I recently acquired a Graco HVLP 4900 procomp in non-working condition. I have completed the rebuild of the unit and everything works great now…but one little issue. I am getting a leak on the gun at what I believe is called the “Packing Nut”. It where is the needle goes into the front part of the gun in front of the trigger.
I did perform a rebuild of the gun – did I install the parts incorrectly? What would cause it to leak here and what should I try?
The packing material in Graco guns typically consists of 5 plastic washers and a brass nut. The brass nut is adjustable, and controls the amount of drag on the fluid set (needle).
when you rebuilt the gun did you dis-assemble the packing and replace it? If not, you may just need to tighten down the brass nut a bit to take up the gap around the fluid set. Otherwise the old packing may be shot and need replacement. It's a pain to replace because there's 5 tiny plastic washers that are grooved and all have to fit together in the right direction.