How to choose the right fuel pressure regulator

How to choose the right fuel pressure regulator.

With so many regulator options on the market how do you know which one is the right fuel pressure regulator for your install?

Deadhead regulator, bypass regulator, return or return-less, efi or carb. A ton of questions come up when thinking about pressure regulation and what is the best option for your fuel system install on your car or truck. This article will take you through some of the most common considerations when selecting a fuel pressure regulator as well as make some suggestions on products that we have found work well for our customers. 

How does a fuel pressure regulator function?

How do Return style or bypass regulators work? 

A return style regulator or bypass does exactly what the name implies, it bleeds off excess pressure in a return line back to the fuel tank. As the regulator sends excess pressure back to the tank you can expect a reliable operating pressure supplied to the fuel rail or carb. 

This pressure is controlled with a bypass valve that is spring actuated. As fuel flows through the regulator pressure increases in the system which forces the spring to open the bypass valve and allow the excess pressure to bleed off. Many aftermarket bypass regulators are adjustable, this means that you can adjust the seat pressure provided by the spring and adjust the pressure that the system will see at the carb or fuel rail.

Return style or bypass regulators are recommended for most EFI installations as well as carb installations when a high pressure pump is used. 

Advantages of a return style bypass fuel pressure regulator. 

- Fuel is always flowing through the system helping to keep the fuel temperature within operating conditions. 

- Allows high pressure pumps to operate at maximum efficiency

- Generally required for many installations

Disadvantages of return style bypass regulator. 

- Return line is a requirement increasing system complexity

How do Deadhead regulators work?

A deadhead regulator controls pressure in a much different way than a return style or bypass regulator. There is  no return line and as such when the pressure increases beyond what has been set the spring will close a valve to restrict fuel flow and in turn the pressure the system sees after the regulator decreases to the set amount. 

Advantages of deadhead style fuel pressure regulators.

- Simple one line installation

- Can be used in systems with a single pump but multiple regulators. 

Disadvantages of deadhead style regulators.

- Can not be used for most EFI systems

- Allows for an increase in fuel temperature

- Can be hard on the fuel pump as increased pressure is needed to close the valve.

- EFI pumps with this style of carb regulator can not be used.  

Do I even need a fuel pressure regulator?

There are a few considerations here if you need a fuel pressure regulator in your system at all. These relate mostly to the fuel pump you will be using for your application. Certain fuel pumps on carb systems are self regulating, this means that they will put out the pressure needed for the carb system usually 4-6 PSI.  

PWM or pulse width modulation fuel pressure control that some factory EFI systems use do not need to be externally regulated. 

Return Style LS engines already have a fuel pressure regulator built into the fuel rail so an external regulator is not needed. 

What type of fuel system do I have?

The first step in making a fuel pressure regulator decision is to identify what type of install you are planning. As stated earlier if you have a system that already has a regulator or if you have a self regulating pump there is no need to make any further decisions. Read on to learn about what is required for other fueling applications. 

Carbureted systems

Low pressure mechanical pump - Usually no fuel pressure regulator needed.

High pressure mechanical, high flow mechanical, and belt driven pumps - A regulator will be required, most likely a return style regulator but this will be determined by each pumps manufacturer. Higher horsepower applications will most likely need a return style regulator. 

Low pressure electric pump - These pumps can come in multiple flavors, some will be self regulating and will not require a regulator. They are often sold with a predetermined pressure range so be sure to select the correct one for the operating pressure needed by your carb. If the low pressure electric fuel pump operates above what your carb requires then a deadhead style regulator is usually warranted for this application. 

High pressure EFI electric fuel pump - A return style regulator designed for carburetors is required. We recommend the Holley 12-840 for this application. Found HERE. This regulator is adjustable between 4.5 and 9lbs of pressure. 

If you are planning to move to an EFI system at a later date some regulators can be converted between being an EFI style and a Carb style fuel pressure regulator such as the Aeromotive 13301 found HERE. 

EFI systems (non direct injection)

There is less combinations available for EFI systems as you must run a high pressure fuel pump that meets the needs of the system and power targets. Running a low pressure pump is not an option and as such you must regulate the pressure in these installs. 

LS swaps with a return-less intake. A factory style corvette regulator is perfect for these installs up to a fuel pump flow rate of 255LPh. The regulators can be found HERE with AN fittings or we also carry a complete LS swap kit that includes the corvette style filter/regulator unit found HERE. The nice thing about these units is they double as a fuel filter reducing overall system cost. 

LS swaps with a higher flow fuel pump and other EFI systems that require a different pressure than 58 PSI. An adjustable fuel pressure regulator with return is required. We recommend the Aeromotive 13129 found HERE. This regulator features a gauge port built in and will support builds up to 1000HP. 6 ORB ports for feed and return allows you to adapt it to many different fuel systems. This regulator is also boost referenced if you require that feature. 

Fuel systems with extremely high flow rate pumps and high power levels over 1000HP. With these installations we recommend that you reach out to us to discuss all the variables in your install our customers have had great luck with the Aeromotive X1 pro regulator found HERE. 

EFI systems with Direct Injection. These systems require a higher initial operating pressure and from OEM are usually controlled using a PWM system for regulation. With GM gen V motors for example while they will operate with as low as 58PSI you may have struggles getting the engine to operate correctly. We recommend setting the regulator at 72PSI if you insist on running the non PWM system. Of course the best course of action would be to do what the GM engineers intended and setup the PWM system for the best chance at success. 

 How do I route my fuel pressure regulator. 

There are a number of different ways to route a fuel pressure regulator. The way you route the system will depend on multiple factors including how much power you will make, what type of regulator you choose, what type of fuel rails and more. 

In all cases the manufacturers of the regulators will suggest the best way to route the lines. They have tested the installs of many vehicles to ensure reliable operation so if you are able follow these directions. Below you will see diagrams of common installs with a bypass regulator but once again we recommend to follow what the manufacturers suggest. Also to note we have not shown fuel filters in the system they will be required before the fuel rails and regulators. 

LS corvette style fuel pressure regulator 58psi. 

Bypass return style regulator before fuel rails install

Bypass return style regulator after fuel rails (best for boosted applications)

 Do I need a gauge for my fuel pressure regulator? 

While not necessary to have one especially once you have set your base pressure a gauge can help to diagnose issues in your fuel system related to pressure. There are a few different ways to install a pressure gauge. The easiest way is to install it in the built in gauge port that many regulators include. The other option is to use a gauge port adapter fitting found HERE. 

Just remember that a gauge will read pressure for everything that is in front of it, if you install your gauge before your regulator you will not read anything close to what the engine is seeing for pressure. 

As for what gauge to use we recommend the Aeromotive 0-100 for EFI systems found HERE. It has an equalizer button that takes temperature differential out of the equation so in a hot engine bay you always get an accurate reading. 

Also in HOSE 101 - Info on Hot Rod fuel hose and our products