Need help with a noise under gas lid

[zachem2]

I just bought a 00 Boxster S and I am trying to figure out if a noise is normal or if it is a problem. The noise is coming form under the fuel lid and it sounds like a air compressor or some kind of pump. I found a hole on the front side of the fuel compartment under the fuel lid, when I put my finger in the hole the noise stops. Does any one know what this is and what the hole is for. Please help

[goldenwarrior1]

Do you have a CEL? That tube is part of the EVAP system. The purge cycle should run once when you start the car cold but not continue to run. The pump should shut off once the system has purged and the system shows no EVAP leaks. If the pump continues to run then you have a leak and should also have a Check Engine Light. The vent tube that attaches to the gas cap well has a plastic clip that holds the tube in place. Check to see if that is cracked and vibrating.

[PTEC]

I just bought a 00 Boxster S and I am trying to figure out if a noise is normal or if it is a problem. The noise is coming form under the fuel lid and it sounds like a air compressor or some kind of pump. I found a hole on the front side of the fuel compartment under the fuel lid, when I put my finger in the hole the noise stops. Does any one know what this is and what the hole is for. Please help

Check your ORVR valves, you likely have one stuck open.

[zachem2]

Thanks for the info.

The pump does run and then shuts off. It doesn't run all the time. I didn't have a check engine light, then I hit a huge pot hole and it came on. I pulled the obd codes and I am getting code 0650 Malfunction Indicator Lamp (MIL) Control Circuit Malfunction error, so now I wonder if some one tried to disable the CEL before they sold the car. The CEL seems to have issue, OBD always comes back with 0650, but the CEL is not always on.

Back to the pump running, I don't think mine has a vent tube attached to the gas cap. Unless the ruber thing that keeps the gas cap from falling is a tube. I do have a hole and when the pump runs I feel something (I think pressure). If I put my finger over the hole the pump stops running.

When I get home this evening, I will take a picture of under the gas lid. I maybe missing a hose.

[PTEC]

There is no pump for the tank vent system. What you are likely hearing is the tank vent purge cycle. The DME opens the tank vent purge valve which allows engine vacuum to pull the vapor out of the carbon canister. When the fresh air valve (which is part of your ORVR system) sticks open you will hear this noise during the purge cycle. Having this valve stuck open will not cause a check engine light or any other problem. The hole that you are putting your finger over is connected to the fresh air valve of your ORVR system which is why putting your finger over it changes the sound.