Still unsolved vent issue

[boomer2]

95 model 50hp J50TLEOD Johnson. Fuel tank is OMC Dura-Tank non-venting cap..it appears to be the cap that came with the tank according to BRP parts diagram. This tank is under deck (but portable). Problem is that a lot of pressure is building up causing leakage around the fuel hose connection area. Went to local johnnyrude dealer and the cap he had looked identical to the one I had...non vented. I called the technical assistance number on BRP website, the guy said the system had to be vented either an auto vent system or a vented cap but couldn't advise me to which system my engine had. Common sense tells me that this being an underdeck tank it should not have a vented cap in an enclosed area for obvious reasons.. which leaves the auto vent system. The BRP tech did say an auto vent vented to the crankcase somehow and couldn't tell me more. How can I find out how a auto vent system works and why (if I have one) it isn't working. Sorry for being long-winded...I'm not the best at explaining things I suppose. I'm at a wall with this thing. Even Googled "outboard auto vent" and didn't find anything specific or actually helpful. TIA.

 

[Daviet]

Re: Still unsolved vent issue

Doesn't your tank have an external vent going to the outside of the boat so that you can fill your tank without it blowing fuel back at you?

 

[boomer2]

Re: Still unsolved vent issue

Doesn't your tank have an external vent going to the outside of the boat so that you can fill your tank without it blowing fuel back at you?

No. It's a 6 gallon portable tank that go's under deck. It's accessible by opening a hatch lid and lifting out the tank.

 

[Daviet]

Re: Still unsolved vent issue

I thought all 6 gallon tanks used a vented tank cap so that the primer bulb would not suck flat.

 

[boomer2]

Re: Still unsolved vent issue

I thought all 6 gallon tanks used a vented tank cap so that the primer bulb would not suck flat.

This is what I'm concerned about. The vent system must be the "auto vent" style the BRP tech touched on. It somehow must vent around the carb area or into the crankcase somehow but after looking at countless parts diagrams I don't see anything that would pertain to a vent. Looks to me like a system like that would need two lines from the tank instead of one...

 

[Daviet]

Re: Still unsolved vent issue

What type of problem are you having with your motor?

 

[TLL]

Re: Still unsolved vent issue

On your tank, when you plug in the fuel lineconnector to the tank, the connector also pushes in a pin that opens the vent for the tank. It allows air into the tank, but not out. That's why the tank becomes a baloon when hot. If you have fuel leaking out by the connector, you need to replace the connector as it is not sealing well onto the tank. To test this, remove the fuel line connector from the tank, if the leak stops, the fuel line connector is bad. If the leak continues, the tank adaptor is bad.
There is no vent on the gas cap.

 

[boomer2]

Re: Still unsolved vent issue

What type of problem are you having with your motor?

RPM's only going to 3500, tach could be off and that doesn't concern me too bad for now. The problem is the tank building up pressure to the point it's pushing fuel out the connection fittings and gasket area. In an enclosed area with bilge and aeretor pumps not to mention batteries this has potential for igniting or explosion.... and it could *possibly* be connected to the RPM issue.

 

[F_R]

Re: Still unsolved vent issue

Not familiar with that one, but typical OMC/BRP tanks have a passive vent that is vented only one way. It will let air into the tank but not allow air/fuel to slosh back out--for obvious safety reasons. I think you will find it is built into the fuel outlet housing and requires no action on your part. That is why it is called auto vent.

 

[boomer2]

Re: Still unsolved vent issue

On your tank, when you plug in the fuel lineconnector to the tank, the connector also pushes in a pin that opens the vent for the tank. It allows air into the tank, but not out. That's why the tank becomes a baloon when hot. If you have fuel leaking out by the connector, you need to replace the connector as it is not sealing well onto the tank. To test this, remove the fuel line connector from the tank, if the leak stops, the fuel line connector is bad. If the leak continues, the tank adaptor is bad.
There is no vent on the gas cap.

I figured it must not use a vented cap the tank being enclosed as it is. I do have another tank connection on order and it wasn't easy to find...dis-continued. It's almost square shaped, about 2"x3" that has 4 bolts holding it to the tank. The unit also has a fuel gauge on it. I don't at all like the idea of a under deck plastic gas tank that baloons. Bad design in my opinon, there had to be a better way such as a permanent tank and external vent. I'd still be curious to learn about the "auto vent" system the BRP tech mentioned.

 

[boomer2]

Re: Still unsolved vent issue

Not familiar with that one, but typical OMC/BRP tanks have a passive vent that is vented only one way. It will let air into the tank but not allow air/fuel to slosh back out--for obvious safety reasons. I think you will find it is built into the fuel outlet housing and requires no action on your part. That is why it is called auto vent.

Still seems like a odd way to design something doesn't it. If you have to go to the trouble of designing a special tank connection that basically vents into the atmoshere why not just put a standard 90* elbow on the tank and use a vented cap? The purpose of keeping gas fumes out of an enclosed under deck area is not accomplished..the boat does however have the vent's on the rear top of the hull, one faces semi-backwards and one faces semi-forward so maybe the danger's don't exist as bad as I thought. Proper vented seems a fuel system would not baloon any.

 

[boomer2]

Re: Still unsolved vent issue

Thanks all.

 

[F_R]

Re: Still unsolved vent issue

Still seems like a odd way to design something doesn't it. If you have to go to the trouble of designing a special tank connection that basically vents into the atmoshere why not just put a standard 90* elbow on the tank and use a vented cap? The purpose of keeping gas fumes out of an enclosed under deck area is not accomplished..the boat does however have the vent's on the rear top of the hull, one faces semi-backwards and one faces semi-forward so maybe the danger's don't exist as bad as I thought. Proper vented seems a fuel system would not baloon any.

You seem to indicate that maybe the area is legally vented. As you would imagine, it is illegal and dangerous to put portable / unvented tanks in an unvented enclosure. Perhaps you might consider a properly installed and vented permanent tank.

I can tell you that I carry two portable tanks in my boat. One has a vented cap and one has the automatic pin-pusher vent. They both slop gas out. One out the vented cap, and one out the needs-repair automatic vent. If they weren't in wide-open spaces, I would do something about it. Should anyway, shouldn't I?

 

[boomer2]

Re: Still unsolved vent issue

You seem to indicate that maybe the area is legally vented. As you would imagine, it is illegal and dangerous to put portable / unvented tanks in an unvented enclosure. Perhaps you might consider a properly installed and vented permanent tank.

I can tell you that I carry two portable tanks in my boat. One has a vented cap and one has the automatic pin-pusher vent. They both slop gas out. One out the vented cap, and one out the needs-repair automatic vent. If they weren't in wide-open spaces, I would do something about it. Should anyway, shouldn't I?

I'm sure they are legal due to the vent/air intakes. I wouldn't worry about wide open spaces too bad but an enclosed area full of raw gasoline and fumes gets my attention..especially if I need to flip a pump on. Does the "pin vent" you mentioned have a very small diameter pin in the center of the left side fuel prong? I am assuming the right prong is just a support for the connection?

 

[F_R]

Re: Still unsolved vent issue

I'm sure they are legal due to the vent/air intakes. I wouldn't worry about wide open spaces too bad but an enclosed area full of raw gasoline and fumes gets my attention..especially if I need to flip a pump on. Does the "pin vent" you mentioned have a very small diameter pin in the center of the left side fuel prong? I am assuming the right prong is just a support for the connection?

As I indicated up front, I'm not familiar with your particular tank, but here is the older one that is very common. On this one, #23 are two pins that are pushed in when the fuel line is connected. One of them opens/closes the fuel flow. The other one opens/closes the vent. But the vent is not a free-flow thing. Instead it is limited to flow in one direction only by the one-way valve parts, items 26, 27, and 17.

I don't know how well this compares to what you have.

 

[boomer2]

Re: Still unsolved vent issue

As I indicated up front, I'm not familiar with your particular tank, but here is the older one that is very common. On this one, #23 are two pins that are pushed in when the fuel line is connected. One of them opens/closes the fuel flow. The other one opens/closes the vent. But the vent is not a free-flow thing. Instead it is limited to flow in one direction only by the one-way valve parts, items 26, 27, and 17.

I don't know how well this compares to what you have.

That appears to be it FR. Hard to tell 100% though. When the new fitting arrives I will tear into the old one and compare what I find to the diagram. Thank you for that.