Replace the injector. Do not drive the car till it is replaced.  I'd go
ahead and replace all six injectors because the car is 26 years old and
eventually the others will go bad.  New ones are not cheap.

Try google for replacement instructions using search terms like replace
fuel injector for 83 280Zx.  There are complete shop manuals online and
self help sites, despite Nissan's quest to shut down such websites giving
away free info.
You can shop manuels at most bookstores online. I know ebay sellers have
them for your car on
CD-ROM and paper print.    

It's the injector, the seals don't create a fuel leak and rarely is it the
hose.

yes, they all need to have the same flow rate and mixing brand/age injectors
creates all sorts of mixture distribution problems. Some info that may
help, 84-86 300ZX non-turbo top feed injectors are the same as the
non-turbo 280 injectors.

I've seen all three problems.  I currently have a porous hose on my daily
driver ZX, I've had leaking seals, and leaking injectors.  I'm fabbing a new
fuel rail out of aluminum stock to make the job easier in the future.
Here's a link for all of the parts you might need.  I've had good
experiences with this company, but there is always ebay.
http://www.courtesyparts.com/s30-s130_inj.html

geotek