Back fire?

[Bluto]

When I sit at an idle in park, I notice a thump like sound every 5-10 seconds. I sit and wacth the tach, and it doesn't react to the sound. It sounds like it is comming from the back of the car.

Question is:
Is it possibly a back fire?
It even sounds like a gas can buckling.
Maybe the tank is not vented?

Any one have a theory?
-Bluto

 

[projectSHO89]

Go back there, listen near the fuel tank, and try to determine if it's a rumbling or gurgling sound coming from inside the fuel tank.

If so, the check valve on the fuel return line is bad.

Steve

 

[Bluto]

i'll try that
thanks