Mercruiser 7.4 VST - Fuel out of Vent

[bigwhite]

Finally the boat is running....

The Vapor Seperator Tank has fuel coming out of the side vent line. Like a steady stream of 1 cup every 30 seconds.

I have pulled the VST cleaned, changed the diaphragm, and cleaned the needle valve. Everything cleaned again and reinstalled.

Any ideas?

I am tired and this thing is wearing me out.

 

[alldodge]

The VST is just like a carb bowl. It has a float, needle valve and seat. If the float is not adjusted right, the needle and or seat is not sealing off incoming fuel, it will over flow. Either the needle and seat.

If you replaced the fuel pump that feeds the VST is it a low pressure one and not a high pressure?

 

[bigwhite]

Float looks perfect, needle and seet seem perfect, no sediment or residue in tank, no adjustment possible on the float.

Out of the lower fuel pump (cool fuel system) before it enters the VST fuel pressure is right at 40 PSI

I have a extra pump and it seems to be the same.

What PSI should it be entering the VST tank?

Everthing came from a working running motor.. Is it wrong?

 

[alldodge]

Out of the lower fuel pump (cool fuel system) before it enters the VST fuel pressure is right at 40 PSI

This is way to high, it should be no more then about 10 psi and that would be high. You should not have a cool fuel for the primary pump, it should be low pressure mechanical pump. The VST was changed to cool fuel in the next Gen. Your motor can be changed over to cool fuel but the VST has to be removed

Airtex pumps
Electric fuel low pressure E11003
Electric fuel high pressure E11004