumps and use electric pumps.

However, not all sanctioning bodies allow electric pumps. Due to the potential of the car being involved in a crash, the potential for fire is increased if a fuel line is damaged and the pump continues to run. While a very specific set of circumstances have to occur for this to play out, the risk is there and some racing organizations aren't willing to take that risk. Even so, there are many race cars racing safely that are using electric fuel pumps.

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You naturally need a filter for all this fuel traveling to the motor, but do we want the filter between the pump and the tank or between the pump and the carburetor? Filters placed between the pump and the tank, allow the use of larger filters in line. Mounting them to the chassis where they're out of the way makes them potentially more difficult to service. Or we can place the filter between the pump and the carburetor. This option has some advantages, such as making it easier to work on and if it's easier to work on, odds are that it will get serviced more often. Is there any one method that's better between the two options? Can't say for sure, but if you have a limit to the amount of fuel you can carry, placing the filter(s) between the tank and the pump allows you to use a larger filter to gain some fuel capacity.

However, nothing says you can't do both. Place filters between the tank and the pump that have a larger media that may not be as restrictive and use a filter between the pump and the carburetor that has a much finer media that captures smaller particles that may be in your fuel. Another advantage of placing a filter in front of the pump is that it keeps debris from possibly damaging the pump, especially if you're using a positive displacement mechanical pump that uses gears as opposed to a diaphragm-type of pump. If you have a high-dollar fuel pump, you will want to prevent any sort of debris from making it from the tank to the pump, possibly damaging the pump.

The next thing we need to consider is the pressure of the fuel at the carburetor. With an engine that is closer to the power levels of the OEM engine, fuel pressure is less of a concern than with a highly tuned engine. Along with a pressure regulator you'll also need a fuel-pressure gauge. Using a fuel-pressure gauge will allow you to measure the fuel pressure. The regulator needs to be mounted between the pump and the carburetor and depending on the type of regulator you may need to run a return line to the tank. The pressure gauge is one tool that you can't do without if you're running a fuel pressure regulator. With the gauge you'll always know the exact pressure you're getting at the carb. Remember, delivering too much fuel can cause just as many problems as not enough fuel. Being able to measure your fuel pressure gives you one more parameter to help you tune the car.

The gauge should be able to be read from inside the car while it's at speed. With that said, in the interest of safety, try to utilize a fuel-pressure gauge that utilizes an electronic sending unit so you don't have to run a fuel line into the driver's compartment.

There are no magical or mystical things about fuel systems. The components are easy to understand and the execution of constructing a good fuel system is something that is easily accomplished. A well-engineered fuel system is just that, a system for delivering winning performance and dependable operation in all racing situations.

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Do racing fuel cells expire? ›

How long does a fuel cell bladder last? Most ATL racing cells are warranteed for 5 years, which is the legal life span established by most racing organizations.

How do you troubleshoot a fuel system? ›

A fuel system should be carefully tested for pressure, volume, and electrical integrity before condemning the fuel pump. Often the first step in diagnosing a faulty fuel system is to simply listen. Turn the ignition key to the run position and carefully listen for a slight humming sound coming from the fuel tank.

How does Returnless fuel system work? ›

On returnless systems, fuel is picked up via the fuel screen sock at the bottom of the tank, then routed to the fuel pump. The pump supplies the needed fuel pressure and volume to the engine and the excess is directed back into the tank after passing through a pressure regulator.

Where does the fuel regulator go on a race car? ›

In many cases, you can mount the regulator in a location to satisfy ease of installation, adjustment, and appearance. However, in the cases of high power applications, extra low fuel pressure systems, and high-g launches, it's best to mount the regulator as close to the fuel delivery destination as possible.

Do you need foam in fuel cell? ›

Without the foam, there's a greater chance for fuel to spill over a wider area. The rubber fuel cell bladder itself is a part that must be inspected, especially after an accident. During the off-season, you need to pull the bladder from its casing and inspect it closely.

How long can you store racing fuel? ›

HOW LONG WILL THIS FUEL LAST IN STORAGE? VP Small Engine Fuel will remain stable more than two years when kept in its original sealed container. Even after pulling some of the fuel out, you're looking at about a two-year life as long as you properly re-seal your container.

What are some common fuel system problems? ›

Four Common Fuel System Problems and Their Causes
  • Bad or Clogged Fuel Injectors.
  • Clogged Fuel Filter.
  • Clogged or Leaking Fuel Lines.
  • Malfunctioning Fuel Pump.
  • Bonus: The Wrong Gasoline.
15 Dec 2020

Can ignition switch cause no power to fuel pump? ›

If the ignition relay shorts, burns out, or otherwise fails while the engine is operating it will cut off power to the fuel pump and ignition system. This will cause the vehicle to immediately stall due to fuel and spark being cut off.

What Is a Dead Head fuel system? ›

The term "dead head" simply means that the fuel in the system does not recirculate back to the gas tank from the front of the car. A return system recycles fuel back to the tank using either a bypass at the fuel pump or at the regulator.

What is a PWM fuel system? ›

The way the OEM's control the speed of the pump is by using Pulse Width Modulation (PWM). PWM is like turning a switch on and off very quickly. For example, if a switch is turned on for 10ms, then off for 10ms, and the cycle repeated, the pump is working at a 50% duty cycle.

What is a bypass fuel regulator? ›

A bypass regulator creates pressure by restricting flow from the pump, forcing the pump to produce pressure up to the regulator's set point. Once enough pressure is created the regulator bypass is forced open, allowing excess flow onto the return line.

What is the correct fuel pressure? ›

It is between 35 and 65 pounds per square inch (psi) on most vehicles.

Who makes the best fuel pressure regulator? ›

Best Fuel Pressure Regulator Reviews
  • Aeromotive 13129 Regulator. ...
  • WATERWICH Aluminum EFI Fuel Pressure Regulator Kit. ...
  • AEM 25-300BK Adjustable Fuel Pressure Regulator. ...
  • PTNHZ RACING Manual Adjustable Fuel Pressure Regulator. ...
  • PQY Fuel Pressure Regulator. ...
  • RJSPHH Fuel Pressure Regulator Kit. ...
  • Yokolas PSI Fuel Pressure Regulator Kit.
28 Jul 2022

Does fuel pressure regulator go before fuel rail? ›

The optimum EFI regulator location is after the fuel rail(s) when possible. All pump flow, minus engine consumption, must always run to the regulator, wherever it is. Putting it after the fuel rail means all fuel must run through the fuel rail, and over the injector inlet, at all times.

How much foam do you put in a fuel cell? ›

The foam will take up anywhere from 1% to 4% of the volume of the fuel cell. This varies depending on the gallon capacity of the fuel cell. The smaller fuel cells, like 1 to 5 gallons will be around 1% to 2%. The larger fuel cells, like 16 to 32 gallons will be around 3% to 4%.

Why is there a sponge in my gas tank? ›

What does a fuel tank sponge do? While displacing a very small amount of fuel, the Foam prevents sloshing of the fuel. By preventing sloshing the Foam keeps the fuel de-aerated which improves fuel delivery and also insures constant delivery of fuel to the pickup.

How do you cut fuel cell foam? ›

How to Cut Fuel Foam - The Easy Way! - YouTube

Can you mix racing fuel with regular gas? ›

We often get these two questions:

The answer to #1 is easy. Yes, you can mix any of our race fuels. But remember – if your engine needs an unleaded fuel, you don't want to mix leaded with unleaded. Doing so would make a leaded fuel which could still damage oxygen sensors and catalytic converters.

Does oxygenated fuel make more power? ›

The additional fuel that can be brought in with an oxygenated blend helps the engine create more power, but it requires more fuel to be delivered to the engine to prevent damage. Oxygenated fuels do help create more horsepower overall, but that usually isn't seen at the peak of the power curve.

Does race fuel burn hotter? ›

Using racing fuel in a street vehicle may result in a loss of efficiency because of the need for a hotter spark. Racing fuel may also cause damage to the catalytic converter and oxygen sensors installed on street vehicles.

What are the types of fuel system? ›

What are the basic types of fuel injection systems? The basic types of fuel injection systems are single-point fuel injection, multi-point fuel injection, sequential fuel injection, and direct injection.

What is the difference between a fuel pump and fuel injector? ›

The main difference between these two components is that the fuel injector atomizes the pressurized fuel and injects it into the combustion chamber while fuel pumps pressurize fuel and then send it to the fuel line and fuel injectors.

What causes fuel system failure? ›

Fuel pump failures can be caused by electrical faults, old age (wear) or fuel contaminants (dirt, moisture or bad gas). Fuel pump failures often occur without warning. Fuel pumps, injectors and pressure regulators are the three most commonly replaced fuel system components.

What happens when you have too much fuel pressure? ›

If fuel pressure is too high, your vehicle's engine could be over fueled, leading to many of the symptoms listed below. Some of these symptoms include your engine running rough, poor fuel economy and black smoke from the exhaust.

What happens if fuel pressure regulator is stuck open? ›

Q: What happens if a fuel pressure regulator is stuck open? If a fuel pressure regulator is stuck open, it will build up more pressure than it should. This will cause the fuel injectors to inject more gas into the cylinders, resulting in a rich air/fuel mixture.

How long should a fuel system hold pressure? ›

The basic leak-down test

For the specification we must consult service-data, but the system should hold some pressure for about five-minutes.

What sensor controls the fuel pump? ›

The fuel tank pressure sensor is part of the fuel pump assembly and is mounted on top of the tank or inside the tank. It's part of the evaporative emissions system (commonly referred to as “EVAP”) and reads pressure in the fuel system to detect evaporative leaks, such as a loose or faulty gas cap.

Is there a fuse for ignition switch? ›

The ignition relay is often located in the fuse box under the hood. It can also be located in a fuse box under the dashboard inside of the car. The ignition relay's exact location may differ from vehicle to vehicle depending on the design of the vehicle and the company that manufactured it.

Is there a fuse for a fuel pump? ›

In most car models, the fuel pump relay is located in a fuse box somewhere under your dashboard, but it can also be located in the fuse box in the engine bay. The engine's or the dashboard fuse box is usually a long black box containing a fuel pump relay and various other fuses and relays.

How much fuel should a fuel pump pump in 30 seconds? ›


For most applications, the fuel pump should produce at least three pints of fuel in 30 seconds.

Can you run a fuel regulator without a return line? ›

Advantages. Requires no fuel return line and fittings from the regulator to the fuel tank. This reduces weight, complexity (routing a return line can prove to be difficult), and expense.

Does a fuel regulator need a return line? ›

An adjustable fuel pressure regulator with return is required.

How does a pulse fuel pump work? ›

A pulse fuel pump uses the pressure differential produced by the engine to move a diaphragm inside the pump body. This pressure differential is generally transferred via a pulse tube to one side of a flexible diaphragm in the fuel pump.

How do you remove a fuel rail? ›

Remove Stuck Injectors & Fuel Rails - Easy How To DIY TIP - YouTube

How much pressure should be in a fuel rail? ›

Required fuel pressure can vary depending on your vehicle's engine and fuel system. Carbureted engines may require as little as 28 kPa (4 PSI), while modern multipoint fuel injected high-performance engines can require as much as 414 kPa (60 PSI).

How do you adjust a fuel pressure regulator? ›

Adjusting A Fuel Pressure Regulator "How To" ⛽️ - YouTube

What is code P0089? ›

What the P0089 code means. The P0089 is a diagnostic trouble code (DTC) for a fault found with the fuel pressure regulator. The fuel pressure regulator regulates how much fuel is delivered to the fuel injectors. The ECU controls the fuel pressure regulator and when a fault is detected the P0089 code is set.

How long does VP fuel last? ›

According to VP fuels website: “The length of time the fuel will stay fresh in a sealed drum depends on the fuel itself. A non-oxygenated fuel such as C12 should be used within a couple years. I personally have tested some that was eight years old and was fine.

What is in nitromethane fuel? ›

At its base level, nitromethane is an organic compound designated by the chemical formula CH3NO2 and is composed of carbon, hydrogen, nitrogen, and oxygen. It is used as an ingredient in explosives, pesticides, coatings, and—as you know—a fuel additive, particularly for motorsports vehicles.

Can you mix racing fuel with regular gas? ›

We often get these two questions:

The answer to #1 is easy. Yes, you can mix any of our race fuels. But remember – if your engine needs an unleaded fuel, you don't want to mix leaded with unleaded. Doing so would make a leaded fuel which could still damage oxygen sensors and catalytic converters.

Can you have too much octane? ›

Too Much Octane

Having a fuel with too high of an octane will not cause your engine to lose power. The problem is that the popular components used to make the octane of a fuel higher slows the burn rate and a fuel with a burn rate that is too slow can result in an engine power loss.

Does race fuel burn hotter? ›

Using racing fuel in a street vehicle may result in a loss of efficiency because of the need for a hotter spark. Racing fuel may also cause damage to the catalytic converter and oxygen sensors installed on street vehicles.

What happens if you put nitromethane in a regular car? ›

Trying to put regular racing gasoline, pure methanol, nitromethane, or leading racing fuel will completely ruin your engine. The same goes for a car tuned to use 87 octane gasoline. You cannot put anything other than gasoline in that car, or you risk causing costly damage to your engine.

How much money is a gallon of nitromethane? ›

There's nothing funny about paying $45 a gallon for nitromethane for a funny car—and burning 14 gallons on every single run. NHRA teams pay $1800 for a 40-gallon drum of nitromethane, so they're paying $45 a gallon—and that's a group discount negotiated for the entire racing season.

What octane is jet fuel? ›

The octane ratings of AVGAS, a gasoline-based fuel, are usually either 91 or 100 (lean mixture) and 96 or 130 (rich mixture). The octane rating of jet fuel is much lower, around 15 – this is much more like automotive diesel and thus much more resistant to detonating due to sparks or compression.


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