[jccollins]

the gas smell is present as long as the car is running and it dissipates shortly after being turned off

 

[frankp]

could be cracked or broken evaporative canister lines in hatch area on pass.side behind panel above the wheel well,or behind the panel that covers tail lites.

 

[martinzx]

I would check your fuel injectors. Ive heard that Z's are notorious for
leaky fuel injectors. I had this same problem (on my '82 280ZX) and
it was the injectors. Just pop the hood and see if you see fuel around
the injectors. Alot of times those plastic seals around them crack.

 

[fjm280z]

Also check the fuel hoses leading to the Fuel injectors, make sure clamps are tight. Sometimes the clamps could be loose therefore causing a leak.