Three Gas Line Puzzle

[jjackkrash]

We pulled the backseat out of our 2000 Am. Skier Volante, and either broke a valve off the reserve/main switching valve or it was already broken.  In any event, we noticed that there are three pickup tubes coming out of the tank, two of which go to the switching valve, and one of which is tied to the hose that exits the switching valve and heads back to the engine.  

Anyone know what that third hose is for and where it goes?  Its not the air vent, there is a fourth tube for that.  I'll try and post some pics if I can figure out how to.  

[jjackkrash]

Here is the tank.

[jjackkrash]

Here is the valve

[brandon]

I don't have a definite answer for you, but here is my guess.  One is the fuel feed to the valve, one is the reserve feed to the valve.  The third line on the valve should be the feed from valve to the motor.  The third line from the tank, directly to the motor??? may be a return line for a fuel injected motor.  Cars (fuel injected) have had return lines for a while, but I don't know when or if some boats did (I stopped working at a boat dealership in the beginning of the 2000 model year).  Ron should have the exact answer for you.

[jjackkrash]

The third line is tied to the hose that exists the reserve/main valve and heads to the engine.  My dad is in the boat bus., and he said diesels have a fuel loop that flows constantly and that the injectors just take what they need and the excess is returned to the tank. He said he has never heard of this on a gas engine.  We are both still stumped.  I'm about ready to pull everything up and just follow the two lines and see where they go to satisfy my curiosity.   

[RonT]

The third line you are referring to is a return line from the engine & operates like your dad thought. It just dumps back into the tank, the 2 supply pick-ups have tubes running down into the tank, the "reserve" reaches down into the "sump" part of the tank & the "main" is about 3" shorter. If the boat were mine I would eliminate the 3 way valve since nobody used them & use the the reserve or long pick-up as my fuel supply & plug the "main" supply. We had some issues with the system running on main & making sweeping turns causing the fuel to move away from the pickup whenever the tank was around 1/4 or less, the "reserve" pickup in the sump never has this problem. 

[jjackkrash]

Ron,

Thanks for the info.! 

[jjackkrash]

We decided to add a brass switch in the aft compartment rather than just disconnect it.  Now I can replace the key with a toggle switch and use this reserve/main tank valve as a security feature of sorts and simply cut off the gas when the boat is not in use. 

[jjackkrash]

Pic

[jjackkrash]

Pic

[jjackkrash]

Pic