Ok I have a sermac 37Z having problems. This is the first experiance witht he Sermac I am a Schwing guy.

You can pump fine with the thing butabout every other truck or so it will do like soft plug. You can be going balls to the wall and it will still do it. You can back strok for a second and role on. Anyone have I deas on this one? Yes I have been working with sermac just have not found the problem as of yet.

Just a few things that have4 been done and checked. The bars are fine, Cylinder reliefs set and adjusted several times to see if any change. After going through everything and playing with it there has been alot of improvement. When I first got  here the truck would plug a couple times a truck BUT like I said its not a hard plug just backstroke for a mili sec and carry on.

Hopefully at that makes sense to someone.

Also on a side not last two weeks have had a problem with the volume control. Its not in the fuse, bars are moving between 10-26.

Thanks for any help

ZO

I havent spent alot of time with the sermacs but i have operated them , sounds to me like your wear ring and wear plate need looking at , when there not right you will get these problems because the water is being pushed back into the hopper leaving dry lumps in the tube , when you suck back it pulls the lumps back into the hopper alowing the auger to mix it back up and keep pumping , try putting a straight edge over your wear plate its a pretty good way to see if its in need of repacment

had a lot of experience on sermacs , try taking the magnetic solonoids of the top of the main valve block .and clean them up the some times get rusty. also the pressure taps for the change over rams some times work there way out resulting in more pressue to one ram than the other.this will cause it to go in to phaze thinking that it is block when it isnt. it take some real routh concrete to block a sermac in the s valve

volume control will more than likely be the output valve sticking , should be mounted under the hyd tank but follow the small feeder pipes from the main pump to a small hyd. block with a small solenoid mounted on it, just take it apart and clean it out. how old is the pump?  may need hyd oil changing ? other than this it could be the control card in the rear box. looks like a credit card. 

Blockage sensation could be either wear plates or slow solenoid on the valve block.

Thanks Guys I will try and let you know busy for the next few days so may be next week.

I have checked Magnetic switch on the valves they seem fine and it does this in soft and hard mode. I have set the relief valves  several times to adjusted stock to the way our other sermac is set etc. I have brought this along way were the truck can be used but not perfect yet.