I am having a problem with my injector valve, it won't pull and chemical. I have bought three in the last month, they will work for a while then quit. I have a 3500 psi 5.6 gpm, M-T-M . I was talking to the company that sold me the unit, and they said they have had this problem before, try moving the valve closer to the hose reel (less hose). I tried it didn't work. I have been washing for about 8 years, and only replaced the vavle 2 times. there is a problem somewhere just need a little direction. thanks