replace it.

I've had good results with a gas tank repair kit from NAPA.  It's an epoxy
with a nylon fabric reinforcement.  I've used it on a gas tank and on a
washing machine.  Both are holding fine.  Make sure you mix the epoxy well
and follow the instructions carefully.  First time I used it, I mixed it too
long and the epoxy cured before I could spread it.

-Bruce

There are companies that repair the plastic tanks with a 'welding'
process.  You should check the yellow pages, there are a bunch in my
city that repair plastic tanks.  I ripped the corner out of mine and
they said they could repair it with success in their belief, but the
hole was too big to warranty....

I ended up with a good deal on a used tank.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
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You say it's a small hole. What does that mean? Where is the hole? If
you want ideas you need to supply information. If it's a round hole the
size of a BB that's different from a small leak that is coming from a
crack, which is bound to get larger. It takes a special compound to
stick to that material. It's expensive and toxic. Plastic welding is
the potential cure. You can buy a small maching from Harbor Freight. Or
you could take the tank somewhere. I suspect your goal is to fix it
without removing the tank. In a pinch, I would favor the hard type of
epoxy that you knead in your hands. Sand the surface rough first so it
will have something to grab. Dry the area with brake cleaner or
acetone. Knead the epoxy and hold it up there until it begins to cure.
See what happens from there. You will always need to be watching for it
to break loose.