I would expect so, but I don't think it would be significant. There will only be vapor there, not liquid, so the fuel will have to evaporate to be lost. You should get a Check Engine light though because that is part of the evaporative emissions system and it gets pumped up to about two pounds of pressure to test it for leaks. You should get a fault code for a "large evap leak". That's the same code as when you forget to tighten the gas cap.
In addition, you will be able to stuff too much gas into the tank. There is about a five to ten gallon air pocket in the top to allow the tank to crush in a crash without rupturing. I know that I have a leaking gasket on the top of my rusty trusty '88 Grand Caravan daily driver. Because of that, if I wait a few seconds after the gas pump clicks off, I can get another half gallon in before it shuts off again. If I do that long enough, I can get 24 gallons into my 18-gallon tank, then it starts to run over onto the ground. The gas sits in the filler tube until the air slowly seeps out through the leak.
I would head to one of the pick-your-own-parts salvage yards to find a replacement valve assembly. There should be an access plate in the trunk floor to get to the pump, but I don't remember if that valve can be accessed there too. If you're anywhere between Ohio and southern Georgia, do a search for "Pull-A-Part" and see if there is a yard near you. All of their yards are very clean and well-organized. Employees and customers are very friendly, and parts are REAL inexpensive. You pay your buck, throw your tool box in one of their wheel barrows, and you can spend all day there. The cars are already well-supported off the ground about a foot and a half in case you need to crawl underneath. If you broke your old valve by pulling it out or stuffing it back in, take along a spray can of Silicone Spray Lube. Pry the valve up a little, then spray the gasket. The stuff goes on like water, evaporates quickly, and leaves a film of slippery behind. It works great for sliding rubber parts like heater hoses over metal parts.
Tuesday, February 5th, 2013 AT 5:04 AM