1992 Cadillac won't start

I checked the fuel pressure yesterday before I changed the fuel filter. It was a little above 40. Yesterday when I pressed the valve for the fuel pressure no fuel would come out. Once I changed the filter and pushed the valve fuel came out really good. So the pressure is probably better now. A friend of mine gave me his fuel pressure gauge to use yesterday. Also yesterday when the old fuel filter was on the engine wouldn't even turn over. Once I put the new fuel filter on it started to turn over. How do you check for injector pluse. My friend also came over and tried turning the crankshaft wheel with the belt on it. He turned it as if he was tighting it. When he turned it it was going good then it stopped to where it wouldn't turn anymore. He had to loosen it up as if he was taking the crankshaft pulley off. Then he took off the belt and im not sure if it seized up on it either. He checked the rotor and the distributor cap and said everything looked good their to. He also poured gas in the carberator and the engine would crank but didnt fire off.