I just did a 5.7 vortec with complete harness & interior swap on my 92 gmc. Everything came out of a 99 Tahoe except the trans. I kept my 5speed. During the swap.. I installed new spider, fuel pump, distributor & gaskets. I'm now getting a crank but no start. (Starts momentarily ) with the key on i get 50psi when it tries to start the pressure drops to about 40psi. I already swapped pump & filter... But I'm only getting 50psi to the fuel rail. I checked the pump before the filter & get 85+. I got everything connected back up & same thing.. So I pinched off the return line at the tank & still only get 50psi for just a second then drops to 45. Any input would be greatly appreciated.