So over the weekend I installed a new Delphi fuel pump assembly to replace the failed Precision brand pump. The install really seemed to go well aside from fighting to get the lock ring to thread on again, lol. But I do feel confident it seated cleanly. After install, the jeep fired right up and idled down nicely. I installed a fuel pressure gauge at the rail and the psi read 49. After a few days I started the jeep in the morning and I noticed the pressure was much higher, in the 56-58 psi range. This of course alarmed me, but I found no leaks or anything obvious, the jeep runs very well, idles nicely, does not have the smell of running rich, no black smoke, the pressure needle doesnt bounce around, but it reads higher than 49.2psi. I bought another gauge to see if maybe it was defective, just installed it, and its reading the same 56-58 psi.
What are your thoughts on this situation? Do I most likely have a defective pump regulator... again? Could a defective fuel pump relay cause this irregularity in pressure?

 

Relay won’t cause higher pressure that’s on the regulator side. Most likely the new pump’s internal regulator is bad or wrong spec (maybe for a different model). 49 is normal for most Jeeps, 56-58 is too high. I’d return the pump and try another brand.