drivers side rocker arm assembly getting no oil

I have checked all the basic things but the oil passage that is at the center bolt on the rocker arm assembly does not flow oil through it when the engine is running. the pass side flows oil through the little port holes to lube the push rods and the rocker arm itsself.
do you think I need to pull off the head and check the oil passages or do I have a pump problem????



HELP????