My pressure pro 5.6 gpm 2500 psi cold portable is pulsing when I pull the trigger. I noticed this last week when I was not hooked up to a supply tank and figured it was a supply issue. I hooked up to a 65 gallon supply and still getting the pulsing when I pull the trigger. I have looked at the check valves and they appear fine, so do the o-rings. The oil is not milky but I am changing it because it needs to be done anyway. I am also replacing the air filter. Any suggestions? Russ Johnson, I know you gave me a couple of possibilities on Friday but I have had a lot on my plate and was not able to get to fixing my pressure washer till now. Unfortunately I failed to write anything you said down and I have forgotten what you told me.