Vapour Lock

[Old Ironmaker]

I know where to get good answers for a problem. So here I am. At the end of last season I went to fill my tank for winterizing.

 

My fuel gauge has always had a problem which is it always shows full until about a quarter. Although the gauge showed full based on useage I know it was 1/2. I filled the tank and after about 20 liters it suddenly overflowed from the filler port, nothing came out the vent cap. I know it was nowhere near full even though the fuel could be seen at the top of the filler tube.

 

I took the boat home and removed the vent and fished a long wire down the filler tube but didn't feel any resistance and the fuel couldn't be seen any longer before fishing the wire. Replaced the vent cap and filled again, slowly. I could here the fuel rising and it took another 20 liters.

 

Went for a ride with the boat in tow to the next gas station before filling looked down the tube and couldn't see any liquid and it took another 20 or so litters.

 

Continued the tour of filling stations in the county and the last stop the fuel level was at the top, tank full.

 

It's doing the same thing this season. I hoped the problem might magically disappear, no such luck.

 

I'm told I have a vapour lock. Is it vapour lock? Those persons aren't able to give me a fix. Changing the float is on my to do list. It actually has made me more aware to fill constantly. Ran out once, that's enough.

 

Any suggestions folks. Thinking just now would filling with the vent cap off tell me anything?

 

Thanks in advance,

 

JD

Edited July 8, 2014 by Old Ironmaker

[Old Ironmaker]

I've learned more about fuel venting in the last few hours that I ever thought I would need to know. Vapour lock has nothing to do with filling a gas tank. From what I have learned vapour lock is a phenomenon referring to fuel starvation while the engine is running, so lets forget vapor lock.

 

The vent cap on the side of the boat, Starcraft 190, is both the vent to allow air into the tank in order for fuel to flow may or not be an anti surge line as well.

 

My filler cap which is manufactured by Perco does not have a vent feature on it. It is a solid plastic fitting that screws into the filler cap.

 

There is a screen on the inside of the cap on the vent, this to ensure critters don't plug the line, it's clean. I'll check again when the sun's out.

 

A common cause is dried scunge on the inside of the vent line caused by fuel splashing up and into the line when riding in rough water. Suggestion is to blow only this line out with air. I don't want to do that, the scunge or crud caused by phase separation will then go into the tank, then where will it end up? Probably somewhere I don't want it to be when I'm 15 miles out in the shipping lanes in Erie. I could always carry a spare fuel filter, which I do, but if anyone thinks I'm going to be able to change it while bouncing around in 1 meter waves they have a very high opinion of my mechanical abilities. It's a pain to change while the boat is on the trailer.

 

I don't know if this line has a kink in it, or has got a loop somehow that will create a seal somehow. How can I check for that?

 

Also I should add, that filler cap becomes very, very tight somehow between fills. I don't know why.

 

Hope my homework helps.

Edited July 8, 2014 by Old Ironmaker

[bigbuck]

If possible, take off the vent line and blow it out or just replace it. Fuel tanks need to vent to operate properly and it sounds like your's is not. Good luck gettin r done and get back out on the water.

[Garnet]

Think you have a spider wed in your vent hose. No amount of air will take it out. I would replace.

Edited July 9, 2014 by Garnet

[Old Ironmaker]

Thanks, this tank is buried in the floor same as the vent, if I could easily change the line I would. If I need to rip the boat apart to replace a vent line plugged it will stay and full the tank will be everytime I put it back on the trailer.

 

Thanks

[Musky or Specks]

You know, we had a lot of fun tonight. But, there' s nothing funny about... vapour lock. Its the third most common cause of stalling. So please, take care of your car and get it checked. I'm Joe Namath. Good night!

[Entropy]

Does it make a difference if you try to fill it when the bow is significantly higher than the stern, and vice-versa?

 

My old boat and my friends boat both will take more gas depending on boat 'levelness'. In both situations you end up with the tank that is empty higher than the fill and vent tubes.

 

Try filling it with the bow cranked up on the trailer, and the bow right down on the trailer. I'm willing to bet one will work for you, unless I have totally misunderstood this case.

 

Entropy

[DanD]

I understand your concern about blowing air down the vent tube and the dirt.

Why not try blowing air into the fill tube; you'll likely get some gas out the tube but it may also blow the restriction out if there's one?

 

Dan

[Old Ironmaker]

You know, we had a lot of fun tonight. But, there' s nothing funny about... vapour lock. Its the third most common cause of stalling. So please, take care of your car and get it checked. I'm Joe Namath. Good night!

I understand your concern about blowing air down the vent tube and the dirt.

Why not try blowing air into the fill tube; you'll likely get some gas out the tube but it may also blow the restriction out if there's one?

 

Dan

Hey Joe, remember that night at the 747 Club at the Buffalo airport after a Monday night game? You still owe me a hundred bucks.

 

Dan I was thinking about doing that and was told b a marine mechanic It can't hurt. He isn't as concerned as I am with stuff getting into the tank. He said you would be surprised at the crap at the bottom of all gas tanks. And that's what a fuel filter is for.

 

Enthropy. The bow is always much higher then the tank on the trailer, I could disconnect the tongue and crank it up if nothing else works. I don't know the science of that, yet. By the way I've always favored your 1st law over the 2nd.

 

Thanks all

JD