Fuel tank / line issues part 2

[cpoint]

Qr Bbpost

Qr Bbpost And why would air not go in constantly when I blow air in. Is the tank pressurized, is the pressure relief valve out side blocked? how to I clear that if so? Or I am thinking there is something that is in the intake valve that's not letting air back because it's blocked? Only way to see that is to obviously remove intake line. Any one done that, or anyone knows the part that I would need for 2000 carver 356 intake valve? I figure if I remove, mine as well put new one in?

The tanks are not pressurized as they are vented to atmosphere, assuming your tank vents are clear and not restricted.

Actually on the surface it seems like those anti-siphon valves are working but they should still be checked for debris and operation......basically just a one way valve depending on the maker....allows fuel out of the tank when there is suction on the engine side ( engine fuel pump running ), but if the line breaks or there is a leak with no suction the valve does not allow the fuel create a siphoning action and drain out to the bilge.

bud, not sure that's the case. because I was able to blow air through the hose all the way from engine side to tank without effort. so I though maybe I did not have anti-siphon valve. But then after first try I was not able to anymore. So definetly there is some issue with that valve. It must have been open position and i manage to blow air through it till it sat back down. than I was not able to after 2nd or 3rd try. So tomorrow I plan on removing the valve and check. I like to get a new one while I am on it, does anyone here know the part for 2000 carver 356 anti-siphon valve? n If I can't figure out, basically I will remove it tomorrow and check at west marine, hope they will have same. I am assuming these are standard part, sut the right size needed.

[cpoint]

sorry post was posted twice and do not see delete function.

[cpoint]

Qr Bbpost You have more than 1 tank to pull fuel from, are you having issues pulling from either tank? The only common fuel line is from the fuel selector valves to the engine. Anothr option You could temporarily swap fuel lines from the genset pickup as long as your tanks at least 1/2 fuel since its shorter and try that Where did the mechanic hook up the external tank?

he bypassed all lines, direct from his portable to engine before filter. starboard and aux is fine, definitely pickup line and/or anti-siphon valve.

[cpoint]

Well it was a good day, took some effort, but managed to remove the anti-siphon valve. The hose nipple was not so easily removable, so I left it be. Than I cleaned it up, did get some stuff out of it, I think was causing it to be left open position. Since I was not able to get a new one, can't seem to fin one anywhere at local marine shops or online, I placed it back on the tank. Started up the engine, amazingly started with no issues. was too windy to do test ride, but ran it at dock for 10-15 minutes, revved up to 3k. Did not stall or go crazy with tach display. so keeping fingers crossed it is good to go. Meantime I would be grateful if you guys have any idea where I can get one of these to keep handy. Attached is the part I have, keep in mind this is the anti-siphon valve and hose nipple attachment, since I was not able to separate them.

[Viper]

There are several on Amazon but should be a common inventory item at marine retailers. The newer ones tend to be one piece having both the pipe thread and hose nipple in one fitting. If the thread is 3/4" dia you are looking for 1/2" male NPT (MPT). I would double check the hose ID (inside diameter). It should be indicated on the hose.

[cpoint]

Hi guys, with a new grand daughter and other things not doing much boating since last year, so every other week I am trying something out to resolve this fuel flow issue. So just to recap what's been done and where I am now, and see if you guys can give some ideas.
1) Mechanic had checked everything (he is very good, and I trust him 100%), and came to conclusion engine and fuel injectors had no issues.
2) He plugged in his own gas tank direct to engine side, all was running perfect
3) conclusion between tank and engine there is some restriction, so once I go over 2K RPM, RPM gauge goes wacky, and if I continue engine will die, restarting and staying below or at 2K, it's all good.
4) took out anti siphon valve, cleaned up and put it back, tested same issue continued
5) replaced the 6port switch, same issue continued
6) I blew compress air back through the pickup line into tank, same issue continued
7) switched to AUX tank, same issue continued

So I am going to do the following;
1) hose from switch to engine was replaced few year ago from west marine, don't expect a problem, but will remove and visually check inside
2) Replace the fuel filter again
3) I am planning on cutting floor and taking out the pickup line, which may have some issue, based on other who commented on that
4) I like to replace the anti-siphon valve, but I can not find one that's on there 3/4 threaded on both sides. Checked online, checked parts stores pf various marine parts stores, can't find it. If anyone knows where I can find one please let me know here.
5) Fingers crossed, above resolves the issues

[bud37]

I would replace all the hose from the tank to the engine with new.....it is possible the hose has been stepped on/kinked in some manner and inside it fails closed under suction. I don't believe blowing air thru will tell anything if that is the case. That style of hose may do that and hose is fairly cheap and good to cross off the list for sure ( erase any doubt).

Be sure to get the correct coded fuel hose in your size.....good luck.

[km1125]

Qr Bbpost

Qr Bbpost You have more than 1 tank to pull fuel from, are you having issues pulling from either tank? The only common fuel line is from the fuel selector valves to the engine. Anothr option You could temporarily swap fuel lines from the genset pickup as long as your tanks at least 1/2 fuel since its shorter and try that Where did the mechanic hook up the external tank?

I think genset line has same issue, which I am going to check once I start working on the port side one. That has not pulled fuel from port tank in 2-3 years, never had a need for. But pretty sure the anti-siphon valve on that is bad.

In this post are you saying the generator also has a problem pulling from the port tank?

In your pic earlier it looks like there's another fitting between the engine and the generator feeds. Is that an unused fuel pickup? If so, can't you just move the port engine feed to that fitting?

Also check/verify if these were made by Florida Marine Tank. They did have "dip tube" replacements for a series of tanks around your years. You might want to find the tank info on the label on the tank and call them to see if they still offer those replacements. IIRC the originals were copper or copper clad and the replacements are some type of plastic.

[cpoint]

Thanks, I will replace hoses. I'll check with Florida Marine Tank also, not sure what mine was, there is no label on it or documentation to my knowledge. I am thinking at this point it could be the dip tube or pickup line. Also since I can not find anti siphon valve that is compatible, I was thinking about temporarily removing it go direct hose to tank with brass fitting to see it is the anti siphon valve. as you can see from picture it is pretty old. It seems to be working, but not at higher RPM maybe? you think it is OK to run without anti-siphon valve to test out in the harbor?

[km1125]

Yes, you can remove it for troubleshooting, BUT MAKE SURE YOU REPLACE IT. Murphy's Law says you're much more likely to actually HAVE a problem if you remove something like this!!


Your tank ABSOLUTELY has a label on it. That's a REQUIRED item by the USCG for a manufacturer. It might be hard to find, but I've always been able to find them. You might even take some pictures in areas that are too hard to get your head into... just stick the phone in there with a flash on auto and take some pics. The tank WILL have a serial number and a manufacturer ID on it (along with other info).

What about that other fitting? Is it usable?

Your boat is not that unique and really not that old. The one I just sold was almost 20 years older and I could still get all the parts I needed. You just need to know the right size and the screwy way that pipe and hose is measured and designated. A 3/8" NPT is really almost 3/4" in diameter. You need to check/verify the hose size. Most boats your size would probably use 3/8" fuel hose, which is the inside diameter of the hose. The hose barb will be a little larger to provide a tight fit, so it might LOOK LIKE it's 1/2", but check the hose because THAT is where the spec is. As viper said, look on the actual hose for the correct size.

Here are a couple different valves that might fit.
https://marinepartssource.com/anti-siph ... -180-b-1-2

https://marinepartssource.com/anti-siph ... -l-170-1-2