Unloader failing?

I use the ZK1 flow sensing in loader. Replaced it just back in October of last year. A couple of questions everything is related, but here is the background. I bought a sludge sucker a few years back, and when I first started using it, it worked great. I’m was and still am using 8gpm and the sludge sucker worked just fine several times. Last fall I tried to use it again and what would happen that time is it would turn on for a second and then it would cut out, it would cycle like this repeatedly, basically making the thing useless. It had been a while since I used it so I thought maybe the tip was clogged, but it was not. So then I started thinking that maybe the tip was too small for 8 gallons per minute. I went to try and change out the tip, but access was impossible. I gave up and quit using it. Not too long after I ended up replacing the unloader, because there were some other issues going on with it. A month later I tried to use the sludge sucker again (after I changed the unloader) and it worked.

Similarly when I was at Northbay Equipment getting my pressure washer serviced, I talk to the mechanic about using a smaller tip to get the water hotter than the 175° I could reach max with my standard 9.0 orfice tip. I found a 3.5 tip in the truck from my old machine a really long time ago and we tested it to see how hot I can get the water by reducing the flow and I was able to get it up above boiling, almost 220°. I asked him if using such a small tip once in a while to get the water super hot to remove oil stains would cause problems with the machine. He said he would recommend going no lower than 5.5, but either way the rest of the water would flow back through the bypass. When we tested the 3.5 to see how hot it would get, it did not cut out and it worked fine for several minutes. Then about two weeks later, my tech accidentally ended up putting the same 3.5 tip on the gun and it was doing the same thing as the sludge sucker was doing. Turning on for a second and then cycling off. Here are my two questions.

  1. Is the cycling problem with using smaller tips, including the one in the sludge sucker, an indicator that the unloader is failing?

  2. Would using a 3.5 or 5.5 tip on an 8 GPM to get the heat up, cause problems with the unloader or the pump, or would the bypass negate any issues from using too small of a tip to get super high heat or to use the sludge sucker that I cannot change the tip on?

I’m thinking my unloader is going bad since both the sludge sucker and using a smaller tip to get higher heat no longer work like they did, working constantly without cycling…

Maybe @dperez and/or @Firefighter4hire might know best as they seem to be the experts in all mechanicals of these machines.

You have to HAVE TO nozzle the sludge sucker for YOUR machine. You have to nozzle EVERYTHING for your particular machine.

Just because it worked or didn’t work at some point is neither here nor there. Unloaders are loaded with springs that have a higher rate when new and less when old.

You don’t nozzle down a gun with a flow unloader unless you want it to short cycle. Sometimes it may and sometimes it won’t. Who knows it’s your machine and YOU should know it. That’s why you’re testing right?

Everything you’re trying to do here can be accomplished with a pressure actuated unloader.

Has far as your sludge sucker goes you have to use a socket and extension to remove the tip. Going through the the discharge of the sludge sucker.

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Honestly, I tried to do it in the field when I was at a job an hour away from the shop and that was before I had a complete socket set on the truck. I will change that out before I use it next time. Thank you for the tip!

Thanks man I will definitely change the nozzle to the proper one. I’m wondering though, I don’t plan on using a 3.5, but probably a 5.5 to get that higher heat once in a great while to deal with really bad oil stains. The funny thing is I thought the 3.5 was going to make the pressure incredibly higher. After 200 feet of hose it only changed it from my standard 2400 psi at the gun to 2700 psi. This is why I thought it might be safe to use it sometimes to get the higher heat. I bought a new unloader and will swap it out. It’s the same one so it’s flow sensing not pressure trapping, but if it does not cycle, then do you think it is safe to use the 5.5 instead of the 9.0 once in a while for the higher heat? Or do you think it will prematurely wear out the unloader? Or cause strain on the pump? The unloader wearing out isn’t really a concern because I get them from the 96 bucks at KleenRite Corp. But I definitely don’t want to mess up the pump. My thought was that if all it did was send the excess water I couldn’t fit through the smaller hole back through the bypass that it would be safe for the pump. I’m not sure if that’s true though?

If it cycles add some bolt turn. On a ZK1 that’s CCW. You won’t strain the pump but the manifold does sees back pressure. If you have a 3500 pump you’re already getting very close to cracking it. Put a gauge as close to the pump as possible and get your psi from there. You won’t prematurely wear out the unloader by choosing to nozzle down. Just hope you know this isn’t the correct way to do it :wink: