Stihl SG 20 Backpack sprayer - unable to pressurize !!! NEED HELP

   / Stihl SG 20 Backpack sprayer - unable to pressurize !!! NEED HELP #1  

pharmvet

Platinum Member
Joined
Sep 28, 2008
Messages
535
Location
North East TX
Tractor
Ford 7710 II FWA, NH TB110 FWA w/ NH 46LB loader, JD 5303 2wd w/ loader
I have a Stihl SG 20 backpack sprayer that I purchased last year. I used it all last year and this year up until now. I have been very careful to wash it out and de-pressurize after each use. I have also been conscious about oiling the pump piston. Yesterday I filled it up with water / roundup mix, strapped it on my back and set off to spray my yard perimeter. To my utter disgust, I could not pump up any pressure (very little) I pumped and pumped and pumped, but could not get pressure. I called my dealer and asked about common problems so I would know where to start but got no help. After some reading (interned and instruction manuel, I cleaned the filter in the hand wand (It did in fact need cleaning). Still unable to pressurize. Then I took the piston out of the pump and examined it (lots of oil, but no apparent problems). I then opened the chamber housing the ball bearing (no apparent problems). I cleaned meticulously and put her all back together (no improvement) The only thing I noticed is that there is lots of cracking in the hose where it bends. However, there are no leaks. Could it be possible that the cracks are allowing air to escape (and thus I cannot get pressure?) while not allowing water leaks ?? I tend to think no.

Has anyone else experienced this problem? What would you suggest I try next? thanks.
 
   / Stihl SG 20 Backpack sprayer - unable to pressurize !!! NEED HELP #2  
I have the exact same problem with my Stihil G20 sprayer. Did you ever find out what prevented your sprayer from building up pressure when pumping. I have also checked and cleaned everything, but the hand pump fails to build up any pressure. I have also tried changing the pump o-ring with no success.
 
   / Stihl SG 20 Backpack sprayer - unable to pressurize !!! NEED HELP #3  
There are two check valves that may have deposits on them. For the first one unscrew the fitting where the hose comes from the tank to the bottom of the pump. When you remove the fitting you will find a steel ball clean it and the seat where it sits with steel wool and replace.
If this does not fix the problem check the one on the side of the pump tube toward the bottom. There is a brass cap you can loosen with a cresent wrench and there you will find another steel ball and you will need to clean it as well. Hope this helps.:)
 
   / Stihl SG 20 Backpack sprayer - unable to pressurize !!! NEED HELP #4  
I just started experiencing the same problem. i purchased a new sg20 on may 1st, it sat in my shop until I attempted to use it yesterday. It would not pressurize the chamber at all. I took it back to the dealer. They gave me a new one and some BS about it being a fluke. Got it home and ran 1.5-2 gallons of spray through it and it quit again. I again ran it back to the dealer. According to them the o-rings that seal the pump pressure chamber are drying out which is causing from cracks which allows all the air to escape. I,m on my 3 rd one in 2 days and will try using it this am. Otherwise I will head to Wilco, or dells or the local farm store and by the $50.00 which has worked fine for the last 3 years.
 
   / Stihl SG 20 Backpack sprayer - unable to pressurize !!! NEED HELP #5  
I removed the two check valves. Wiped the steel balls and inside with a paper towel. I then sprayed lubricating oil in the ball hole. put it back together and so far it works like new
 
   / Stihl SG 20 Backpack sprayer - unable to pressurize !!! NEED HELP #6  
I had the exact problem with my sg 20 but my problem was intermittent sometimes it would build pressure but most of the time it would not. The problem was the brass ball in the hose from the tank to the pump. The ball looked good, but it would get hung up and not fall into the seat. I dissembled the assembly and cleaned the area where the ball set and now it works fine. The first thing I did was to replace the piston in the pump which obviously was not the issue. Once I read this blog and fixed the problem, I went to the Stihl website and posed the same question to one of their technicians. I told him the issue and what I had replaced and did he have any suggestions. He said without seeing the unit he had no idea and I should take it to a Stihl dealer. I think he knew exactly what the issue was, Stihl really protects their dealers. You cannot buy parts on line and very difficult to even find a parts breakdown of the device in question. This is my only gripe with Stihl.
 
 
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