OT John Blue spray pump

I have a sprayer with a John Blue ground driven pump. I have used this for about 7 years with no problems. I used it two weeks ago to spray 25 acers. It has always had good pressure/flow. While trying to spray nitrogen today the spayer just up and quit spraying. I have taken the output line loose three times: the firt time from the top of the pump. I had low flow. The second time I took the output line loose from the junction box and I did not have any flow. The third time from the pump again but this time with no flow. I then took the supply line loose from the pump. I had plenty of flow going to the pump. I had my wife hold her hand on the input of the pump while I turned the pump by hand: she said there was no suction.

Having said all of this has anyone had any experiance rebuilding one of these pumps? Is it a do it yourself or seek professional help? Is there a quick fix or is it a major rebuild?

Any suggestions are appreciatted.

CDS-JOHN BLUE 1 800 253 2583.

Huntsville Ala

not knowing with one you have i'm assuming it's one of the older models without all the electronics, first make sure the sprocket clutch is driving the pump shaft and the adjustment hasn't slipped out of adjustment or the key in the shaft that drives the adjustment lever isn't sheared or missing, if the shaft is working ok remove the 2 long bolts that hold the housings to the pump that the hoses connect to ,the housing can then be removed exposing the check valves, check them for broken springs or parts ,also you can see the pump piston, rotate the pump and see if the piston moves ,if it doesn't move and the adjustment hasn't slipped something has broke or come loose inside the pump ,the piston has seals inside the cyl. barrel if they wear out generally it's hard to prime and you loose pressure, but in my experience not completely there are 4 bolts that hold the cly. barrel to the crankcase when removed the barrel can be slid off the piston exposing the piston seals, isn't complicated to rebuild even a complete rebuild of the crankcase,a piston seal kit cost aprox.85 dollars most all the ones iv'e talked to that had pumps rebuilt said it cost them from 700 to 800 dollars , i put a seal kit, connecting rod ,bearings and shaft seals in mine for less than 200 a couple years ago sounds to me like someone was making a good profit

Thank you GBS. That is the kind of information I am looking for. It will be next week, but I will crack it open and see if what you have described is what has happened.

JWalker