what does the anti-siphon valve do?

smokeonthewater

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Re: what does the anti-siphon valve do?

Yeah I'm thinking this is gonna turn out to be an ign or other electrical prob too but since the tank swap is so easy we can knock it out first...
 

mpdive

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Re: what does the anti-siphon valve do?

If I had a dime for every "get hot, act sporadic" ignition module I've replaced, I would have Don's money!:D:D:p
 

gss036

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Re: what does the anti-siphon valve do?

After reading the last few post, it reminds me of a problem my buddy had with his boat, but it is an I/O (w/350V8) and I think maybe the Merc outboard might also have one. His problem was with the SHIFT ASSIST MODULE. He finally totally unhooked it and his problem went away. If I remember correctly the shift assist module momentarily (for a split second) kills the engine so it shift easier. I could be wrong but worth a look I think.
So I think I would agree with the above posts that you are dealing with an electrical problem.
 

Beefer

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Re: what does the anti-siphon valve do?

Not 100% sold on it being solely an electrical problem. If it only cut-off as he describes, then yes, but he is also saying that there are time where the rpm's drop way down unexpectedly, which leads me to still think fuel. I do think there is the potential for 2 problems (one electrical, one fuel).
 

gss036

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Re: what does the anti-siphon valve do?

Not 100% sold on it being solely an electrical problem. If it only cut-off as he describes, then yes, but he is also saying that there are time where the rpm's drop way down unexpectedly, which leads me to still think fuel. I do think there is the potential for 2 problems (one electrical, one fuel).
I can go along with that. I used to have a 200 hp Mercury for 20 years. The only interment problem I encountered was with the wiring harness plug that is located to the starboard side of the engine. It was so corroded that the mercury mechanic said if it were his engine he would cut it out of the system and wire directly since if I ever changed engines I would need a new wiring harness. We did that and it worked great for several more years until I blew the engine. Pull the plug apart and clean it up good and plug it back in. Just another possibility. I now have a 225 Honda and love it.
 

mpdive

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Re: what does the anti-siphon valve do?

What bothers me is the fact that it could do it at any time, any rpm, any load. Usually fuel problems show themselves at certain load conditions, certain speeds, certain cold start scenarios or within a constant parameter. I remember the Ford processors and Chryslers that would do the same thing. I had customers tell me the car would just stop. I could never find nothing wrong till I had to leave the shop one day and rescue the person. Got there and it started right up. Started driving it back to the shop and it cut right off. Started right back up. Got it back to the shop and it stopped and wouldn't restart. Put 6 ice cubes on the module and bam, fired right up. Replaced the module and never heard from them again. Quite aggravating. I just added to a post for the 1989 Merc about a lake test. The same may apply here.
 

GlasV162

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Re: what does the anti-siphon valve do?

Thank you thank you guys..........I really appreciate the input.

I'm going to try the remote tank this weekend and will report back how it goes. We've run at least 150 gallons of gas through it since we've owned it (new to us this season). The guy we bought it from said he used it frequently.......whatever that means. After we bought it I took it right to our Merc dealer for a check-over and he told me he found gelled fuel in the VST and cleaned it out. Several times this season, I've removed both filters and emptied the contents into clear glass containers and there never was a trace of water or other contamination. It was always the same color all the way through.

For work done on the motor, I had hydraulic steering installed, and the dealer had to remove the motor and raise it a notch to allow for clearance of the hydraulic cylinder. I also had the fuel injectors cleaned last month ($1,000) as the dealer told me that was the cause of the stalling; it didn't fix the problem.

Don't fuel pumps simply quit without warning? In cars I've owned, the fuel pump simply dies and never comes back to life; are outboards different?
Thanks again guys--I really appreciate it; running on the portable tank should help me eliminate a few possible problems.
 

Beefer

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Re: what does the anti-siphon valve do?

What bothers me is the fact that it could do it at any time, any rpm, any load. Usually fuel problems show themselves at certain load conditions, certain speeds, certain cold start scenarios or within a constant parameter.

My fuel problem occurred at different conditions. Sometimes it would die 2 minutes after starting, and sometimes I could run for an hour and not have a problem. Sometimes at 3800rpms, sometimes it would die before reaching 2500rpms. My problem was a clogged fuel pick up screen, and sometimes it was able to allow enough gas for whatever I demanded, other times it would suck up just enough crap from the tank to cut out fuel flow. It happened more frequently during choppy water, but would happen in smooth water as well.

Thank you thank you guys..........I really appreciate the input.

I'm going to try the remote tank this weekend and will report back how it goes. We've run at least 150 gallons of gas through it since we've owned it (new to us this season). The guy we bought it from said he used it frequently.......whatever that means. After we bought it I took it right to our Merc dealer for a check-over and he told me he found gelled fuel in the VST and cleaned it out. Several times this season, I've removed both filters and emptied the contents into clear glass containers and there never was a trace of water or other contamination. It was always the same color all the way through.

For work done on the motor, I had hydraulic steering installed, and the dealer had to remove the motor and raise it a notch to allow for clearance of the hydraulic cylinder. I also had the fuel injectors cleaned last month ($1,000) as the dealer told me that was the cause of the stalling; it didn't fix the problem.

Don't fuel pumps simply quit without warning? In cars I've owned, the fuel pump simply dies and never comes back to life; are outboards different?
Thanks again guys--I really appreciate it; running on the portable tank should help me eliminate a few possible problems.

The gelled fuel is like what I mentioned earlier about the older non-ethanol fuel being affected by the new ethanol blend. Kind of sounds like your state used to use MTBE in their fuel, which will coagulate when mixed with the ethanol blends. I know I've said it 2 times already, but check your pick up tube screen. That gel may be coating it, which would be a deja vu of my problem. You wouldn't necessarily see it in the filters further down the line.

Some fuel pumps have a rubber diaphragm, which will deteriorate/leak, and could cause your problem also. Boats have either mechanical or electric fuel pumps, whereas today's cars have electric. So a car's pump will just die and never work again, whereas a mechanical pump can have a slow death. I think you have an electric pump, so I doubt (now) that it's your problem, unless you have a bad electrical connection to an otherwise good pump.
 

mpdive

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Re: what does the anti-siphon valve do?

They can go out both ways. When they don't fully fail, the diaphram pressure decreases as does the fuel pressure. If you can get out on the water, run it on a remote tank. I would run with the doghouse removed and the arrestor removed. First sign of it cutting out I would give a short blast of carb cleaner in the venturi. If you get an rpm return it is fuel related. It's an easy diagnosis from there.
 

mpdive

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Re: what does the anti-siphon valve do?

Good point Beefer. Another good reason to run off a remote.
 

jimbo_jwc

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Re: what does the anti-siphon valve do?

Don't large outboards use vacuum diaphram pumps with built in check valves ? My old O/B boat had primer bulb w/checks and hose hook was higher than tank . The tank must have not had antisiphon valve because I used to uncoil and put hose without chyrsler check fitting through bottom drain to remove the last years fuel .
 

GlasV162

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Re: what does the anti-siphon valve do?

We tried the boat today w/ the remote tank and got the same results--within minutes of warming up, it stalled several times and would also start right up again. When it would lose power, I didn't move the throttle at all, and the rpms would drop, then pick right up again. If I pulled the throttel back to neutral upon loss of power, it would stall. Still a mystery, but at least we ruled out a problem w/ the built-in tank. Any thoughts??
Thanks,
John
 

mpdive

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Re: what does the anti-siphon valve do?

We tried the boat today w/ the remote tank and got the same results--within minutes of warming up, it stalled several times and would also start right up again. When it would lose power, I didn't move the throttle at all, and the rpms would drop, then pick right up again. If I pulled the throttel back to neutral upon loss of power, it would stall. Still a mystery, but at least we ruled out a problem w/ the built-in tank. Any thoughts??
Thanks,
John

I'm still thinking ignition module. It has all the classic signs. There are no fault lights lit up on the dash is there? Has it been checked for codes?
 

GlasV162

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Re: what does the anti-siphon valve do?

mpdive,
I'm not sure, but I'll ask my Merc dealer tomorrow a.m. I'm bringing it back to him. Still the same exact symptoms that it had before they cleaned the fuel injectors. Should this go to a Merc forum at this point?? Thanks again,
John
 

Beefer

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Re: what does the anti-siphon valve do?

So what's the verdict - if any?
 

GlasV162

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Re: what does the anti-siphon valve do?

Hi,
Stopped at the dealer this a.m. and they weren't able to duplicate the problem. They said they took it to the lake and it ran great, also used a "test wheel," whatever that is. This is the 3rd time back, over $1,000.00 spent, and still the same problem. While I was at the shop this a.m. the tech came out to speak with me but then the owner came out and yelled at him to get back in the shop. Any advice??
 

smokeonthewater

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Re: what does the anti-siphon valve do?

we gave a LOT of advice already.... did you do any of it? ALSO tell that dealer to take a flying leap.... If the owner would have done that in my presence he would have either apologized to me and the tech or ordered me off the property..... I would have climbed all up and down his.... uh....... donkey
 

GlasV162

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Re: what does the anti-siphon valve do?

I picked the boat up today and will not likely go back to that shop--another $120.00 for them to tell me it's running fine and they can't find the problem. This season alone, we've spent over $3500.00 there on service work; apparently that's not enough to have a few minutes of the technician's time to try to help him find the problem.

I've tried what I know to do myself; unfortunately, I know just enough to be dangerous; therefore if I'm going to own a boat, I have no choice but to trust who's working on it. Thanks to all of you again for the help.
John
 

smokeonthewater

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Re: what does the anti-siphon valve do?

well you either need to start trouble shooting such as trying a remote tank OR you need another shop.... Find a tech and tell him you'll pay him $100 and buy dinner to go boating with you all day and find the problem LOL

Maybe post your location and some nice local iboater might take you up on such an offer
 

GlasV162

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Re: what does the anti-siphon valve do?

I tried the remote tank (see previous post on 9-25) and there was no difference; the stalling continued. That's about as far as I dare go on my own; beyond that, I have to trust what the shop personnel are telling me. Or, in other words, it's time to get out of boating.
 
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