1986 s-10 erratic starting

Cold or warm start doesn't matter. Starving for gas during cranking. Does the oil pressure reading suppose to go to zero when the engine is turning over and turning my fuel pump off? Does the fuel pressure stay constant after turning the engine off for short or long periods of time?
Changed fuel pumps, checked pump wiring, changed pump relay, changed
fuel filter. Voltage reading at the fuel pump reads 8.7 when switch is on.
Frustrated in fort lawn.

OK we all know that electric motors in cars are built to run on 12 volts. I would check for corrosion on the wire conectors an clean them for good measure. (this is only if you are talking about your ignition switch is in the run and not start position) Even if it is when you are in the start position. my truck never drops below 10 volts while starting