View single post by Jim Ketcham
 Posted: 11-02-2006 03:30 am
PM Quote Reply Full Topic
Jim Ketcham


Joined: 03-13-2005
Location: Salt Point, New York USA
Posts: 192
You might want to look at the parts manual diagram.  I do not have one in front of me now, but I believe if you look at the names of the various components shown in the diagram you can figure it out.  For example, the spring loaded valve on top of the tank is called "pressure relief valve".  The line from it to atmosphere under the trunk, "pressure relief line".   The line from the tee after the pump to the top of the tank, "anti-syphon line".

You will notice that the "orifice" I believe you are refering to goes in the line to the carbon canister.

The SU style pump does not run continuously so does not need a place to dump fuel back to the tank.  That is why you hear it thump at different rates.  To test this just turn the ignition key to the on position.  You should hear the pump thump rapidly and then slowly and then stop (assuming your fuel system is in proper working order).  It regulates the pressure via a diaphragm and spring internal to the pump.  That is why you do not need an additional pressure regulator or a return line to the tank.

I am sorry if I made this sound complex.  It is not. The problem is my inability to explain it clearly.  Simply stated:

We have a fuel line to feed the engine at 2-3psi via a self regulated fuel pump.

An anti-syphon line teed into the above fuel line to the engine to break syphon when the engine is lower than the tank.

A vent line to equalize pressure to atmosphere in the tank (via the carbon canister)

A pressure relief valve and line to dump fuel if for some reason the tank builds up excessive pressure.