Not saying that it is, but it's possible that your rubber subframe bushing on your S14 may be bad. Usually you will hear a clunking type sound whenever you step on the gas. S14's are notorious for this problem. Click on the attached link for additional...
Driftopia Tech Blog » Blog Archive » 240sx Subframe Spacer Install
As for the gasoline leak, jack the rear end of the car up and crawl underneath there with a very bright flashlight. It's possible one of the gas lines underneath the car may have a cut in it from road debris kicked up while driving. If you're lucky that will be your problem..a cut/torn gas line. The S14 gas tanks are made of a pretty hard plastic and doesn't often break. If the gas tank is punctured, then best bet is to find someone in your area that is parting out a S14. You can probably work out a deal with them about the purchase price. Replacing a gas tank is a MAJOR BEYOTCH as you have to drop the rear subframe.
Anyhow, hope this helps...
Good luck!!
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