Chrysler Repair: 2004 Stratus: fuel system/tank noise after shutoff, vacuum leak detection, 4 digit numbers

Question
2004 Dodge Stratus Fuel Pump?
After I turn ignition off there is a purr (fuel pump?) around the fuel tank for about 1 minute if I let it be. If I remove the gas cap a big rush of air escapes and the purr quickly stops. Then there is a gurgle or two from inside the tank.. What is this?

Answer
Hi Doug,
This sounds like the natural vacuum leak detection system doing its 'thing', which is to detect any fuel vapor leaks. The system is designed to normally be at a slightly lower pressure than the environment when the vehicle is driven so the rush that you describe is normal. If there were an issue with the system it would probably be noticed as a problem in driveability or there would be a fault code stored in the engine cotroller. You can often get a free code readout at a nationwide autoparts store such as Autozone. Get the 4-digit code if any and let me know. You might also get a code readout with your ignition key:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer reading to see if the mileage changes to show any 4-digit numbers.
Roland