Gas cap vacuum
#1
Pit Crew
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Gas cap vacuum
Is it normal for the gas tank to be under a big vacuum? My 97 300 is the only car that I've ever owned that makes a big sucking sound every time you open the gas cap. It's been doing this ever since I bought the car many years (8) ago and it runs fine. My worry is that the cap or system isn't venting properly and that it will eventually toast the fuel pump. My other cars, including an LS, might have a slight vacuum relief hiss, but nothing like my SC produces. Anybody else notice this?
#6
Pit Crew
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Back in the days of mechanical fuel pumps my Dad's car would shut down for no obvious reason after it had been driven for 20 minutes or so. After sitting for an appropriate length of time it would start back up and everything would be good. He had the dealership look it over and they replaced the carb.....no good.....then another shop replaced the fuel pump.....no good. Someone diagnosed the problem as being vapor lock and they wrapped the fuel lines in aluminum foil. This went on for 6 months or so until he pulled into a station for gas (this was before the days of self service). The attendant went to put gas in an heard the whoosh. He walked up to the drivers window and said, "sir your gas cap is not venting, probably rusted shut. If you don't replace it it'll build up vacuum in the tank to the point that your fuel pump can't overcome it and your car will shut down due to fuel starvation." 2 bucks later, problem solved.
I know modern fuel systems are designed completely different to eliminate gas emissions escaping from the system, but you'd think that there would have to be a one-way vent to allow air to replace the volume of fuel pumped from the tank.
I know modern fuel systems are designed completely different to eliminate gas emissions escaping from the system, but you'd think that there would have to be a one-way vent to allow air to replace the volume of fuel pumped from the tank.
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#14
Mine friends bought a sc that needed a new gas tank. So he got one from lkq. Well it was a little warm dkwn here in texas yesterday and his trunk gets so much pressure the gas cap will shoot off if ur not carefull. He said it expanded and dented out today... Maybe this IS somethi g to wkrry about
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