1995 saturn sl2 crank but wont start

let me start at the beginning. About 2 weeks ago i went to a local store for some things I needed. drove about 10 miles. went inside and when I came back out the car wouldn't start. let it sit about 15 min and it started right up. ran good for another week. Today I drove it about 10 miles to work. when I came out at lunch about 3 hours later it wouldnt start again. tried 3 times then it finally started. then on my way home it just died on the road. had it towed home. I used a spark test to check for spark. it had spark. checked the computer no codes. can see the tack move up a little while cranking. has good fuel pressure. put a noid light to check injectors. nothing. checked the wires with a volt meter has 12v. with car on but no ground signal. can a falty crank sensor give spart but no injector pulse or should I be looking somplace else. I also checked that the throttle sensor was working properly and it is. what can cause spark but no fuel injector pulse.