what does the anti-siphon valve do?

[GlasV162]

Re: what does the anti-siphon valve do?

smokeonthewater, the symptoms are intermittent stalling after warm-up (1999 Merc 150 EFI). It starts fine cold, runs great and then after leaving the dock it will simply quit without warning. It starts right up again after it dies and off I go until the next time it stalls. It will do this in any condition (rough / calm) and at any RPM. Someone told me it could be a faulty anti-siphon valve, so I thought I'd have a look at it. I can do some things myself, but others I have to rely on a marina. I brought it to them with theses symptoms and they told me it was a clogged fuel injector, so I had them cleaned; $1,000+ later, I still have the same symptoms. Thanks for the help.

 

[Krichbourg]

Re: what does the anti-siphon valve do?

... , And had hoped a blow job could amost fix everything !

No truer words have ever been spoken. Now, back to talking about boats.

Couldn't help it!

 

[Beefer]

Re: what does the anti-siphon valve do?

smokeonthewater, the symptoms are intermittent stalling after warm-up (1999 Merc 150 EFI). It starts fine cold, runs great and then after leaving the dock it will simply quit without warning. It starts right up again after it dies and off I go until the next time it stalls. It will do this in any condition (rough / calm) and at any RPM. Someone told me it could be a faulty anti-siphon valve, so I thought I'd have a look at it. I can do some things myself, but others I have to rely on a marina. I brought it to them with theses symptoms and they told me it was a clogged fuel injector, so I had them cleaned; $1,000+ later, I still have the same symptoms. Thanks for the help.

If you haven't already, check/replace all of the fuel filters. Also check/clean/replace/remove the screen inside the pickup tube in the fuel tank. If your tank is located beneath a deck panel, there should be access to the sending unit and the fuel pickup via a deck pie plate. The check valve is typically the fist connection between the pickup and the fuel lines. It looks like a barbed fitting with a spring-loaded ball inside of it (you have to take the fuel line off the pickup and look in the fitting to see it).

Mine looks like this (3/8" lines):

Yours may look like this (1/4" lines):

 

[smokeonthewater]

Re: what does the anti-siphon valve do?

an EASY test is to hook up a portable 6 gallon tank and see if you keep the problem.

 

[gss036]

Re: what does the anti-siphon valve do?

I learned about the anti siphon valve when I had to replace my fuel tank a couple years ago. I used to able to start a fuel flow with a a primer bulb and it would continue to run. I did this for gas for my lawn movers-generators, etc. When I tried on the new fuel tank, it would only flow as long as I squeezed the primer bulb. Good exercise for the hand muscles though.
I have duel outlets on my 75 gallon tank and if I could find a "cheap" shut-off valve I would install so I would a have readily available to fuel for my generator in the winter if needed. Could I use a propane shut off vale? They are about 1/2 the price of gasoline ones? Just a thought

 

[Frozen]

Re: what does the anti-siphon valve do?

i can not blow from the fuel pump to my tank. My anti-siphon closes. It only opens when there is a vacuum on it. So thats wrong?

 

[jimbo_jwc]

Re: what does the anti-siphon valve do?

I learned about the anti siphon valve when I had to replace my fuel tank a couple years ago. I used to able to start a fuel flow with a a primer bulb and it would continue to run. I did this for gas for my lawn movers-generators, etc. When I tried on the new fuel tank, it would only flow as long as I squeezed the primer bulb. Good exercise for the hand muscles though.
I have duel outlets on my 75 gallon tank and if I could find a "cheap" shut-off valve I would install so I would a have readily available to fuel for my generator in the winter if needed. Could I use a propane shut off vale? They are about 1/2 the price of gasoline ones? Just a thought

I have one currently plumbed to a fulflow filter fuel oil furnace w/ chyrsler hose bib w/check and squeeze primer ball w/check and it is sitting higher than oil burner in Fce and was supprized it has run about 3 fillups at 6gall with no problems . Only tempory till I sandblast and paint . I

 

[Beefer]

Re: what does the anti-siphon valve do?

an EASY test is to hook up a portable 6 gallon tank and see if you keep the problem.

Only potential problem with this is if the person testing connects the fuel line from the fuel cell (boat) to the portable, and doesn't change the anti-siphon with a regular barbed fitting. But yes, using a portable helps tremendously in determining a fuel issue.

 

[mpdive]

Re: what does the anti-siphon valve do?

In response to Frozen. No. Fuel pump suction unseats the check ball. Loss of suction resets the ball. Hence the safety aspect. If the fuel line is compromised, suction is lost fuel flow stops.

 

[GlasV162]

Re: what does the anti-siphon valve do?

So, in my case with the motor stalling intermittently, does that sound like a faulty anti-siphon? I can prime the pump no problem, it starts and runs fine when cold, but then it will stall without any warning, at any time, under any conditions and RPMs. Thanks,
John

 

[mpdive]

Re: what does the anti-siphon valve do?

So, in my case with the motor stalling intermittently, does that sound like a faulty anti-siphon? I can prime the pump no problem, it starts and runs fine when cold, but then it will stall without any warning, at any time, under any conditions and RPMs. Thanks,
John

Best thing to do John is run it on a portable tank from the pump. This way you can tell if it's carb related or if there's a problem from the tank to the pump. Process of elimination and not emptying your wallet unnecessarily.

 

[mpdive]

Re: what does the anti-siphon valve do?

So, in my case with the motor stalling intermittently, does that sound like a faulty anti-siphon? I can prime the pump no problem, it starts and runs fine when cold, but then it will stall without any warning, at any time, under any conditions and RPMs. Thanks,
John

What do you mean by stall? Will it stall at cruising speed under a slight load? Does it backfire when it shuts down? Does it start right back up again, and if not, what is the restart procedure?

 

[Fed]

Re: what does the anti-siphon valve do?

So, in my case with the motor stalling intermittently, does that sound like a faulty anti-siphon?

No.

 

[ssobol]

Re: what does the anti-siphon valve do?

Long time ago a friend had a boat with a similar problem. It was a new boat and it would run ok most of the time but periodically it would just quit (could be idling, could be running full out). Sometimes it would start right up, sometimes it would take some cranking and fiddling to get it to run again. After checking the fuel system and stuff we eventually found a partially pushed pin in the connector for the remote controls. The connector was molded so it was not easy to fix the one pin. Put a little ball of foil in the socket for this pin and put the connector back. No problems after that.

 

[GlasV162]

Re: what does the anti-siphon valve do?

mpdive, when I say it stalls, I mean it just shuts off. Dead. I pull the throttle back to neutral, turn the key and it starts right up again. This will happen at any RPM, calm water, rough water, pretty much whenever. A couple times this past Sunday I thought it was going to stall but it just idled way down and then RPMs went back up again without stalling, but 99% of the time, it simply shuts off. No backfire, no alarm. BTW it's a '99 Merc 150 EFI. Thanks for all the help.
John

 

[Beefer]

Re: what does the anti-siphon valve do?

How old is the fuel? If it's an older boat, the walls of the fuel cell may have 'shellac' build-up from the previously used non-ethanol fuel, and now the newer ethanol fuel is cleaning that from the tank and it's clogging/restricting your fuel system. Seeing as it's a '99, this is a possibility. This can cause intermittent stalling and RPM loss without consistency.

Like I said before, check all your fuel system filters and screens. Then check your fuel pump for issues.

A couple times this past Sunday I thought it was going to stall but it just idled way down and then RPMs went back up again without stalling, but 99% of the time, it simply shuts off. No backfire, no alarm.

The first part of this statement sounds like a fuel delivery problem, but the second half sounds electrical. There is the possibility that you have more than one problem. Get to the boat, and hook up a portable tank, and narrow it down to boatside or tankside. If you don't do that, the number of possible causes are endless.

 

[smokeonthewater]

Re: what does the anti-siphon valve do?

Yep, unhook the tank at thhe fuel pump and PLUG THE HOSE.... then hook a hose from a portable tank to the pump.... I'll bet you dollars to doughnuts that it makes no difference but try this first and let us know how it goes.

 

[Beefer]

Re: what does the anti-siphon valve do?

Yep, unhook the tank at thhe fuel pump and PLUG THE HOSE.... then hook a hose from a portable tank to the pump.... I'll bet you dollars to doughnuts that it makes no difference but try this first and let us know how it goes.

To add -

And what you'll learn if it makes no difference, is that the problem isn't: the fuel being used, the anti-siphon valve, the pick-up tube, the pick-up tube screen, the fuel line between the tank and the fuel pump. It will narrow it down. If the problem goes away, then it's (probably) one of the things I listed.

If it does continue, check the fuel pump, and work your way through the system (including the lines).

All this is assuming you have checked all your fuel system filters. Have I said that already....???

 

[mpdive]

Re: what does the anti-siphon valve do?

mpdive, when I say it stalls, I mean it just shuts off. Dead. I pull the throttle back to neutral, turn the key and it starts right up again. This will happen at any RPM, calm water, rough water, pretty much whenever. A couple times this past Sunday I thought it was going to stall but it just idled way down and then RPMs went back up again without stalling, but 99% of the time, it simply shuts off. No backfire, no alarm. BTW it's a '99 Merc 150 EFI. Thanks for all the help.
John

I would try the remote tank, but I think I would verify fuel pump pressure first to be sure your not dealing with an ailing pump. However, when an engine shuts down and it's fuel related, it's usually accompanied by either a lean or rich backfire condition. This is because spark is still there but the fuel supply is shorted for combustion. If it simply just shuts off, I am wondering if you don't have a sporadic ignition problem going on here. If it was starved for fuel it would not fire right back up. Additionally, if it fires right back up, it's awful hard to diagnose a primary or secondary ignition problem. Have you recently done anything to the boat in an area where you may have moved some wires around?

 

[mpdive]

Re: what does the anti-siphon valve do?

I don't know why but after reading the original post of it acting up when warm, subliminally something is telling me failing ignition module......