1998 chevy s-10 p/u 2.2 ltr.starts only when it wants,turns over,has fire at plugs,has fuel pressure at fuel rail,when it starts it runs great!!! any suggestions would be appricated.also security lite blinks on instrument panel

So you know it is not getting fuel thru the injectors.
Have you checked fuel pressure at the rail, and do you know if the pump is running when you turn the key on ?

Inside the intake manifold.

Three systems in engines:

Fuel delivery (fuel mixing with air to burn and making it to the spark plugs)

Ignition (lighting the fuel on fire)

Compression Building up pressure to fire the fuel
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It is possible your engine could have low compression if it has ever been run low on coolant or oil. The engine might spin or turn over but not have fire at the spark plugs. If you are correct that the spark plugs have fire but it will not "kick" or run then fuel delivery is where I would start. See if your fuel rail has fuel in it by pressing the fuel rail valve:

If you have fuel there under a good amount of pressure see if one of the plugs smells like gas after cranking. If so the problem is not the fuel, move on.
If you don't have fuel at the Schrader valve the problem is in the fuel pump and system.
refer to a manual on how to remove the pump from the tank and replace it. This problem has signs before it goes bad. Hard starts and running rough when hot.

Good luck

Check to make sure it is getting fire. You can also hook a pressure gage to the fuel check valve should be near the fuel rail to see if you are getting a good constant fuel pressure. usually fuel problems will let the truck start but not stay running unless you are getting no fuel at all if thats the case it usually means your fuel punp is not working. with your key turned on your fuel pump should be running you can just bleed the check valve to see if you are getting any fuel pressure at all if you are getting none check the fuses and see if you are getting any power to the fuel pump if the fuse is blown then you can try to replace it if it blows again the fuel pump is bad or you have a short somewhere most likely.

Check Fuel Pressure. First turn key to on position (without starting) and listen for the fuel pump motor. If no motor sound, your fuel pump is not working. Check fuel pump fuse and relay. If fuel pump works, check for pressure at the fuel rail (schrader valve on fuel rail for pressure testing). If no pressure, or not enough, fuel filter might be clogged or fuel pressure regulator may not be working properly. IF fuel is not the problem, start checking electrical, such as ignition control and proper spark to plugs.

Sounds like the fuel pressure doesn't build up right away, before you crank the engine, just cycle the key from off to run position a couple times to allow the fuel pump to build pressure and then crank...if this still doesn't work, hook a set of jumper cables up to it and then crank...the extra voltage will allow the pump run faster and may fire right off....if this helps in starting, i would suspect a weak fuel pump.

The proper fuel for this s-10 is 58 psi to start the vehicle and it will run on 45 psi but not to good .:)

Check the fuel pressure, bad fuel pump or sock on the fuel pump and fuel filter check spark plugs and check distributor cap, a fuel pump is $273.00 or a bad injector $110.99 or BWD Fuel Vapor Pressure Sensor for $35.99 any of these parts could cause the problem, so without doing a fuel pressure test it is a guess, if the vapor switch is bad it could cause a long crank time if the fuel pump is bad it has a check valve in the fuel pump, if the check valve goes bad the pump can't maintain fuel pressure so on start up the fuel has to pump from the tank all the way up to the fuel rail, if the injectors is bad it could leak after engine shut down and cause you to lose fuel rail pressure. Also the fuel vapor sensor could be stuck open and could cause the problem, all need to be tested, you can rent the fuel pressure tester from AutoZone or advance auto or Shucks they return your money when you bring the tool back as long as you buy the parts to repair it from them. That would be the first thing I would check fuel pump pressure and if you replace the pump then change the fuel sock as well. That model was not meant to burn ethanol and can kill the fuel sock the fuel pump and filter.

check your entire ignition system especially the ignition control module

You need to check the fuel press, the test port in on the rail, also run a code test on the ECM/PCM, this checks for trouble codes and also lets you know the computer is working if it tests ok.