John Burns Posted February 5, 2012 Share Posted February 5, 2012 Has anyone ever put a return on their fuel system? Winter gas combined with warm weather (50°+) is a recipe for vapor lock in my area. I'm in the middle of installing everything now. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted February 5, 2012 Share Posted February 5, 2012 use at least the same size line or larger than supply line Quote Link to comment Share on other sites More sharing options...
John Burns Posted February 5, 2012 Author Share Posted February 5, 2012 I thought I would need to do that based on a bunch of posts I saw doing a quick search. But it just didn't make sense because I am just trying to keep a little fuel flowing. What I found was that the big return line is needed if you are running a big electric pump and a bypass regulator. I'm running a 170gph mechanical pump- I asked Holley and this is what they told me: Install tee in fuel line from pump to carb. You will need a small restriction. may have to play with the restriction size to get proper fuel and pressure. Install restriction and run a line back to the tank for a return. It does not have to be large 1/4, -3 an. Does not have to flow a lot. If the restriction is too large, you will not have fuel volume or pressure. Soooo... I think I will still run a bypass regulator because I want max flow to the carb at WOT. There is a vacuum signal on the regulator that will close the bypass at WOT. I put it all together except for the line to the tank. Just to try it, I ran a 6 foot hose to a bucket. The problem is the pressure was jumping wildly at idle. Then I stumble upon Robb Mc- they have a "vapor return adapter". This is what he told me: Bypass regulators will cause the pressure to bounce at low engine speeds when using a mechanical pump due to the pulses coming out of the pump. The vapor return adapter fitting is a small brass fitting with a very small restrictor (about .030") inside. This allows a small amount of fuel to circulate back to the tank to reduce vapor lock and hot start problems. This is not the same as using a bypass regulator. It is simply a "bleed". So my plan is to use the small 1/4" vapor line back to the tank in the Monte. (That is what it is there for in the first place?!) And I'm going to use the factory fuel line in the Camaro as the return. Now I just need the time to do it all... Quote Link to comment Share on other sites More sharing options...
monte70car Posted February 5, 2012 Share Posted February 5, 2012 I had to add a return line for my EFI system. All I did was use a -6 an line all the way to the fuel sending unit which had a 1/4 return line made in it. Then again I'm pushing out a little more PSI then your pump. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted February 5, 2012 Share Posted February 5, 2012 with a bypass style regulator and too small of a return line, your fuel pressure may (mine did) go up because the pump is pushing more fuel than the return line can flow. you're not running a deadhead regulator anymore, and it's a long ways back to the tank, that's putting that much more load on your pump too Quote Link to comment Share on other sites More sharing options...
72MC Posted February 5, 2012 Share Posted February 5, 2012 Instructions for all return style regulators state the return line be "equal to" or "greater" than the supply line, period. One test that is to be performed after installing the regulator and lines is to run the pump with the regulator set at "zero pressure". This should cause your actual fuel pressure gauge to read no more than 3 psi. If it reads more than that, you have a problem with the return line in your set up. If your readings are in that range, then adjust the regulator to the desired pressure and your good. An electric fuel pump does work better with a return style regulator. - Dave Quote Link to comment Share on other sites More sharing options...
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