1996 civic 1.6 ltr.... cat will crank and sometimes starts then dies... or just doesn't start at all.... usually driving car with barely any gas so I assume the gunk build up on bottom of tank has clogged filter... before this started car drove great. Amy ideas

 

Pull brake handle up. Watch the "Brake" light on the dash while you're trying to start. (It is on the same circuit as the ignition). The light should be on all the time you are cranking and after it dies. If it goes out that usually means the ignition switch is bad.

 

When you turn the key to on ll do you hear the fuel pump prime?

 

Well it could be many things, like mentioned when you turn the key to just the on position do you hear the fuel pump prime? If it primes try priming it a couple times by turning the key off and on and then try starting and see if that helps.
You talk about a clogged fuel filter? Pretty cheap and easy to replace? Couldn't hurt too much to pull the access panel off the fuel pump area and pull the fuel pump and maybe take a look if that is what you think it is. Get a fuel pressure gauge and see what kind of pressure you have.
Also check your plugs? Have you checked for spark? I would go ahead and crack open your distributor and see what your cap and rotor look like.

 

Post the CEL codes.