What is the gain of running a return line from the fuel pump back to the tank versus just deheading it at the regulator?

You can't just run a return line, there's more to it than that. You need to set your fuel system up as a return system to use the return line. On pumps like the Magnafuel and Aeromotive, they must have the return line dump back to tank as there is no internal bypass and they will fail very quickly if deadheaded. I have my system set up as a return system, pump feeds regulators first, then line pressure is controlled by regulator at the end and whatever fuel isn't used is returned to tank. Look on Magnafuel's or Aeromotive's websites, they have a ton of info on this....

I feel a return style system is better, but there's arguments both ways and both are used successfully every day...

Pros and cons like Mark stated. I ran the 280 pump for years dead head. with no issues. Went to the 500 pump and still no issues. One thing to remember when running the return pump/system. Keep it as far away as you can from the suction side due to fuel return aeration issues.

I've run both deadheaded and return style with the same brand pump.
Had no problems with either setup. Gas or alcohol.
I've used Aeromotive A-2000 pumps on 2 different cars.
Present car has the same pump with their return style fuel log running gasoline.

Works fine and I went to the return style fuel log just feeling it would be better if I ran my alcohol carb but never have...yet....


The Aeromotive stuff has been very good for me....

I highly recommend the return style as it is much easier on the pump and the fuel stays cool.
With a deadhead if your pump is putting out 22 PSI that is what it is doing all the time burning up the pump and wasting energy.

With a return style if you have regulator set at 7 PSI then the pump is moving a good volume of fuel but it is not straining it.

Also with many of our cars there is heat under the car and the fuel can pick up some of that heat. With a return style it is constantly moving so you do not have that problem. It is easy to vapor lock a gas deadhead system here in Texas heat. Never have that problem with return style.

When I was running carbs, I used a return style regulator and simply ran it back to the tank. Return style for all the above posted reasons.

I now run injected alcohol with a belt driven pump. The fuel return goes back to the inlet side of the pump. Nothing gets returned to the tank.

My take on deadheading any pump is that it builds heat which can transfer to the fuel and that it shortens the life of the pump. Others will disagree and have run them for 50 years with no problems.