GM-GMC: gas smell, gasoline smell, harry jacobson

Question
Hi Harry Jacobson, P.E.


I drive a 1992 nissan maxima with 180,000km

Last year, I replaced the gas filler neck because I could see gasoline leaking from the rusted pipe. I have no gas smell since then but now I have gasoline smell again near the similar area. The gas smell is from the back.. not the front.

last time .. the filler neck is leaking gasoline on my driveway

this time.. there's gasoline smell but no gasoline on the ground

Could you give me some idea where the gas smell is coming from ?  .. what part could be leaking gas ?
the smell is from the back,, is not a major leak because there's no gasoline on the ground.. i don't see any gas leaking from the gas tank, i can't see the top part but the bottom part of the gas tank have no leaks..


Could you give me some idea where the gas could be leaking from ?

Answer
Gasoline vapor can travel a long way but the liquid does not, especially from small leaks.

It is likely that there is a pinhole somewhere.  On a hose, the top of the fuel tank, in a metal tube, or even from the fuel cap itself.  The hole may a few feet from where you think it is, too.

I am afraid that you may be in for an extended session of trying to hunt for the leak.  The one trick you might want to try is to disconnect the fuel line as close to the engine as possible and plug it securely.  Then, take some low pressure compressed air, say 2 to 3 psi, and pressurize the fuel tank at the fill neck (use a rag to help seal in the air).  You may need someone else to ensure that the air hose and rag stay put.  Then try to listen for air/gurgling fuel under the vehicle and along the plumbing towards the engine.