thats about 30 psi low

Okay sounds like a new pump is needed. Any recommendations for a model pump to purchase? Looks like the oem part isnt available anymore. I'll probably replace the regulator while I'm in there.

I used a pump from the ROP shop , $65, it's generic so it's a roll of the dice. You can buy an entire new cool fuel assembly with pump regulator and cooler from Merc if you are so inclined. $500+

Seems steep. I may just have to roll the dice. I saw some generic ones from QFS as well.

Also, there's another test you can do to check for pump vs. regulator being faulty.

With 12V to the gray wire, pump running, carefully and slowly pinch off the return line with a pair of pliers (use a rag on the jaws to prevent damaging the return line). As the line is occluded, if the pump is good but reg is bad, the pressure should be able to spike to 60+ psi (immediately release if you see this happening). If the pressure can't easily exceed 45psi with the return line pinched off, then the pump is weak for sure.

I've got a pump from a 98 Cool Fuel setup. It's used but was working well when pulled (I built new engines - carbureted). 400 hours per the ECM, but some of that could have been key-on-only time. You can have it for $50 plus the ride (I'm in VA). I'll throw in the regulator too (green stripe).

I also have a great set of better-than-OEM injectors that have maybe 20 hours on them if you're interested.

If on key up the pressure shoots to 60 but then drops off to 10 doesn’t that indicate a leak down? Once it achieves pressure when keyed up it should hold.

We eliminated that by jumping 12V to the pump supply lead. even while running continuously it only generated 10psi.

That could still be regulator bleeding off. Someone said block off the return. Did that get done?

I suggested that. Haven't heard back from the OP as of yet.