Mercury fuel pump suction thru anti siphon valve

[sbklf]

My tank is in the hull and the fuel line is uphill all the way to the motor (1998 Merc 200 HP carbed outboard). I installed new 3/8" fuel line with a primer bulb nearer to the motor (12' from the tank). Once primed, no problem but when shut off, the fuel in the line drains back into the tank. I Installed an anti siphon valve and it still drains back to the tank. I could blow backwards thru the valve so it is not positive shut off (not sure if is supposed to be?).

Couple of questions:

-I read about outboard motor fuel pumps having trouble with the added suction head with anti siphon valves, is this the case with Mercury fuel pumps?
-Will the motor run long enough on the fuel still in the bowls to allow the fuel pump to draw fuel thru the empty line and re-fill the bowls?
-If it will, since the line goes uphill all the way, can I remove the anti siphon valve?

Thanks, Kevin

 

[ENSIGN]

Re: Mercury fuel pump suction thru anti siphon valve

The valve should shut off completly, You either have a bad valve or a piece of crud stuck under the check ball.Remove and try to clean it with some carb cleaner and re-check it before you re-install.

 

[sbklf]

Re: Mercury fuel pump suction thru anti siphon valve

It is new, I did not know if they are supposed to have positive shut off or not.

 

[Dukedog]

Re: Mercury fuel pump suction thru anti siphon valve

The valve should shut off completly, You either have a bad valve or a piece of crud stuck under the check ball.Remove and try to clean it with some carb cleaner and re-check it before you re-install.[/QUOTE

Absolutly............

New primer blub? Aftermarket or OEM? Aftermarket is 50/50 on workin' right, even when new................

 

[sbklf]

Re: Mercury fuel pump suction thru anti siphon valve

I see the Quicksilver primer bulbs at West Marine, do they work better and have more positive shut off to prevent backflow?

If so, I will make some modifications and install one right at the tank.

 

[Chris1956]

Re: Mercury fuel pump suction thru anti siphon valve

Most built in tanks already have an A-S valve installed in the fuel pickup line. You might check yours to see if you already have one. You do not want two as this will be a restriction.

They seal both ways to keep from a) losing prime, and b) to keep fuel from siphoning into the boat.

 

[rodbolt]

Re: Mercury fuel pump suction thru anti siphon valve

if NO portion of the fuel system falls below the top of the tank anti siphon protection is not required.
your issue is WHY the fuel system has a primer bulb to start with.
Yamaha V6 motors for years came with a check valve between the lift pump intake and the engine filter housing to prevent drain back.
we eliminated them as they tended to give more problems than they solved.
why not simply prime the system with your fuel PRIMER bulb and go enjoy boating ?