gas problem

[84_Sportscoach_]

We have a Sportscoach III , on a C-30 chassis, with a 454 in it . Made by Chevrolet before Sportscoach was taken over by Coachman. It has a 100 gallon gas tank on it . We took it out for a test drive and an overnight 4 or so months ago and we nearly filled it up , gauge read 3/4 , See I had 4 5 gallon cans full of gas here so I put 3 in and on the forth one the tank overflowed . The fill pipe has an overflow catch tube that goes back into the tank . Any way so the overflow made it smell like gas in the coach so bad that I put a fan in there to blow it out . Also I siphoned out 2 gallons to hopefully prevent any heat expansion from more overflow and smelling things up again . The smell got worse so I siphoned another 3 gallons out . The smell persisted, then yesterday the gas level was up to the overflow tube and gas was visibly leaking along the right rear side where the full tube is located . So I siphoned out 3 more gallons ... That's 8 total gallons . I could see the gas level about a foot or more down the fill tube . I am flummoxed, no way that was heat expansion.. Afterwards I hear a plop plop like a bubbling coming out of the Overflow tube and I put my finger over it and it stopped ... It was like there was air coming out but just a bubble at a time ... So I started it to see if maybe there was a vaporlock or something in the system..It started right up and ran no problem . Went and looked at the level again and it was the same ... I can't figure out what it could be . We plan on driving it at least 2,700 miles in a months time and I do not want this to happen again . My wife, " the plumber's daughter" who always finds the leaks before I do mentioned there could be water in the tank .. But 5-8 gallons would be on the bottom of the tank and it would definitely not run well or at all like it did . Also the tank gauge is apparently broken or the sending unit is stuck on 3/4. Any ideas out there on what it might be?

[84_Sportscoach_]

To Matt Colie , Thank you . I did replace the hoses ,(filler and vent ), from full station to tank . I plan on going thru and replacing all lines from tank to carb when we get home in the spring. Thanks for the comeback .

[Matt_Colie]

eHoefler,
Jeremy's user name is 84 Sportscoach III.

I can tell him (at great length if he cares) that he might as well plan to have the fuel tanks down now. This as the owner of another seasoned coach. He can count on all the rubber in the fuel system to be shot and it was probably not alcohol compatible to begin with. It usually requires that the tanks be taken down to replace all the fuel lines. While there, there are big o-rings that seal the sending units in the tanks. If it is new enough to have in tank pump(s), then those and the level senders might as well get replaced at the same time.

Do I have to add "Been There - Done that" (look at the coach in my pic)

[opnspaces]

Drive it around the neighborhood making sure to go up and down a few small hills. That should allow any air bubble in the tank to migrate up to the gas cap.

[eHoefler]

you didn't mention the year of the coach, but i would check the fill hose and the vent hose, they may need to be replaced. Also, replace the gas cap, they are suppose to hold pressure in the system

[valhalla360]

wa8yxm wrote:
Two thigns.
1 Gas gauges are often a bit 'OFF' as to how much gas you have in the tank.

Second.. Rock the baby.. ER.. Tilt the RV away from the fill tube for a few minutes... Just a little bit makes a big difference.. you can go 1-3 degrees (Try for 2) that's about 3" higher on the filler neck side of the RV.

Yep, there may be an air bubble trapped near the top. Air expands more than liquid for the same temp difference. When it does, the liquid is forced out (and could explain the bubbling noise as it gets down to the point where some air could escape).

[wa8yxm]

Two thigns.
1 Gas gauges are often a bit 'OFF' as to how much gas you have in the tank.

Second.. Rock the baby.. ER.. Tilt the RV away from the fill tube for a few minutes... Just a little bit makes a big difference.. you can go 1-3 degrees (Try for 2) that's about 3" higher on the filler neck side of the RV.