Weird fuel pressure issues

[Nightprowler1019]

Been having issues the last year with my 97 k1500. Long story short fuel pressure is 48 at idle which I know is way to low. 54 koeo. Raised rpm goes down till 1500 then slowly goes up to 52. Shut truck off or after priming system pressure drops fast to 20-30. I crimped the return line pressure went to 80-90 then it dropped really slow when I released it. No leaks, new delphi fuel pump, new filter, delphi spider and regulator last summer. Checked relay, grounds and power to the pump which it gets 11.96 volts when priming. Im kinda at a loss as of where to go next any help would be greatly appreciated

 

[someotherguy]

How is it actually running? Pretty much everyone I've seen check their pressure after replacing the poppet valve setup with the individual injectors (often referred to as MPI or MPFI) the running pressure is lower than spec, with no issues.

Richard

 

[Nightprowler1019]

It has a random misfire at idle and surges around 1500rpm that I've been trying to track down with no result. Cold start is normal. One thing I've noticed is on hot starts if I let the pump run then start it dies then hit key again it starts right up but if I just hit key it fires up every time. Ya know never though about the mpfi spider running with lower pressure...makes sense though