trying to start 2003 volvo ved12
 

Changed the secondary fuel filter, filled new one with fuel, then the priming process. This truck has the priming pump on top of the filter assembly. There is a vent valve that will let out pressure when I loosen it. Am I supposed to repeatedly let this pressure out until fuel comes out? There is also another vent on the driver side of the engine which fuel comes out when loosened. This isn't the first time I've had trouble with this, just the first time I thought I'd ask.