Fuel tank anti siphon valve questions

[barnstormerj]

After solving the wrong carb problem, I find that my fuel pressure is less than 1 lb . I took out the anti siphon valve and replaced with threaded nipple at the gas tank, and low and behold, we now have 3 lbs fuel pressure. Question is, do I replace the anti siphon valve with a new one, or could the fuel pump be weak enough to cause this? we know we have to have anti siphon valve for safety, coast guard spec, but the electric fuel pump in my estimation could be weak enough to cause the problem. I put a holley regulator, and a fuel pressure valve in line to the carb. who has run into this problem before? I can blow through the anti siphon valve, but it seems a little restrictive, seems like someone said to hook up a clear plastic hose to the valve, the threaded side, and see if 25 inches of water in the line will flow and 20 inches of water in the line will not. Is that a viable test?

 

[Borchik]

Put a new valve in to be sure but i would also replace the fuel feed line and make sure you have no other possible locations for an air leak such as a cracked fitting at the fuel filter or anything like that. If everything is ok i would bet your fuel pump is on its way out.

 

[barnstormerj]

Thanks, that was my plan,but ie always helps to get some input from other mechanics.

 

[barnstormerj]

Thanks, that was my plan,but ie always helps to get some input from other mechanics.

 

[barnstormerj]

O.K., now , have installed new fuel pump, mounted it separate from engine to allow for less chance of vapor lock, seem to have plenty of fuel, at least it fills up the visible fuel filter I have installed after the regulator and before the carb. my boat does have a new screw on filter directly after the tank, a water separator from OMC that was orig equip, will check for cracks, and for other defects . But for now, everything is o.k..

 

[Howard Sterndrive]

1 psi at idle? yeah, definitely a pump problem - not the anti siphon at fault there

3 psi now at idle? still iffy. However, fuel pressure at idle is of very little value, the typical 4-7 psi spec is for running under load on plane when you boat is drinking several gallons per hour of gas.