Aux. fuel tank not venting properly

[Finatic]

I'm hoping to get some advice on how to resolve a problem that I'm having with the auxillary fuel tank on my 232 Gulfstream. I purchased the boat in March and I'm still learning all the quirks. I recently discovered that the auxillary tank was not venting properly. I removed the gas cap I could hear the hissing noise caused from the pressure build up in the tank. Additionally, I have heard on 3 different occassions a burping sound coming from the aux tank while underway. I've spoken with Grady's customer service and they recommended that I check to make sure the vent line did not loop under the starboard side fishbox. Also, they stated that it could be pinched or simply too long. I pulled on the vent line and was able to cut off an additional 4-5" of slack. Also, I've disconnected the vent line and blew on the hose. My father was at the filler cap and said he could feel the air. Does anyone have any suggestions about what my next steps should be? I'm very leary about topping the auxillary tank off with the excesss pressure. Any advice would be greatly appreciated.

Derek

 

[BobP]

Taking out the 5 inches doesn't mean anything.

You are not supposed to top off fuel tanks, not even the one in your lawn mower.

If you do you will slosh fuel into the vent line at the tank nipple and the fuel will act in a way like a seal, not a good one though, otherwise the engine would have stalled by now on high vacuum.
If your vent is low in height relative to the vent nipple on tank, then more issues when fuel gets into the line since there will be more fuel to clear.

Did you follow the line all the way?

I'd suggest you thread a new fuel vent line (5/8 inch) following the old one with some duct tape end to end and replace it, perhaps one of the plys has parted and it's internally collapsed, not likely though, or ot's being crished or crimped along the route.

If your model has the vent built into the fill fitting, then you have to be careful not to get fuel into the vent while fueling.

My vents are on the side of the hull, I can hear them when fueling and even when I shut off the nozzle still hear them for a while. A lot of air has to be displaced - an equal volume to fuel entering.

My vent lines takes a dip before it goes into the tank as it rests on the hull, so there is a valley in it, some say this is no good, well if you believe the vent line has to be self draining.

It doesn't.

If fuel gets in my vent line it will be blown out of the vent when I fuel up, sometimes I just keep a cotton rag by the vent just in case when I first start filing. Will need a rag alos at teh fill ine when starting.

I used to have these problem when I would top off tank, but no more topping off, I use the fuel meter to monitor fuel usage and refill to the totalizer equal to fuel used. I made sure when I fist started I didn't have the tank topped off.

If the motor runs fine and squeeze bulb is not collapsing at high speeds and you can fuel tank ok, then there really isn't a problem.

 

[seasick]

I'm hoping to get some advice on how to resolve a problem that I'm having with the auxillary fuel tank on my 232 Gulfstream. I purchased the boat in March and I'm still learning all the quirks. I recently discovered that the auxillary tank was not venting properly. I removed the gas cap I could hear the hissing noise caused from the pressure build up in the tank. Additionally, I have heard on 3 different occassions a burping sound coming from the aux tank while underway. I've spoken with Grady's customer service and they recommended that I check to make sure the vent line did not loop under the starboard side fishbox. Also, they stated that it could be pinched or simply too long. I pulled on the vent line and was able to cut off an additional 4-5" of slack. Also, I've disconnected the vent line and blew on the hose. My father was at the filler cap and said he could feel the air. Does anyone have any suggestions about what my next steps should be? I'm very leary about topping the auxillary tank off with the excesss pressure. Any advice would be greatly appreciated.

Derek

The vent line should not have any spots where fuel would lay if it got into the hose. In other words, make sure that every section of the vent line if it had fuel in it would run back to the tank or to the filler cap. If there is a loop in the hose it has to be higher than the filler vent connection.
Assuming that you have the combo Perko filler cap, there is a rubber valve under the cap that has to move freely and there is a vent hole in the cap. If the hole gets plugged or the flap (looks like a round button shaped thing) sticks against the underside of the cap, the cap won't vent.

Hope this helps

 

[BobP]

Seasick, what you are writing is not consistent in how the boat is design/constructed. It may not be reasonable to achieve it.

The top of the tank vent nipple is only one or two inches below the deck level, the rest of the stringer grid height and foamed areas are well below that.

 

[seasick]

Seasick, what you are writing is not consistent in how the boat is design/constructed. It may not be reasonable to achieve it.

The top of the tank vent nipple is only one or two inches below the deck level, the rest of the stringer grid height and foamed areas are well below that.

If that is the case, there will always be issues with fule laying in the vent line. That said, there should be enough suction to clear the line assuming the low spot is not super low. I suspect that the vent line is blocked or the vented filler cap is plugged up. Running with the filler cap loose or off may help diagnose the problem. If the problem goes away, it is most likely a bad cap.