Volvo Repair: 245 fuel regulator operation, fuel pressure regulator, volvo mechanics

Question
Hello Volvo mechanics, one and all.  My '87 245 has poor gas
milage at 14 mpg . I suspect the fuel pressure regulator isn't functioning correctly thus keeping the pressure high even when it isn't supposed to be.
I understand the theory of the unit, I.E. low vaccum/high load pinches off
the return line to the tank and high vaccumm/low load would havethe valve
open some to allow less pressure and more flow returning to the tank..

Ok so I have taken off the unit and put a vaccumm pump to it and brought
it down to an idle vaccumm of 21 inches. The diaphram doesn't move , hence perhaps a reason for the rich mixture.

the question I have now is... does the diaphram/valave need the fuel pressure and the vaccumm to move it ?

The oxygen sensor works ok- it reads from .78 volts to .83 during driving- which is rich.  thanx for your time and consideration, Paul morningstar


Answer
Paul, in a word, yes.  If the regulator was bad, fuel would be spurting out of the vacuum nipple.  ECT sensor may be a culprit also by overfueling as well as a possible air mass meter on the fritz.  14 way to low.  should get at least 20 in the city and about 27-30 on the highway.  Roger