2100v fuel delivery problem.. HELP !!!

[TeamAllen]

Where is the anti-siphon valve generally located?

[jciscott]

The anti-siphon valve is right on the outlet of the tank. I took the floor out to install the new fuel sending unit ( which is working great....) The anti-siphon looks like nothing little fitting. It is an aluminum fitting, 1/2" male pipe thread to 3/8" barbed hose, that thread into the brass 90deg fitting that threads into the tank. My BIG problem came when I tried to take the anti-siphon out to try to clean it, and it twisted off in the brass 90, which statred my frantic, and fruit-less search for a new replacement. I am in the industrial controls business, and have very good sources for this kind of thing, and all my sources agree that the tank manufacturer must have custom fabricated the thing. Tige gave me a contact at the tank manufacturer. I tried the tank company in Flordia, the guy I needed to talk to was on vacation for 2 weeks and no one else had any idea what I was talking about......
Thats when I went to my machine shop friends house to drill and tap the broke off alluminum fitting, and I bought a simple straight through brass fitting .......

[teachercop]

The technique I recently learned seems adequate. The anti-siphon is on the fuel tank outlet. On the DD, I only had to take a corner section off that covers the vent. Easy access, I was going to search for a replacement valve, I am thinking maybe not after your pursuit.

We did not separate the brass fitting and the valve,,,took it right off the tank and performed the repair.

Did the new sender improve gas gauge readings?

[jciscott]

The sending unit was cheap, quick and easy....
I got the generic model at the local marina, about $25 bucks.... DIM also has the same thing.
The instructions have you cut the rail to a length something like 1" shorter than the tank depthm and the to cut the float arm to a length based on the tank depth.
The guage reads full when full and about 1/2 when it should be at 1/4 but it is linear, stable and repeatable.

It is the little things.......

[R&T Babich]

Does anyone know what is the purpose of an anti-siphon valve for our fuel tanks? I've never heard of anything like that before.

I added a fuel flow gauge to our boat and a second fuel/water seperator filter between the sensor and the fuel tank. I also added a spare marine electric fuel pump to the original filter and can now use the pump to prime both filters or pump gas out of the boat if I need to drain the tank or someone needs gas. When I was priming the filters I could hear a weird suction/surging noise from near the fuel tank outlet. Must have been the anti-siphon valve.

[loudelectronics]

Are you guys having these problems with carbed motors or EFI? I am having similar issues with a 6.0 vortec. Happens about once every ten hours then dissapears like nothing is wrong.

[chpthril]

Are you guys having these problems with carbed motors or EFI? I am having similar issues with a 6.0 vortec. Happens about once every ten hours then dissapears like nothing is wrong.

Since you have a 6.0, my first thought would be vapor lock. There have been some others on here experience this. Check with (username) FIC, he can probably give you some insight on this.

[TeamAllen]

Does anyone know what is the purpose of an anti-siphon valve for our fuel tanks? I've never heard of anything like that before.

My understanding is it is a valve that keeps fuel from siphoning out of the tank when the motor is not running. When the engine is running it creates vacuum or pressure and opens the valve to allow fuel to flow. You only need one (by law) when your fuel tank is higher than your carburetor. It seems like a good/safe idea to have one regardless. What if a hose lower than the carb started leaking?

When I did a search to learn more about it I found this link to the law.

http://www.uscgboating.org/safety/bo...el/183-568.htm

So the valve is not a Mercruiser part? I will have to locate one some where else?

[chpthril]

My understanding is it is a valve that keeps fuel from siphoning out of the tank when the motor is not running. When the engine is running it creates vacuum or pressure and opens the valve to allow fuel to flow. You only need one (by law) when your fuel tank is higher than your carburetor. It seems like a good/safe idea to have one regardless. What if a hose lower than the carb started leaking?

When I did a search to learn more about it I found this link to the law.

http://www.uscgboating.org/safety/bo...el/183-568.htm

So the valve is not a Mercruiser part? I will have to locate one some where else?

Great find TeamAllen, thanks for the link.

[jciscott]

TeamAllen..
I agree...good find... although the antisiphon appears to be redundant as the the tank is the lowest part of the boat... all the fuel runs up hill to the fuel filter, fuel pump, etc....
To LOUDELECTONICS... my motor is a 5.7 EFI 315HP, in my 1999 2100V.

Here is a link to buy the thing.....
http://www.marineengine.com/products...php?in=3470478

Also... side note.... has everyone discovered MARINE HARDWARE as the source for all inboard stuff like shafts,struts, stuffing....?? This is where I got my new strut... at about 1/2 what Tige wanted to sell it to me.... Marine Hardware makes all the running gear for EVERYONE.... check it out.....
www.marinehardware.com

[da.bell]

TeamAllen..
I agree...good find... although the antisiphon appears to be redundant as the the tank is the lowest part of the boat... all the fuel runs up hill to the fuel filter, fuel pump, etc....

While on dry land it certainly is but when the boat is in the water and/or the TAPS plate is down, the moter will certainly be lower than the fuel tank.

[TeamAllen]

Thanks jciscott!

Those links are very helpful. I have never heard of that site before. I put it in my bookmarks. I had the idea before to have a links section on this site, but no one else seemed to agree. Everyone is always asking where to get this or that.

I'm still not sure where exactly this part is located. On top, side or bottom of the fuel tank. I think my fuel tank could be close to engine height. I've never really thought to much about it. I bet when I trailer the boat down hill, like a steep launch ramp the stern is higher than my engine. Yours is a V drive, mine a direct drive. There is a big difference right there.

[jciscott]

My fuel tank is under the floor in the very center of the boat. To access it, I had to remove the center section of the floor, a 48" * 18* carpeted board.
The tank outlet is on the top of the tank, in the rear corner.
The floor was kinda saggy in the front, I found this to be the screws were rusted off on a piece of wood that the floor sat on. New stainless nuts and bolts cleaned this right up.......

[teachercop]

Well, my problem re-occurred. After a few hours of boarding up here at Powell, we shut down to swim and eat. When we resumed, the 'vapor lock' like condition presented itself. I have a anti-vapor lock tool. I grabbed my sons souble barrel water squirt blaster gun, suck up some ice chest water from melted ice, remove the fuel pump/fuel cooler cover, blast it with the cold water, problem gone.

I think I am going to roll with this technique for the remainder of the trip.

I will be replacing the pump this fall/winter after I shop the price.

[TeamAllen]

Our problem happened after sitting for awhile also. The only way I got mine to run again was by pumping the throttle rapidly until it blew out what ever the problem was. I figured now it was this anti siphon valve and I was just overcoming the pressure needed to release the anti siphon valve. The only other consistent thing, I noticed, was the fuel pump would make a high pitch squeal noise for a few seconds after it restarted. I still would be surprised it is the fuel pump, since it is like an all or nothing thing.

Teachercop - Did the mechanic just free up your existing anti siphon valve? Or did he replace it with a new one?