So my 1994 k1500 (4.3l) truck starts after cranking for about ten seconds once it achieves high enough oil pressure I tap the gas then it starts, however after driving at highway speeds for maybe 10-20 minutes it won't start after shutting it off until it cools down. Originally it wouldn't start at all until I bypassed the relay by feeding power from the coil to the other side of the fuel pump fuse with a switch. Brought it to a local Mechanic who fixed some pins to the ecu so I dont need the switch anymore but it still has the same problem of starting off of the oil pressure and not starting again after driving it. I have replaced the relay and the oil pressure switch and neither one did anything, any recommendations on how to fix this?