Nissan Repair: 1999 Infiniti QX4 gas tank problem, 1999 infiniti qx4, infiniti qx4

Question
Hi, I hope you can give me an idea what could be wrong with my daughters 1999 Infiniti QX4.  A while back I noticed soot around the gas door and the door was bent so that it was hard to close.  I thought some kids at the college had pried it and put some kind of fire cracker in it.  I took the door off and straightened it as best I could and now it closes o.k.  I cleaned the soot off, but it keeps returning.  The inside around the gas cap is sooty as well as the inside of the door.  Can you suggest some possible remedies to this problem?  I must say this is the first time I've ever seen anything like this.  Thanks.

Answer
Dorthy,

First, when you say soot I think of exhaust as the cause.  If the check engine light is not coming on from a defective gas cap as in fuel system pressurization leak.  I would think there is a hole in the exhaust or the tail pipe is short and allowing the exhaust to backup and vent up at the gas fill point.  Let me know if the soot you describe is black and dusty or greasy.