Airless Sprayer with no suction

[BradSP65]

I'm in need of some assistence to understand how an airless sprayer actually works. I have an OldFields 600 EL which has no suction and will not prime. It appears to be very similar to all the models below as the parts are interchangeable. I believe that these are all manuafactured by Seiwa and half way down the page give an idea as to how these work.

http://www.seiwa.com/wp/us/home/

Appears that they are still selling these as here.

http://www.seiwa.com/wp/us/products/sp-60l/

Spraychief- 4500s
Oldfields- EL60/ Super60
Seiwa- S600EL/700GE
Novaspray-Exceed 60
Atomex- GM60E/GM70G/LM70G

I'm at a loss as to how these diaphragm pumps actually work and function. From information I have gained the common issues are the diaphragm is blocked with paint and/or the inlet or outlet valve is bad. I've taken the head off the machine and cleaned out the diaphragm area. The diaphragm is rather rigid and I was expecting it to be flexible but its not. Its still intact and not broken etc. The inlet and outlet valves to my uninformed eye appear to be working. Although there is some rust on the inlet valve it still holds fluid (when not turned on) and similarly with the outlet valve. Both hold fluid in the off state which to myself means that the seats are still good and not leaking.

So now I'm at a loss. When it is turned on there is very minimal pressure and if fed with water it dribbles out the spray gun. I don;t understand how the hydraulic pressure valve plays a part in the operation with the diaphragm. I'm suspecting that potentially this is where my problem my be.

Does any one here have any knowledge that could assist? Thanks.

[BradSP65]

Looking at the Seiwa site and the fact that the hydraulic fluid should be used to transfer pressure to the diaphragm I started thinking that perhaps the pressure valve is not working and releasing all the oil back to the tank. So I thought to take the head off and fill the well with oil, reattach the head with the pressure valve at maximum pressure. The thought was after running to then take the head back off again and see if the hydraulic oil was still in the well. After this process, there was no hydraulic oil in the well. Initially, I just thought oh the valve is the problem but then thought o placing the oil in the well and see if it is held there. It does slowly leak away through the piston after 3-4 minutes. which is probably shorter than my time to get the head on and off and tightened. The Seiwa site states.

"No wear down in the sliding pump, the sliding part (piston and cylinder) in the hydraulic pump is always in oiled state making it highly durable and no maintenance is required."

So I am thinking that this is probably correct rather than incorrect behaviour. I have no real way of telling.

However, I tightened down the lower assembly while the head was off, thinking if I turn it on very briefly that there should be hydraulic oil pumped into the well somehow. Now there is no oil pumped into the well and I am actually at a loss as to how the oil gets into the well to start with. Anyone with any ideas?

[bgsengine]

No ideas really - only airless sprayers I am familiar with are the TTI/Ryobi/Milwaukee ones, and even then, only ever had two of them to work on.. never even heard of Seiwa til now.. I rather doubt most of the folks on this forum are too much into that sort of product, unless there's some that are powered by small engines (rather doubtful as they could not be run indoors, and if you were going to do engine powered, might as well just run an air compressor off the engine instead..)

[BradSP65]

Thanks for the response. Yes I understand that the electric engine driving this may not be seen by many but still thought that perhaps some one would have more knowledge than myself on how the hydraulics interwork with the engine and the cam to drive the pressure on the diaphragm. I'll keep plugging away trying to determine how this is works. However thanks for the input.

[BradSP65]

Well I have managed to fix my unit. For anyone else searching my issues is the pressure control valve. Replaced it and now everything is fine.