Hi guys
I have a hot water machine with an unknown spec pump that I just rebuilt (put a new piston in it). Pistons are 15mm. I have unloader set to 3000psi just to be safe, but thinking it might be rated for more. How can I test it to find out what it should be doing? Engine is a 12hp.
Thanks
That’s a slick little unit. Should be specs listed on the pump. 3000 is not a safe number to start at if you really don’t know the specs. It’s likely fine but that could be a 2500psi pump and you’re already overloading it and then when you let off the spike will really punish it.
Ooh, I just looked at the pics closer and you have a built in unloader and that outlet off it is not ideal.
That thing is cool who made it
As you can see, no name plate on the pump. It is a Chinese pump, I have no known specs on it at all, thus my question about finding out what pressure to run it at. Also what makes you say the outlet from the unloader is not ideal? What is the ideal way to do it?
Not sure, the only info I have is the name on the machine, “Precision Pressure”. I think they’re bankrupt now. It must have been just a company who threw these machines together. It’s actually kind of a pain in the ■■■in that the burner and ignitor are 220V. To fix that issue, they installed a 220V inverter on the machine. To solve that issue, they installed an alternator to be able to put out enough power. To solve that issue they installed a dual shaft pump (impossible to find parts for) that has the extra pulley on the end to run the alternator. In the end I’m not super stoked about the machine but I got it for cheap and it makes hot water.
And yes I have contacted Unimanix to ask them about the machine, they have no clue what it is, said one of their salesman must have just slapped a sticker on it maybe during a service.
Built in unloaders are meant to be fully open, yours had a handle at some point. That pump looks very similar to a direct drive comet pump I had on my gx390. It was a 3600psi 4gpm I believe.
Oh really? You mean screwed in all the way? I’ve never beard of that before. I changed out the spring in the unloader with another one because the original was broken in 3 pieces.
I’m confused as to what changed the pressure rating between different pumps. Comet for example will have 3 different pumps with the same bodies, but different pressure and GPM ratings. Do those have larger crankshafts etc to take more load and abuse?
Yes I believe you turn it to the right until it stops, there’s supposed to be a handle on there. Depending on the pumps rating, it’s requires a certain amount of hp to accomplish it. The higher rated pumps are larger in size.
Thanks. I just got some new 4.0 orifice tips and tried them out today. At full throttle on the 12hp GX390 I was only getting around 2400psi from the pump. I guess I need to lower the orifice size of the tips to maybe 3.0, right? I’d be happy with around 3000psi at the pump on full throttle.
Interesting. That does look very similar, but there are quite a few differences. Thanks for the link, though. I’ll send them a picture of my unit asking if it’s one of theirs.
EDIT: They just replied, nope, not one of their units.
I’d stay a with the 2400 PSI if it was me.
Why? That pump is definitely rated for more than 2400psi why not get the right nozzles?
Is the unloader fully open?
Not fully open. If I turn it up, when I let off the gun, the pressure will spike too high (like 5-6000 psi). Right now I have it set so it spikes around 3500psi.
I took it as he had the pump set correctly and the nozzles were giving him 2400psi which is good for concrete. I had a super long day and it’s entirely possible I read that wrong.
Long day washing I hope lol
Heath hasn’t been himself all day, I haven’t seen a single link posted. Look after yourself heath 
I’m kind of at a loss here on what to do. I have a feeling my unloader isn’t working correctly. When I turn the unloader in (more spring pressure), it raises the trigger-on pressure slightly, but has a large effect on the trigger-off bypass pressure.
Think I should change the tips for some 3.0’s?
