Leaking gas only when tank is full.

[Indy Itasca]

We have a 2005 Itasca on a 2004 Ford frame. If we fill the gas tank full we get a gas leak from somewhere up around the tank. Only last until the tank level goes down a bit. First time it happened I thought I might have over filled because I pumped more after the pump shut off. Since then it has happened twice and I have not over filled. I seldom run with a full tank anyway because I don't like the idea of using gas to haul gas, but I am not happy about this. 1. Is this a frame chassis issue or a coach issue? 2. It is a used coach with no warranty, what would be the best course to get it fixed? (I'm mildly mechanical but working around things that explode or catch fire, scare me.)
Thanks

[Indy Itasca]

We have a 2005 Itasca on a 2004 Ford frame. If we fill the gas tank full we get a gas leak from somewhere up around the tank. Only last until the tank level goes down a bit. First time it happened I thought I might have over filled because I pumped more after the pump shut off. Since then it has happened twice and I have not over filled. I seldom run with a full tank anyway because I don't like the idea of using gas to haul gas, but I am not happy about this. 1. Is this a frame chassis issue or a coach issue? 2. It is a used coach with no warranty, what would be the best course to get it fixed? (I'm mildly mechanical but working around things that explode or catch fire, scare me.)
Thanks

[BZam]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Indy Itasca:
We have a 2005 Itasca on a 2004 Ford frame. If we fill the gas tank full we get a gas leak from somewhere up around the tank. Only last until the tank level goes down a bit.
Thanks </div></BLOCKQUOTE>

There is probably a rubber material or sleeve from top of tank to your filler cap assembly. I had this happen and was able to just replace this sleeve.

But it is a material made just for fuel so need to go to good auto parts store to buy it. It was not hard to change other than being in tight place.

[Capt. Flipper]

Check the supply hose to your generator. It comes from top of tank and has been known to harden and split. Only leaks when tank is full. Whatever it is, you are probably looking at dropping the tank to find it

[rjf7g]

Hmmm...I had a leak in the filler tube of my 1992 E-350 based class C, but that leaked gas when filling up.

[tderonne]

A few thoughts.

The OEM Ford parts should NOT leak. They are darn near bulletproof. Having to pass evaporative emissions has driven all of the fuel line and tank components to be VERY durable. An '04 shouldn't have part wearing out and leaking.

That said, it's important to realize that lots of the stuff under your coach is not Ford OEM. The box builder adds the generator line, as was mentioned above, and another area that could be over looked is anything the box builder did when the either shortened or legthened your chassis (yes if happens). There's a piece of very corrored copper tube in one of my vapor lines, it isn't OEM, I guarantee it, and it's going to leak way sooner than the rest of my system.

Also, realize that you tank is never really FULL. If you do the math, you'll see that our tanks have nearly 100 gallons of total volume. So at "full", the liquid fuel level is only about 3/4 of the way to the top. There's about 25 gallons of vapor space. I had a fuel tank that would leak when fuel on a 1977 class C. It had no vapor space. There was a bad solder joint on the sending unit. When it was full it leaked. On our new tanks a leak like that would never happen. It might leak a little when driving, but I doubt you'd ever notice, and you would set EVAP codes once you finished an EVAP test. (doesn't happen that often. Takes a pretty long set of entry condidtions including the right soak (off) time.

And one last thing, are you sure it's from the tank? Behind the axle? Carbon cansisters can drip liquid fuel if a tank is over filled, getting liquid fuel where vapor belongs. But they are ahead of the axle, along the left frame rail.

[Jimary]

I have a 1999 Newmar and mine was leaking when full also. On mine it turned out to be the fuel filler hose. The neck on the fuel tank is VERY short, and the clamp was not on the hose straight. It took me a couple of tries because it is a very tight area, but I finally got the clamp on it straight and that fixed mine.

[tderonne]

Oh yeah, filler neck. That's another thing the box manufacturer does. Some do more than others. The "stock" filler is on the left of the tank. I've seen motorhomes with them on the right (they turn the whole tank around!), and out the rear (which must have some pretty long lines). Mine is what I assume to be all Ford parts, just out the left side. Where's yours?

On our '04's, the tank sits 2.4" lower than the earlier ones. I can sit just ahead of my tank and reach all the lines on the top. It isn't easy, but I wouldn't have to drop the tank to check things out on top.

[Indy Itasca]

Thanks for the replies!
Well, is my logic flaky here: If it was the fuel line that goes to the genset wouldn't it leak when the gen is running. I don't know much about it but always assumed there was some sort of fuel pump on the gen that pulled gas from the tank. If the rubber seal on that is bad wouldn't it leak gas anytime the gen runs?