The case of the disappearing gas leak

[Cougargm]

This story is a bit of a mystery. We were winterizing our 2005 Jayco Granite Ridge when I noticed a small puddle underneath the middle of the RV on the driver's side. There were two small drips coming from a bracket that were leaking gas. I can't tell what's above the brackets. I put a bucket underneath to catch the gas and had between pint and a quart the next morning. So I took it that morning to the garage and just like that- it stopped leaking. THe mechanics parked it on hills, drove it, ran the generator- and no leak. They put more gas in it, until the tank was full- and still no leak.
It seems weird that a leak would stop on its own, and the garage recreated various possible scenarios that might cause it to leak. Any ideas or suggestions? Has anyone else ever had a similar experience?

[Bordercollie]

Check the rubber flex hose that connects the filler to the tank, should have leaked with a full tank though if loose connection or crack in hose (??)

[VA-Apraisr]

Wow, 13-gallons lost while sitting? Hope you can figure this one out and give the rest of us a "heads up" on what the problem turns out to be.....that's a lot of fuel going somewhere and definitely a dangerous situation that could result in a serious fire. Good luck.

[T18skyguy]

If it's getting to the evap system as described above, one way to help stop that is to only let them pump till it clicks off the first time. Don't let them keep filling more after that, it's a known culprit for getting into the evap.

[Cougargm]

It stopped dripping when I took it to the garage (isn't that usually the case?). I put the bucket underneath and then went in the shop. When I came out the bucket was empty...so it actually stopped as I drove the 10 miles to the garage.
The mechanics didn't look at it right away since the bucket was empty and when they did look underneath, they didn't find a leak.
As for the amount, visibly I only saw two small drops continuously coming down from the bracket...enough to a pint in the bucket from that afternoon through the next morning. However, I'm not sure when the leak actually started. (It's parked across the street from my property) I filled it up the end of September, and ran the genny briefly once in Oct (though I didn't smell gas then). When I winterized it, the tank was down almost a quarter of a tank (about 13 gallons).
Yep, it is an E series Ford.

[time2roll]

Did the shop tell you what is above those brackets? I would be pulling stuff apart but I hate working on overhead fuel systems.

[Grit_dog]

There aren't too many places fuel can leak form and you already know "where" or close to where it was leaking from.
You said everything about the mechanics except "they crawled under the vehicle."
Guess I'd go for look under the vehicle with my own 2 eyes before digging in further.
You alluded to it lost alot of gas. IE you think it was leaking continuously for...however long.
I can't explain the mysterious "fix", but a large leak, to me, sounds like the fuel tank, or a hose/drain? coming off the tank. Does a gas generator feed off of the main gas tank?
Lines/filters/evap system would seem to only leak a little until they were empty until the vehicle was run again.

If any large amount came out, you may be able to see at least some evidence of where it was running.

[ernie1]

Don't know what chassis you have but the E series Fords had a gas filter in that location and is held in place with a banjo spring which requires a plastic tool that slips over the line to relieve pressure on it so that the filter can be replaced.

[carringb]

One more thought....

What about the generator fuel line? This line is protected by a solenoid, so it won't pump fuel all the time. Only when the generator is on (even just the ignition, it doesn't have to be started).

[carringb]

Cougargm wrote:
I wondered about that, Carringb, but I filled the tank the end of Sept. and it was leaking in early November. And I lost a lot of gas; wouldn't that have only burned a gallon or two?

The evap purge cycle doesn't occur all the time. I'm not sure when it calls for it, but it's definitely periodic. But no, I would not expect it to result in a massive fuel loss. Keep in mind a very small amount of leaking can cause a big puddle.

The reason I gravitate towards this theory is the intermittent nature. The rest of the lines are all under high pressure, so a leak is VERY noticeable. The only other thing that crosses my mind is a cracked filler hose, over the tank. But that *should* leak near the tank, unless it dripped onto the frame rail, and migrated away on the frame.

[toedtoes]

I would have them do a smoke test.

I had a gas leak in my clipper when I bought it. The mechanic couldn't see it. Did the,smoke test - smoke was coming out of the entire length of fuel line from little pinprick holes.

[Cougargm]

I wondered about that, Carringb, but I filled the tank the end of Sept. and it was leaking in early November. And I lost a lot of gas; wouldn't that have only burned a gallon or two?

[carringb]

Did you recently tip off the tank? Due to the intermittent nature, I'd suspect the tank got over-filed and some liquid got sucked into the evap system, which has a vacuum line returning to the motor to burn the vapors. This system is not tightly sealed.

[ksg5000]

When I had gas smell in Audi the mechanic used a device which pumped something that looked like smoke into the fuel system - using that device the leak was easy to find/identify.