Has to be one of the all time simplest engines for injector replacement. There are three 10mm bolts on the fuel rail to remove. Unplug the 4 injector connectors and, starting at the front, gently pull the rail and injectors as a unit out of the manifold. I've seen folks actually bend the fuel rail doing this but has not been an issue for me. It's best to replace the o-rings top and bottom to assure no leaks but often this step is overlooked. Depends on whether you want a car-b-q or not. The injectors are held into the rail with c clips. A small screwdriver gets them lose in no time. It's fairly difficult to mix up the injector connector wires but doesn't matter as the Volvo has a batch fire setup. When replacing the rail and retaining bolts, be sure to re-install the ground wires previously held on to the injector rail by the bolts or the car won't run.
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When Volvos are outlawed, only outlaws will have Volvos!!