1995 chevy s-10 4x4 ls wont start

it has a new sending unit , ignition module and it seems to have good spark plugs and wires. is it possible that the fuel pressure needs to be ajusted? the tank was down for some time before re-installed. or maybee it isnt getting the required spark it needs to turn over? if so how can i check for spark or could it be the fuel pressure regulator?

First, you can do an easy fuel pump check. With your door open and radio turned off turn the key to the "on" position. You should hear a buzzing sound from the gas tank area. If you don't then turn the key back to off and wait a minute or so. Now crawl under the truck so your gas tank is right above you and have someone else turn the key to the "on" position. If you don't hear a buzz from the tank then either your fuel pump fuse or relay is bad or your fuel pump is bad. If there is a buzz I would check spark next.
To check if spark is getting to the plugs do the following but BE CAREFUL!!!
Turn off your vehicle. Unplug one of the wires from a spark plug, the #1 plug should be easy. Take a phillips head screwdriver that has a thick plastic handle and stick it into the spark plug wire. With a clean rag wrapped around the screwdriver handle, for extra shock protection, place the metal shaft of the screwdriver close to something metal but don't let it touch. Now have someone else get in the truck, turn the key to start, and release it about .5 seconds. You should see a spark transfer from the screwdriver shaft to the metal it is next to, if not try it one or two more times to make sure. This way you will know if it is your ignition or fuel. Again, please please please be careful when doing this. I got shocked once from a spark plug wire when using the old style timing guns, not the inductive style, and it didn't feel too good.
Next i would get a fuel pressure gage and check that.

on my 91 i have to keep wire dry on wires cap and coil,also there all new....does it seem to not start when it's cold and raining,or snowing????

First order of business is to make sure the battery is fully charged. A weak battery will still crank the engine over like nothing is wrong, but with a weak battery the starter will draw all the current and not leave enough for the fuel pump to reach a prime of 60 psi. (Been there done this on my '95) AutoZone will check the battery for free with a load type tester.

Next get a fuel pressure gauge and check the fuel pressure at the schrader valve, located on the driver's side of the distributor. It must have at least 60 psi when the fuel pump is running for the engine to start. If you don't have 60 psi at start up, the injectors will not fire.

When you turn the key on, (engine off) the pump only runs for 2-seconds and then the key must be off for 10-sec before the pump will run another 2-sec. Then watch the leak down rate when the pump shuts off. If the pressure drops below 55 psi within 2-3 minutes you have a leak down problem. You can borrow a fuel pressure gauge from AutoZone, etc. or buy one for about 35 bucks.

If the fuel pressure is at spec's, then get a spark tester at the auto parts store, (sell for less than 10 bucks) and check for a good blue spark at the end of all the spark plugs wires. (Yellow spark is not good) Just because one spark plug has spark doesn't mean the rest of them do, so check all.

Post back what you find and we help you further if needed.

DelCoch, I agree with everything you said but would add that before getting a fuel pressure gage it is easy to listen for the fuel pump cycle. If it doesn't cycle when the key is turned to the on position then a pressure test is a waist.

Not to be too simplistic, but have all of the fuses been checked? Did it run before you dropped the tank to replace the sending unit? If so, I'd recheck the connections if the pump isn't running or isn't putting out enough pressure. Also, on the S-10s and Blazers, it's never a bad idea to replace the rotor and cap, they're noted for being a weak spot.