Problems with anti-siphon valves?

[Ole Joe]

Has anyone had experience with this?

This winter I installed a new fuel system. The tank manufacturer ships the tank with an anti-siphon valves installed in the pick-up tube fittings. Now my Johnson/Susuki DF 140s do not pick up at fuel after it reaches 1/2 tank level. I suspect it is because of the valves. All new hoses, filters, water separators installed at the same time. Pick-up to engine distances are shorter than before, the lifts less as well, the vent is clear, and the bulbs have fuel in them when the failure occurs.

After refilling the tank, engine performace is fully restored. Ran 20 minutes at 4,700 RPMs without any fuel starving, then shut down to idle and resumed normally maneuvering. There are no restrictions in the lines other than the anti-siphon valves, so they will be replaced with straight through barb fittings.

Has anyone encountered this?

[tsturm]

Yes, I knock the ball out & make it straight through.

[Ole Joe]

Tsturm,
Thanks for the prompt response. I felt certain that was the problem, except that I read reports of the poly pick up tube leaking air into the system where it joins the 90 degree aluminum fitting.

I plan to knock the ball, spring, and retainer out tomorrow. While in there I guess I'll pull the pick up tube and check it's connection.

[Moonlighter]

It doesnt sound like an AS valve issue to me.... but i would still get rid of it. With AS valve fails, the bulb is always empty when the engine starves.

Sounds more likely to be an issue with tank pickup. It would be strange but with a new tank Thats where I would look, maybe there is a hole half way down or they installed the wrong pickup tube and its too short...

Good luck let us know what you find. Its always helpful to hear the result so others can learn.

[Ole Joe]

I spoke with the manufacturer's chief engineer this afternoon. He also suspects the pick-up tubes, says the AS valves should not do it. Also, because both engines fail at the same time it points him toward the tubes.

He is aware of the poly aluminum connection issue and said that he would not think a new system would fail. He indicated that it seems to take a couple years before this occurs. They do not know why the poly tube is becoming brittle. Thinks it might result from using one of the fuel additives, but they have not been able to duplicate it in the lab. Said the tube can get like a piece of straw.

Am planning to knock the ball assembly out of both valves and pull the tubes. Am leaving town for a few days. When we return, I will pull them and give you an update.

[Ole Joe]

Since my July post I have been running off the top ½ of the tank since we are only fishing the back bay this season. It had been my intention to finish out the season and then remove the AS valves once I had the boat home. However, I did remove the AS valves last month but continued to run off the top portion of the tank.

Yesterday I realized that it would be foolish to tow the boat all the way home with more than a half tank of gas in it…only to pump it out once there. So, I made a couple long runs in the back bay and removed the gas down to just below the ½ full mark. I am glad to report that, with the Anti Siphon valves removed, the motors perform exactly the way they should. There is no starving at either high RPM or low RPMs.

I also have confirmed that the pickup tubes are the proper length. There is a fuel return port fitting in this tank in addition to the two pick up tube fittings. I removed the return port cap and, using a length of coat hanger, was able to chase both pick up tubes to the bottom of the tank by feel.


So, unless I experience some starving as the fuel level drops further, I believe the problem is behind me.

Thanks to all who offered advice and suggestions.

[bklake]

I had a similar fuel starvation problem. Half tank of less, started running bad or wouldn't start up. I was convinced it was the anti siphon valve. Those things are stunningly difficult to find new.

Long story short, when I removed the fitting I found it was cross threaded. After about 3 years, the sealant on the fitting started to break down and was sucking air. Check that.

[Ole Joe]

Thanks for that.

Hard to believe.some of the stuff that gets past the quality controls. You know the guy that put that in knew he cross threaded it and still let it go down the line.

Was it a Moeller Tank?

[bklake]

Built in tank, don't know the brand. Chaparral boat. It was a peach to fix. Had to re-tap it with about an inch of working space. No other option.

As an aside, I knew a guy that worked in the marine industry for 50 years. When he was working at a high end fishing boat manufacturer, he had a chance to deliver a new boat. The first thing the dealer did was send the mechanic out to remove the anti siphon valves and replace them with barbed fittings. The mechanic would throw the valves as far out in the water as he could so nobody would reuse them. The dealer said the valves caused more problems than they solved. He was shocked because a big part of his job was to ensure the boats were built in compliance with regulations. They dealer was more concerned with his customers not getting stranded 80 miles off shore. He used his contacts in the industry to find me a new anti siphon valve. The size I needed was unusual. It is in my tool box somewhere. I used a barbed fitting temporarily so I could get back on the water. It's been ten years, I'll get around to it one day.

[Ole Joe]

Great story, but I gotta ask...knowing what you know now...well, never mind, maybe another 10 year wait won't hurt.

[Moonlighter]

Anti syphon valves aren’t required on outboard powered boats in the USA.

And to my knowledge, nowhere else in the world requires them for outboard powered boats either.

[Ole Joe]

bklake,

Following my July 6 conversation with the manufacturer (Moeller), their engineer sent me a new AS valve to replace one that sheared of during removal. I did not install it because it arrived a week after I had completed removal and replacement with straight thru barb fittings. My intention was to install it after drilling out the ball and seat assembly.


Come to think of it, just as insurance, I'm gonna follow your lead and put it in the tool box instead. With that, I can rest easy for the next 10 years.

[Moonlighter]

I helped a friend who imported a US made boat into Australia to sort out his AS valve issue.

Unscrewed it from the tank, took it to the workbench, and used a nail punch and hammer to punch its internals out. There is just a ball, spring and seat in there. No drilling involved.

[Ole Joe]

Thanks for that Moonlighter. Most of the posts that I've read by others indicate that they punched it out as you did. Works either way.

My darn fittings are made of aluminum and I did not want to bang on then because the auminum is so tender. I drilled using a drill press combined with a table vise that holds the piece for precision boring. I simply bored out the seat and the internals fell out.

[Ole Joe]

Moonlighter,

One more thought on this topic. I post this not as critisim, but to furnish more info for other members to gain from my experience.

In your first post, you said, "With AS valve fails, the bulb is always empty when the engine starves." The tank manufacture also did not think it would be the AS valve and he also felt like it would be a problem with the pick up tubes. However, this is not true in my case.

In my case, the replacement of the AS valves with straight thru barb fittings definately cured the problem. I have run the engines the last couple days with the fuel level below the 1/2 full mark at 4,200 - 4,400 RPMs without starving and at 700 RPM idle all with normal engine performance.

I assume the AS valves created just enough resistance that the primary pumps could not lift the fuel at idle and created momintary starving at 4,200 RPMs. When they stopped lifting, the fuel remained where it was in the lines and the bulbs. That is just a guess on my part, but the removal of the AS obstructions cured my problem. Maybe my pumps are weak. They are original (2003) and have not been rebuilt. This winter I'll pull them for service.

I want to thank you and the other members for offering your thoughts and advice.