Fuel/Ign Starting problems
I have a 2001 Cadillac Seville SLS that has been having Intermittent starting problems. Presently the vehicle will not build-up fuel pressure in order to start to 41-47 psi unless I remove the rear fuse/relay box IGN 1 micro relay. With this relay removed, I can hear the fuel pump build-up the required psi and then I confirm the build-up of that psi by looking at my test fuel psi guage under the hood, the car then starts no problem, and runs no problem with relay not installed. Whenever I re-install this micro relay the fuel sys will not build-up the required psi, it just stays at 0 psi, and of course it will not start. I just replaced the fuel pump sending unit assy plus fuel filter today.

What is in the wiring diagram that can cause this problem??? Tried swapping micro relay with other positions and still same problem which confirms the relay is not bad.