On the 2000 Jeep Cherokee Sport I have' sometimes when I return to
vehicle I pick up a very slight odor of gas. As if there was a gas leak
somewhere.
I have checked ground appearances under Jeep also fill cap pipe and
gas cap area and see nothing. This is a now and then thing that I notice
this.
I also was wondering how this sealed system works because if your gas cap is not on tight then your dash indicater trouble light can come on. Can
a minor gas leak somewhere in fuel system cause same effect? Note the odor when picked up is near back of vehicle and seems to disipate quickly.

Any ideas .

Have you change the fuel cap? It is only $15 (I use a locking one).

Then tighten the hose clamps under the fuel filler after you take the shield off.

Multi port fuel injection?....one or more injectors could be leaking..could be caused by o rings or injectors are leaking

Throttle body fuel injection?....only 1 injector..on the throttle body...could be leaking...

Carbed?....fuel leaking a carb...

Starting from the gas tank...check all hoses and clamps....follow the fuel line all the way to the engine compartment...There may be "quick connects"at the fuel rail....these have o rings that have been known to leak..the quick connects can also be replaced...get em at most auto parts stores..

Fuel leaks are not something you want to guess at....