Boiling Fuel?
When I return from a drive with the tank around 1/4 full or less, I call hear what sounds like the fuel is boiling in the tank. I can take the cap off and still hear it. I put on a new tank over flow hose so I know that is open. Years ago I had the tank out. I don't remember ever putting anything under the tank before I replaced it. The assembly manual doesn't seem to show any detail in this area. I notice under the tank looking up when the car is on the rack, two round open holes in the body under tank area (probably 2 inches diameter) I am reasonably certain they are original. Is there supposed to be an insulating pad under the tank? Are those holes meant to be open. I'm wondering if the muffler which comes up fairly close to the tank area could be heating the fuel. I live in Australia and when I have the car out, outside temperatures are usually between 80 - 100+ F but the car isn't overheating- maybe slightly at a really long stop light. I use the highest octane I can get at the pump and often add octane booster. Any ideas out there what might be causing this and what to do about it??
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Re: Boiling Fuel?
Richard Do you have an IR temperature gun? If not try borrowing one and check the temp of the mufflers and the underside of the tank. There is no insulation in this area. There are two strips that keep the tank straps from rubbing metal on metal but they do not insulate. The two round holes are suppose to be there. Could the muffler have a small pin hole in it? Are the mufflers stock in dimensions? If too big maybe they are getting too close to tank. Keep us informed Terry -
Re: Boiling Fuel?
Exhaust system including mufflers are reproduction stock type from probably 20 or 30 years ago. I did inspect mufflers while on the rack recently and there seems to be no sign of leaks. Should I be concerned about this or could it be a common situation? I'll check the muffler temperature, but I haven't got a clue what temp range it should be in when hot. Thanks, RichardComment
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Re: Boiling Fuel?
Mufflers heating the gasoline in the tank is a common event for C3s. I expect it is also common for C2s given their common under car construction. It is only with the more modern low vapor pressure fuels that this has become a problem. I would bet the addition of alcohol has not helped the problem in this country. I am not sure what you get for gasoline in Oz.
If you like driving your Corvette in your warmer months, I think this is a problem you will have to live with. The boiling is likely occurring where there is suction, which equals low pressure and boiling at a lower temperature, at the fuel line to the fuel pump at the passenger side frame rail. This can and will lead to vapor lock. Anything you can do to insulate that fuel line from the heat of the adjacent muffler will be a help.
OT: The mufflers for the C6 heat the luggage in the storage area very well. Many of us have learned to be careful where we store temperature sensitive items in our C6s. The center console is no better a place in a C6.TerryComment
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Re: Boiling Fuel?
The residual heat of the mufflers is not sufficient to raise the contents of the fuel tank to the boiling point. I'd be interested to learn what the average fuel temp increases to after shutdown. It would be easy enough to lower a thermometer on a string. Don't tell SWMBO.
My guess is that the gas in the fuel pump is going through vapour lock and the gurgling sound is being transmitted via the fuel lines.Comment
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Re: Boiling Fuel?
I agree. I doubt if the fuel in the tank gets much over ambient, but the fuel lines through the engine compartment and fuel pump are likely well over 150F. The more common condition would be vapor lock, which will cause the engine to stall or carb bowl percolation, which can cause poor idle and difficult hot starting.
There have been many discussions on these topics, and owners have found significant measured temperature reductions by wiring the heat riser valve open and insulating the fuel lines through a engine compartment. It's all in the archives.
An IR temperature gun has become a necessary tool for vintage car owners, and a little ingenuity goes a long way in mitigating vapor lock and percolation issues.
DukeComment
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Re: Boiling Fuel?
I feel better in the knowledge that this may be a common problem and that it is unlikely that the car is going to burst into flames. (at least not from the percolation issues) It won't look nice, but I'll try insulating the fuel lines and I'll probably invest in a heat gun soon too. Thanks all, RichardComment
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