Katerina Swanson
The 3SGTE fuel return line is a component of the Toyota MR2, a car model with a dedicated community of owners and enthusiasts. The fuel return line is an important part of the vehicle's fuel system, and modifications or upgrades to this line are a common topic of discussion among MR2 owners. The stock size of the fuel return line is a matter of debate, with some sources suggesting it is 3/8, while others claim it is smaller, around 1/4. Upgrading the fuel return line can improve the flow of fuel in and out of the fuel rail, potentially increasing fuel pressure. When modifying the fuel return line, it is important to consider the potential for pressure build-up and vapour lock, and some owners have shared their experiences and advice on how to address these issues.
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What You'll Learn
The stock size of the fuel lines for the Gen 3 3SGTE
One forum user describes their experience fitting two 3/8 fittings on both sides of the fuel rail, tapping the out port on the fuel pressure regulator to accept the same 3/8 fitting. They also mention that the exit for the FPR back to the tank is 5/16. This user also plans to upgrade the line feeding the bottom side of the fuel filter to improve flow and avoid using banjo bolts.
Another user mentions that their fuel pressure for the Gen 3 3SGTE engine was set to 37 but has now increased to 40, and they seek input on whether this is a positive change. Other forum users agree that an increase in fuel pressure is beneficial if it remains consistent.
It is important to note that some forum users discuss upgrading the stock fuel lines, with one user stating that braided lines are only for show unless an FPR is being installed. Additionally, some users provide specific part numbers and fitting sizes for fuel line components, such as the stock filter, fuel rail inlet, and FPR, which are all mentioned as M12x1.25.
When it comes to running a fuel return line, some forum users provide guidance on converting the OEM feed line to a return line and connecting it to an upgraded pump. This involves drilling a hole on top of the fuel pump housing and sandwiching a fitting, such as an NPT to AN 90-degree angle, for the fuel return. The use of a 5/16" quick-connect fuel line is also mentioned.
For those seeking to perform a swap to a Gen 3 3SGTE engine, it is important to note that the stock fuel lines may not work, and a fuel line kit with appropriate adapters, washers, and fuel feed and return lines may be required.
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Converting to run a fuel return line
Another approach is to fit the appropriate fittings to the fuel rail and the fuel pressure regulator. For example, one user fitted two 3/8" fittings on both sides of the fuel rail and tapped the out port on the fuel pressure regulator to accept the same 3/8" fitting. They also mentioned that their FPR had a 3/8" fitting already in place for the exit port on the fuel rail, with the exit for the FPR back to the take being 5/16".
Upgrading the fuel pump and adding a return line is another crucial step in the conversion process. This involves drilling a hole on top of the fuel pump housing and sandwiching a fitting on, such as an NPT to AN 90-degree angle for the fuel return. The size of the fuel lines is important to consider, with the Spyder, for instance, using 5/16" quick-connect fuel lines.
Additionally, it is essential to address the standard regulator. One option is to machine a solid blank in the shape of the factory fuel pressure regulator to block pressure from bleeding within the tank. This can be done by ordering a part that clips on top of the factory fuel pump assembly and has a male -6AN connection. This allows you to use the VPS port as a return and run -6AN lines wherever needed.
Finally, it is important to consider the breather system to prevent vapour lock. One user suggested running a line from the tank to one of the smaller units on the canister, capping off the rest, and adding the return line.
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The stock fuel rail and improving fuel flow
The stock fuel rail of a 3SGTE engine can be improved by increasing the fuel pressure and flow. This can be achieved by upgrading the fuel pump, adding a return line, and deleting the evap sensors. Another option is to modify the stock fuel rail by boring it out to a larger size, such as 5/16". This helps to distribute the pressure better and improve the flow of fuel in and out of the rail.
One user on the MR2 Owners Club Forum reported that they fitted two 3/8" fittings on both sides of the fuel rail and tapped the out port on the fuel pressure regulator to accept the same 3/8" fitting. They also upgraded the main line from the tank to the filter and then from the filter to the fuel rail and back to the FPR, all using 3/8" hose. This modification improved the flow and may have increased the fuel pressure.
Another user on the same forum reported that they had increased their fuel pressure from 37 to 40 and wanted to know if that was a good thing. Other users confirmed that an increase in fuel pressure is a good thing if it's consistent.
A user on Toymods.org.au reported that the stock fuel rail for most EFI cars is not a limitation, and that the fuel lines feeding the fuel rail will usually be the first to introduce supply issues. They also suggested that if you are planning on upgrading the pump and fitting an aftermarket adjustable FPR, then you should have the rail bored out.
Another user on the same forum provided three solutions to improve the flow of the stock fuel rail for large injectors:
- Bore out the rail to 5/16"
- Modify the rail so the CSI output becomes the main input and have a dual return on each end of the rail
- Modify the rail to have a dual feed with the return in the centre
Finally, a user on MR2.com forums shared a DIY method to create a top-feed fuel rail for a 3SGTE engine. They used a top feed rail from a 5SFE engine, which has the same injector bores as any import-style denso injector, and cut the ends off the stock fuel rail, sealing the top feeders with an O-ring. They also had to make custom U-brackets for mounting and used a banjo to barb fitting to fit the stock return line.
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The OEM fuel feed line and fuel rail connection
The OEM fuel feed line is the original equipment manufacturer's fuel line designed to supply fuel from the fuel tank to the engine. It is important to ensure that the correct size and type of fuel line are used to maintain proper fuel flow and pressure. Most cars use a 5/16" feed line, but some older generations may use a 3/8" hose on both the feed and return lines.
When connecting the OEM fuel feed line to the 3SGTE fuel rail, it is recommended to use a 5/16" to 6AN adapter. This adapter allows for a secure and compatible connection between the fuel feed line and the fuel rail. The 6AN connection is commonly used in the 3SGTE engine setup and ensures a tight and leak-free joint.
It is worth noting that some modifications may be required to improve fuel flow and pressure. For example, adding fittings to both sides of the fuel rail can help enhance fuel flow in and out of the rail. Upgrading the main line from the tank to the filter and then to the fuel rail can also improve fuel flow and maintain consistent fuel pressure.
Overall, the OEM fuel feed line plays a critical role in supplying fuel to the 3SGTE engine. By using the appropriate adapters and making necessary modifications, a secure and efficient connection can be established between the fuel feed line and the fuel rail. Ensuring proper fuel flow and pressure is essential for the optimal performance and reliability of the 3SGTE engine.
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The fuel return line when installing a Gen3, Gen4 or Gen5 3SGTE engine
When installing a Gen3, Gen4, or Gen5 3SGTE engine, the fuel return line is an essential component to consider. The fuel return line is responsible for returning excess fuel from the engine back to the fuel tank. Here are some detailed instructions and considerations for the fuel return line:
First, it is important to note that the stock fuel lines may not be compatible with the 3SGTE engine. For a Gen4 or Gen5 engine, a complete fuel line kit is available that includes the necessary fuel return line and adapters. This kit ensures proper connections for both the fuel feed and return lines during the installation process.
For a Gen3 engine, the fuel line connects from the top of the fuel filter directly to the fuel rail. This fuel line is typically 3/8" with -6AN connections. It is recommended to use black fittings for this fuel line. Additionally, hose clamps are required if the operating temperature exceeds 150 degrees F or if the fuel line is used for oil or fuel systems.
When modifying the fuel return line, it is common to upgrade the fuel pump and add a return line. This may involve drilling a hole on top of the fuel pump housing and sandwiching a fitting to accommodate the fuel return. The specific fittings and sizes used can vary, but it is important to ensure compatibility with the fuel line.
In some cases, modifications to the factory fuel pressure regulator may be necessary. This can include blocking pressure from bleeding within the tank or upgrading to an external FPR. It is important to consult with experts or mechanics familiar with the 3SGTE engine to ensure that any modifications are safe and effective.
Lastly, consider the fuel return line routing back to the tank. One approach is to use the original feed line as a return and connect it to the 3SGTE fuel rail, running a new line back to the tank. This ensures that excess fuel is returned to the tank effectively.
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Frequently asked questions
The stock size is 3/8 hose on both sides.
The fuel return line is made of black fittings.
The operating temperature range is -40°F to 212°F.
The fuel return line for the Gen 4 or Gen 5 3SGTE is made of 6AN fuel line adapters.
You can drill a hole on top of the fuel pump housing and sandwich a fitting on for the fuel return.
