the pressurized circuit after the pump and to the injectors should hold pressure.
i'd say the little rubber tip seal in the pump top port assembly is kaput.
instant bleed down.
everything you want to know about these pumps is here.
i have rebuilt mine.
http://www.914world.com/bbs2/index.php?showtopic=350416but i do not know where you would get that little rubber tip seal that is inside the 3 port assembly at the top of the pump. fortunately that tip seal was good in the two pumps i fixed up.
i've tested mine since rebuild.
the bleed down on pressure is very slow when its like a proper functioning pump.
still holds pressure 24 hours later.
not at 28 lbs but its still got pressure.
35lbs is high.
prpbably been adjusted up the fuel pressure regulator to cope with bleed backwards at the fuel pump.
should be 28 as suggested by other posters for a D jet.