Gasoline smell outside/under Class C

[arcFlash]

Hello everyone,
Just returned from a 5 day trip to Arkansas (from Minnesota). Day one of the trip I could smell gasoline outside when standing behind or near the back. It's an 02 Winnebago 29B with a lot more rust from salt than I'd like.... So I crawled under for an immediate inspection. No leak detected but it's clear the top of the gas tank is venting. The tank pressurizes as expected or always has when it's hot outside and I've been driving. I don't get a smell in the morning when it's cool outside and everything is cold soaked. I suspect there may be some vent that isn't closing when the tank gets hot and releases pressure it fails to reseal.

I'm going to hunt it down and report what it was when I find the cause but if anyone knows a likely cause or advice I'll take it.

 

[donn]

Rotten rubber gas line would be my first guess

 

[arcFlash]

Fuel pump is in the tank so all fuel lines are pressurize to injector pressure and I don't have any signs of a leak and both Genni and Engine perform normally.

When I replaced the fuel filter last year I elected to not depressurize the fuel rail (mistake) and it released a considerable amount of fuel spray so a fuel line is unlikely but can't be ruled out.

 

[Lou Schneider]

The generator fuel line isn't pressurized so it could be seeping only when the tank builds up pressure.  Most likely at the rubber jumper between the tubing running along the chassis and the outlet at the top of the tank.

 

[cgmartin]

Does your motorhome have the famous charcoal canister? In most vehicles, it is located behind the gas tank, or next to it, mostly on the driver's side. Its purpose is to route gas vapors from the tank back to the engine, to prevent them from being released to the  atmosphere. It could be possible that the valve that is attached to the canister failed and is releasing gas fumes. The canister also has at least two rubber hoses going to it. They also may have failed. Just another thing to look at.

 

[Alfa38User]

If the vehicle suffers from road salt damage, the top of the tank could also suffer from rust penetration. I lost count of the number of tanks I had to repair for this problem over the years and I am only a shade tree mechanic. Usually a good coat of epoxy did the job, at least temporarily, but it did mean dropping the tank to fix.

 

[arcFlash]

charcoal canister is a good idea but I've not seen it on my last expedition. Maybe it's on the road someplace. I bet that's the issue. I've had to weld broken muffler hangers so it's very likely the hanger for the can broke as well. Some electric glue and stick a new one in place.

tank rust:
My initial thought was a hole in the top of the tank from rust but it's since pressurized so I had to dismiss that.

 

[arcFlash]

Lou Schneider is the winner of the best guess at Generator fuel line. It started leaking when I bumped into it with my head. It was rotten clean through but.... the smell was the tank itself not the weak fuel line. I replace the rigid fuel line with normal fuel line and zip tied to the old line for support as I 'removed' about 6 feet for access reasons. I used a good quality hacksaw blade in a gloved hand and chopped the fuel line easily in a minute or two. Much easier then the stub mini-pipe cutter I tried to use.

Fuet Tank is rotten on the bottom under a hanger strap. It doesn't drip, it seeps out into a damp ring. When it hot out, it drys fast enough you can't see it but this morning when it was 39 degrees out, I could clearly see a 6 to 8 inch dark fuel stain that had a strong smell. Why was I under the camper when it was 39 degree? Fixing the genni fuel line and installing new shocks (14 years is probably time to replace, 3 of 4 were junk) as I was already set up to work on the chassis it was an extra 20 minutes to cut bolts and install new shocks in the rear.

Now searching for a fuel tank that isn't $1700.

Thanks everyone for the comments.