Fuel Pressure Regulator

Connect a fuel pressure gauge between fuel line and fuel injection manifold.
On 240 and 240 DL, remove panel under right side of instrument panel. Disconnect fuel system relay connector. See Fig 1 .
On all models except 240 and 240 DL, remove fuel system relay. Fuel system relay is located in fuse/relay box. See Fig 1 .
On all models, energize fuel pump. Connect a jumper wire between terminal No. 30 and No. 87/2. Observe fuel pressure reading. Fuel pressure should read 42 psi (2.0 kg/cm² ). If pressure is too low, pinch off fuel return line and recheck pressure.
CAUTION: DO NOT allow pressure to exceed 84 psi (5.9 kg/cm² ).
If pressure rises quickly, fuel pump and lines are functioning correctly. Replace pressure regulator and recheck pressure. If fuel pressure rises slowly, fuel filters or lines are blocked. If pressure does not rise, fuel pump is defective.

Fig 1: Identifying Fuel System Relay Locations & Terminals
Courtesy of VOLVO CARS OF NORTH AMERICA.
If fuel pressure is high, disconnect fuel return line from pressure regulator and blow into line. If line is open, pressure regulator is defective and should be replaced.
Pressure may also be checked with engine off and fuel gauge connected. Attach a hand-held vacuum pump to pressure regulator. Line pressure should decrease as vacuum is applied to regulator.