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Fuel Line anti-siphon needed on a 58 Connie?

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bobbystone
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Fuel Line anti-siphon needed on a 58 Connie?

Post by bobbystone » Sat Mar 24, 2012 5:15 pm

Delving into some fuel line problems I've been having. On reading up I read about anti-siphon valves. Should my 58 38' Connie have these? Does it?

I want to extract the fuel pickup tube to see if the screen is clogged. What precautions do I need to take to prevent explosions / fire?

I have a feeling I'm getting weak pressure / volume. What's a good way to test for this? The Genny and stud engine are on the same tank/fuel line and both suffer from fuel starvation symptoms.

Thanks All!
1958 48' Constellation
Twin 454's with Paragon Transmissions
Hull No. : X-48-107

Peter M Jardine
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Post by Peter M Jardine » Sat Mar 24, 2012 6:00 pm

No, you probably don't have an anti siphon valve on either engine. Yes, putting one on the generator side is an okay idea... You could have a plug in the pickup, but it's fairly rare, usually a result of very old gas sitting at a low level in the tank.

BUT... if you have low fuel pressure or starvation you could have a couple of issues. If one or the other appliance had low fuel pressure, I could say it was a fuel pump. With both of them exhibiting the same symptom, I would say it is the fuel system.

If both are hard starting, or start and stop when cold, but seem to get better when warmed up, then you have an overall lack of fuel. My first suspicion is your water fuel separator if you have one. The filter may be clogged, some water in it.

The second one is really important: You might be sucking air somewhere, and that means you have a breach in your fuel line integrity. It could be at the connections to the fuel pump, water separator, tank, generator...so taking those fittings off and putting a small coating of pipe dope (the type used for natural gas and propane lines) on the fittings then tightening everything up would be the first step. If you have copper lines still installed from your tanks, keep in mind that current ABYC standards no longer endorse solid fuel lines. They can develop very fine cracks or fractures from age and vibration. One of the answers here is to run new fuel lines in UL approved rubber fuel line, and see if the problem goes away, if the fitting issue did not solve the problem. Frankly, if your copper fuel lines are original, they are long overdue for replacement. Do not dawdle with this stuff...it is one of the most dangerous issues you could face on an inboard gasoline powered boat.

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bobbystone
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Thanks Peter

Post by bobbystone » Sun Mar 25, 2012 12:24 pm

Thanks Peter for your excellent and helpful reply. I've long been suspicious of some sort of air ingestion into the lines. If I try to run the engine past 2000 RPMs it will run for a bit and then starve out until I pull the throttle back down, when it will kind of catch back up again at a lower RPM. After reading a post on a fellows boat exploding I think it's probably a great idea to go ahead and replace the fuel lines. I'll create another post on that topic.
1958 48' Constellation
Twin 454's with Paragon Transmissions
Hull No. : X-48-107

Peter M Jardine
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Post by Peter M Jardine » Sun Mar 25, 2012 6:09 pm

No problem, happy to help... let us know how it works out.

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Post by Wood Commander » Sun Mar 25, 2012 6:14 pm

Your ant-siphon orifice is found in the threaded fitting where your fuel pickup tube goes down in the gas tank. It looks a little bit like a Holley carburetor main jet and is just under the threads of the pickup fitting if my memory is not failing me. And yes, you need it and you need it to not be clogged. This will prevent a bad fuel pump diaghram from filling your bilge full of gas.

Also, check your fuel tank vents on the side of the hull. Insects can get up in there and build webs and nests and stuff and clog the vent line.

And pertaining to the other fuel tank post, you should be OK concerning grounding as long as you keep your nozzle tightly against the fill pipe as you fill the tank. The friction of the fuel passing along the fill pipe can cause static electricity to build up and not letting the nozzle bang around will prevent this static buildup from arcing. To be really safe you could make up a piece of 1/8" flexible metal cable and attach battery charger-style alligator clamps to both ends to temporarily clamp the cable on from the fill pipe to ground, or maybe water, as you fueled. This is how they do it when fueling aircraft.


The factory used a rubber hose section between the upper deck fill pipe and the pipe nipple sticking up out of the tank.
But the engineers were pretty clever and took a piece of flat copper and ran it along the outside of rubber hose section and bent it's ends over so that they wrapped around into the inside of the hose. These ends were trapped between the rubber hose and the pipe nipple sections when the fill pipe and hose was installed and fastened down with hose clamps, thus keeping electrical continuity between the upper fill pipe and the tank and still giving a flexible rubber section between the two for alignment tolerance and vibration dampening.
Bret

1953 35' Commander "Adonis III"

1970 23' lancer project

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bobbystone
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Is this it?

Post by bobbystone » Sun Mar 25, 2012 6:25 pm

Thanks for the reply. I'm attaching a picture. Is this the anti-siphon device that the cut off valve is attached too? If so, from which end would I clean it?
Image
1958 48' Constellation
Twin 454's with Paragon Transmissions
Hull No. : X-48-107

Peter M Jardine
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Post by Peter M Jardine » Sun Mar 25, 2012 6:54 pm

I should have clarified my post... You don't have an anti siphon going the other way... So the fuel line will siphon back and create a void that the fuel pumpwill have to fill back up. An antisiphon on the tank is used to avoid siphoning if the diaphraphm goes, or if the carburetor is lower than the fuel tank level as stated. Most of the simple ones are a ball bearing an a spring.. The pump can over come it but gravity can't.

Yes indeedy, those old fittings need an overhaul.

I see white 'teflon' tape on those fittings too... a BIG no no. Most modern teflon tapes (china) have little teflon in them, and are not resistant to fuel. Use this stuff if you want the real deal.

http://www.gsasupplyco.com/gaethse.html

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Post by quitchabitchin » Sun Mar 25, 2012 9:18 pm

We fought this exact same issue, minus the gas in the oil, for two years. Actually had several issues.

1. Metering rods in the carb were broken, therfore lodging in the jets and slowing fuel flow at higher rpms. Rebuilt carb, helped tremendously.

2. Fuel tank needed cleaned, lots of debris was clogging pick up tube, filter, etc. Had tank cleaned. No more debris.

3. Fuel pump was actually cracked at the fuel inlet. Cast aluminum housing must have cracked from overtightening, copper flare lines had to be very tight to keep from leaking. This was likened to drinking water through a straw with a hole in it, you get some water but not all of it. Got a new pump and switched to flex lines.


Could be a number of things, start with the easy ones and eliminate one at a time.
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Wood Commander
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Post by Wood Commander » Sun Mar 25, 2012 9:58 pm

The anti-siphon is just inside the tank. See the brass hex nut shape right on top of the tank where the horizontal line (with the non-original shut off valve) is running in to it? Take the horizontal line off, and take the hex nut fitting out of the tank. The pickup tube is part of the hex nut fitting and runs down into the tank. You'll be pulling the whole tube up and out of the tank when you pull the hex nut out. Just under the hex nut fitting's threads is where you should find the anti-siphon orifice.
Bret

1953 35' Commander "Adonis III"

1970 23' lancer project

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bobbystone
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Thanks to everybody

Post by bobbystone » Sun Mar 25, 2012 10:27 pm

Thanks to everyone with your excellent replies. What a vast wealth of knowledge and wisdom this forum is. Makes you wonder how people managed to have "eccentric" hobbies before the internet!
1958 48' Constellation
Twin 454's with Paragon Transmissions
Hull No. : X-48-107

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