does a carbureted engine need a fuel return line

by Mr. Napoleon Heaney I Published 3 years ago Updated 2 years ago

Full Answer

Do I need a fuel return line for a carb?

Fuel return line for a carb? ie Carb to tank? In talking to some local guys and other sources, I'm being told having a fuel return to the tank from a carb will help its drivability and performance.

Where should the fuel return line be located?

The return line should direct fuel close to the bottom of the tank and away from the pickup. Why does it matter? Any restriction on the return side will create back pressure and limit the regulator's capability.

How does the fuel return system work?

With this system you run the feed line to the carb inlet line (fuel log) and on the other side of the fuel log is the inlet of the regulator. Then the return comes out of the regulator and back to the tank.

What is a free flowing fuel return line?

A free flowing return line maintains consistent pressure in the system. Ending the return above the fuel level in the tank, or in the filler neck will cause aeration. This can lead to fuel starvation and pump wear.

Is a return fuel line necessary?

You don't need it with a mechanical pump. Mechanical pumps supply fuel based on RPM, and so long as you're not running a big hipo mechanical pump, you're fine without a return. Edit: Keep in mind that the pump doesn't create pressure, resistance to flow does.Apr 26, 2012

What is the return line for on a carburetor?

It's primary purpose is to return excess fuel from the carburetor to the fuel pump, however it serves other important functions as well. Aside from providing a path for excess fuel to return to the tank, the fuel return hose also prevents vapor lock and over pressurization from occurring within the carburetor.Jan 8, 2016

What is the purpose of a fuel return line?

By removing the return box, you reduce the fuel temperature to prevent it from evaporating or vaporizing outdoors or when it is parked inside a warm environment. A fuel return line goes back to the tank of gas after collecting fuel. A high-pressure supply for the fuel injectors is necessary for fuel injection systems.Feb 15, 2022

Do you need a fuel return line on fuel injection?

Setting up fuel lines for fuel injection.

That's because almost all fuel injection systems require higher fuel pressures than a carbureted system, and most also require a fuel return line, not often found on a carbureted vehicle.Feb 12, 2021

Does a fuel pressure regulator need a return line?

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.Jan 12, 2017

Can you block off fuel return line?

Any fuel going through the return line is simply fuel your engine did not need/could not use. Blocking or restricting the line only increases fuel pressure at the injectors. Blocking the line results in the fuel pressure just being the maximum the pump can push.Sep 3, 2008

Why does a diesel have a fuel return line?

The reason is...

OK, The real reason for the fuel return line is that the extra fuel pulls heat off of the injector and makes it last a long time. Remember that the injector is in direct contact with the very hot cylinder head and combustion chamber.Jun 14, 2007

What causes fuel not to return?

The only things that are likely to cause fuel not to return are either a failed fuel pressure regulator, or an obstruction in the fuel rail.Jul 26, 2016

What size fuel line do I need for fuel injection?

Fuel pumps are sized to feed your system with enough fuel to optimize engine performance.
...
Recommended Size, Based on Horsepower.

Recommended Fuel Line Size (from the tank to the pump)
Engine Output	Size (inches)	Size (AN)
350 hp or less	5/16 in.	-5
350-450 hp	3/8 in.	-6
450-650 hp	1/2 in.	-8

1 more row

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Sep 16, 2017

What is Returnless EFI?

Returnless EFI systems typically operate at a higher pressure than return-type systems. This is necessary to reduce the risk of fuel boiling and vapor lock in the injector supply rail during hot weather (since there is no recirculation of fuel from the engine back to the tank to keep the fuel supply rail cool).

Fuel Return Line Size and Installation

When using a Return Style Fuel Pressure Regulator, it must be able to return 100% of the fuel back to the tank. The Fuel Return Line should be at least the same size, or one size larger than the supply. Make sure there are no sharp bends or kinks.

Why does it matter?

Any restriction on the return side will create back pressure and limit the regulator's capability. A free flowing return line maintains consistent pressure in the system.

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