2000 E430 fuel system not holding pressure

[SpaceCity E 430]

I looked through the DIY forum, and did a search, but can't find any new info that helped.

Situation: Car has been taking longer to start than typical. Two to sometimes three starting cycles. Last night and this morning after no start on the first cycle I pressed the plunger on the fuel rail shrader valve to check for any fuel pressure and found none.

Car received new fuel filter two months ago, and new fuel pump two days ago. The fuel pressure regulator for this car is in the fuel filter.

I'm *thinking* it's the fuel pressrue regulator that's in the fuel filter. I have another fuel filter to install, but before I do I would like to know if there is somewhere else the fuel pressrue could be bleeding off to? It's not going by an injector and bleeding into a cylinder. Engine runs like a top once started.

Many thanks.