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Returnless Fuel System

A look at the difference beteween Returnless and Return Type Fuel Set-ups

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Returnless Fuel Systems are starting to be installed more and more each year by OEM manufacturers on EFI equiped engines. It seems important then to know what they are and the difference between this type of fuel system, and a return type fuel system that we are all used to.

Return Type Fuel System

A return Type fuel system starts with a fuel pump mounted in or out of the tank. Then flows the fuel down a supply fuel line to the fuel rail or rails depending on the application. At the end of each rail is a Fuel Pressure Regulator that regulates the fuel pressure. From the fuel pressure regulator, any excess fuel flows back to the tank in a return fuel line. This set up is great for keeping the systems pressure stable, and the fuel pump cool, being that there is a constant flow of fuel flowing through the pump at all times.

Return Vs Returnless Type Fuel System Gas Supply Fuel RailReturn Vs Returnless Type Fuel System Gas Supply Fuel Rail Pressure Regulator

Returnless Type Fuel System

A returnless type fuel system consists of only a fuel pump with a voltage regulator, a fuel supply line, and finally ends up in the fuel rail. The pump then constantly is pushing fuel up line at a given pressure based on the strength of the pump. The pump strength is regulated by the amount of voltage the pump is supplied with. Instead of the pressure being regulated then by a Fuel Pressure Regulator, the fuel pump itself regulates the pressure. Also manufacturers mount a bypass valve on the supply line in the pump so that the pump can bypass fuel right back into the tank if there happens to be more flow than the fuel line can tank.

Return Vs Returnless Type Fuel System Gas Supply Fuel Rail

Why have manufactures made the switch?

There are two main reasons manufactures are starting to switch over to returnless type fuel systems.

1. They are cheaper. Eliminating the Fuel Pressure Regulator, and the return fuel line.

2. More Compact. Only having to run one fuel line instead of two gives you many more options for design. Also the fuel rail is more compact not having to have the regulator mounted on it, and there is no need to run a vacuum line to the regulator since it doesn’t exist.


Both systems do the job they were intended to do, but when it comes to wanting extremely high amount of flow for high horsepower applications, most shops are finding that they have to ditch the returnless fuel set-up, and go to a return type system.


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