1997 355AC not able to pull from aux tank

[Saugatuck355AC]

Hello all, I have an issue of not being able to use the aux tank on my Carver. I have tried both engines on it and both stall out shortly after switching from their dedicated saddle tanks to the aux tank. The issue first arose on a longer trip this year. I was completely fueled up on all 3 tanks and running the aux tank for about 3 hours straight, no issues. We stopped and anchored for about 2 hours then continued on. About 30 minutes later both engines stalled and would not start until I switched to their respective saddle tanks. Since then I have not be able to run either engine off the the aux tank. Every time I try they stall after switching from saddle to aux. help is greatly appreciated!

[bud37]

Well there could be many reasons for this, lets cross off some possibilities first.

Are you sure there is fuel in the tank....you ran two engines off that tank for 3.5 hours, depending on what rpm that could be a lot of fuel gone. The natural answers are, the anti-syphon valve has become plugged or the tank vent could have become restricted, all things to check. Fuel gages are notoriously bad and the tank may not of got topped right up.

[bobkirkbride]

The anti-syphon valve is a likely culprit. It's normally closed but with engine running the fuel pressure opens it. I had that happen when it stuck closed. It's a $25 part.

[Midnightsun]

QR_BBPOST Well there could be many reasons for this, lets cross off some possibilities first.

Are you sure there is fuel in the tank....you ran two engines off that tank for 3.5 hours, depending on what rpm that could be a lot of fuel gone. The natural answers are, the anti-syphon valve has become plugged or the tank vent could have become restricted, all things to check. Fuel gages are notoriously bad and the tank may not of got topped right up.

I agree, maybe just no fuel left in that tank. Those mechanical gauge senders are notorious for being incorrect. A bad ground connection and it may show 1/2 a tank when in reality it is empty. Food for thought.

[buster53]

Agree...both engines for 3-1/2 hours? That's a lot of fuel burned. Have you added more to the tank?

[Saugatuck355AC]

Thank you all for the feedback. It has been accurate with the gage and it seemed I should have been about where I am on the gage based on previous usage so I’m 90% sure there is at least a quarter tank. The anti siphon valve is a great place to check next... where is it?

[buster53]

Almost positive the anti siphon valve is just inside the tank where the fuel line comes out of the tank. Believe me, it will not be easy to get to.
Before doing anything...check simple things first. Put 10 gallons of fuel in the tank. Just because the fuel gauge shows you have fuel, you may have a short fuel pickup in the tank.
Another easy check, after you put 10 gallons in the tank, leave the fuel fill cap off. That will tell you if you have a clogged vent.
After checking the easy things, then go after the more difficult. The anti siphon valve will be difficult.

[Viper]

From what I can remember, it's not that difficult to get to the top of the tank on a 355. I remember the top of the cabinet on the starboard side of the bed lifts off, and that the wall above the back of the bed comes off. The tank is behind there and the fuel connections are right there. The anti-siphon valve is the fitting on the outside top of the tank that your fuel hose is hooked up to. The sender is also there so I would test it to ensure it's working properly while you're there.

[buster53]

From what I can remember, it's not that difficult to get to the top of the tank on a 355. I remember the top of the cabinet on the starboard side of the bed lifts off, and that the wall above the back of the bed comes off. The tank is behind there and the fuel connections are right there. The anti-siphon valve is the fitting on the outside top of the tank that your fuel hose is hooked up to. The sender is also there so I would test it to ensure it's working properly while you're there.

Yes, you are right, on my 356 the top does come off, but the framing of the cabinet still blocks you from getting close. I had my tanks emptied last year (bad fuel problems) and my fuel guy could not get close enough to the aft tank to be able to work on it. The entire cabinet frame needs to be removed first.

[Saugatuck355AC]

Thank you all. I'll continue to see what I can figure out. I'll double check and drop some gas in it to make sure. I also like the idea of leaving the cap off to see that it isn't a vent problem. Really seems strange though that it just cutoff all of a sudden. Seems like a a sending unit could be the issue...