K9 unloader not unloading

[john@AEC 37]

Hi All,

I've been busy, busy, busy.... but finally have to stop for some help.

I had a new rig custom built - no expense spared! It can push 21 l/min at 5000 psi etc, so I spent up big on a K9 unloader. The K9 has been awesome, but now it's not.

The K9 has decided to cycle when the gun is closed (pressure in line all the time while bypass goes on/off/on/off...), after cycling for a while it will then stop, but there is still pressure in the line. Some-times it will even stick in bypass, while other times it actually works as it should.

I've checked for leaks - none to be found; changed guns and surface cleaners - the same for all. The tech who built it all has pulled the K9 apart - found the rubber o-ring on the main plunger was worn - this was re-placed and re-greased. I have pulled it apart and it has been all clean. I have also checked the pressure. All this and still it does what it wants - which is not what it should.

Has any-one had any experience with a K9 doing this? has any-one got any clues as to what else it could be?

I found (via search) similar problems with K7's that were fixed with a smaller by-pass/return hose, do the K9's work the same way and have the same problem? I'll try putting vise-grips around the hose tomorrow as I have a 3/4" hose.

Thanks for your thoughts.

[Scott Stone 604]

Yes, they work the same way. Try a more restrictive bypass and see what happens. Part of the change is probably due to wear.

[RMedbery 26]

Not to highjack the thread (well yeah I am) but whats the difference in K-5s, 7s and 9s?

[john@AEC 37]

Thanks Scott, I'll get the vise-grips out and try squeezing the return hose.

Cheers

[Paul Kassander 26]

Check for debris in the unloder itself, a small piece can clog a port and cause that problem. It just happened to me with a K7, I cleaned it out ant it worked fine. It was a small piece of plastic way inside the center of the unloader, you could only see it from one of the ports.

[john@AEC 37]

Thanks Scott, restricting the bypass/return hose solved the cycling problem. I put vise-grips on the hose and kept closing tighter until the cycling stopped. I tested by removing the vise-grips and as soon as they were removed the cycling resumed, and as soon as the hose was restricted again the cycling stopped. This worked all day with no problems. As a permanent solution I think I'll put a tap in the hose line so the flow can be adjusted to suit.

Thanks Paul, I've cleaned it and re-greased it (twice now) as well as replaced the worn o-ring.

And now - off to work; one large driveway (exposed aggregate) and then three boat ramps.

[Paul Kassander 26]

Go make some money!!!:D