If it is dribbling out the end your valve needs to be rebuilt or replaced.
If you are going to replace it, replace it with the all metal valve from spraying systems. All the plastic ones I have seen are junk especially the ones that have stamped right on them 150 degrees. Even a wimpy truckmount will exceed 150 degrees while putting down prespray and make those dribble after a week. Can't believe they sell those for truckmount applications.