my 1991 mercury capri non turbo just starts then dies

I have replaced plugs, replaced pump, checked spark at plugs while cranking and that's good, pump stays on the whole time the car is starting and dying, by passed the double main relay and that's not the problem. like I posted if you let the car sit for 5 or more minutes it will just try to pop off then just crank. so you stop cranking and immediateky start cranking the motor again and the 10th or so time of doing that it wil then start and rev to 1500 rpm or so then die, and will keep doing that over and over as long as you don't let the car sit without starting it for 5 or more minutes. the belt does squeal loud once it starts.

I just tonight ran it for 5 minutes off a can of starting fluid. the fuel high pressure line does not have high pressure in it but the fuel return line sprys out gas when disconnected. and the hose does pump fuel back to gas tank through the fuel return line. I tried pinching my fuel return line off at the injector rai and that did not help. sometimes it just cranks and cranks and other times it will try to pop off, rev, then die. and just pops off sporadically but you can get it to run and run all you want spraying starting fluid into throttle body. does ANYONE have any ideas yet?? just ideas of what to try will help. I am a foreign car guy. got no clue what could be causing it in this car. I was told either the computer or the ckfp -crank shaft position sensor- built into the distributor. but it seems either the fuel return regulator not working and causing proper vacuum or its something else. I dunno. should not the high pressure line to the injector rail have high pressure// not the return line??