VST return line (help-thoughts)
 

WE all know about the vapor lock issues with 502 mpi's & 454mag mpi. Had a known marine eng. builder say run the return line from the VST back to the fuel tank instead of where it goes now which is just the vst resevior. Thus, always bringing in cool fuel and dispersing any air.
Said take it back to one of the vent outlets on the tank, since I have (2)..
Thoughts.......................................

Will work great as long as the tank has enough venting through the one remaining vent. The vent should be 5/8" to properly vent the tank.
If the vent line isn't large enough to vent the tank, then you can always add a return to the tank. It's pretty easy to do without welding. Let me know if you need help with it.
Eddie

Why not just run it to the fill line with a "T"?

I've run into a ton of boats where the fill hose is all the way at the front of the tank and not easily accessible. Obviously, if it is easy to get to then it's a very viable solution.
Eddie

I ideally the return should be directed below the fuel level in the tank so it does not aerate the fuel. An extra pickup is good to use as long as the bottom of your tank is clean.

sorry but i can't believe this is a good idea... first of all the return has to be to an unrestricted location. any restriction in the return changes the fuel pressure in the rail and the pressure the bottom of the fuel tank aganst that line while low, is still meaningful. more importantly the return fuel will always be trying to move that column of fuel thats in that line because that fuel is always trying to seek the overall level of the rest of the fuel in the tank and that will simulate a big restriction...

ideal location and the one every oem installation uses is back to the top of the tank in one fashion or another.

merc did theirs as a loop for packaging reasons only and if the engine compartment can be kept from being like the surface of the sun then it will actually function...

but in the real world that is seldom the case...

won't work with multiple fuel tanks. return will act as transfer pump emptying the tank being used into tank with return plumbed to it. more of an issue in the sportfish world than here, but it is worth mentioning.

well... in this case the term " won't work" is relative.

if its done incorrectly then yes... it won't work. like most things

but if its done correctly and in a manner appropriate with the rest of the fuel system configuration then not only will it work, it will solve his problem.

If you are going to return it to the tank don't do it near the fuel pick-up in the tank to prevent aeriation.

When I eliminated the VST. I could not run the return line to the tank due to multiple tanks and fuel flow meters. Instead I ran the return line to the suction side of the lift pump, added another lift pump between the tank and the existing lift pump, and used a power steering cooler as a fuel cooler. So far so good.

Steve