General Pump ZK1 Unloader

[Power Clean 14]

Ok. My Pulsar 280 unloader just died. It will no longer bypass when the trigger is released and it’s putting the engine under a load and spiking the pressure on my pump. I have disassembled it and found no obstructions and/or damaged check balls or springs. It may just be worn out. I really don’t know (over 500 hours and 2 years worth of ownership). After reassembly, it still will not work. I have been reading every post I could find on unloaders from 3 different BBS sites and really haven’t found much on this particular unloader from GP. I’m replacing the 280 with a ZK-1. My machine is rated for 3500PSI so I didn’t go the K7 route. Anyone with experience on these unloaders? Can I use the pressure gauge on the pump at the discharge outlet to set pressure or do I need to tap into a port on the unloader itself? Will my current pressure switch work correctly with this type of unloader or will I need to change something. Will it plumb the same as the 280? I have a Delco RK-41XP with the bypass currently plumbed with a 3/8 hose into my tank.

[BigPete 14]

I have them and they work fine for me. They plumb like any unloader.. Out goes to gun, in comes from pump, bypass goes to bypass.

[Jimmy M 14]

I have the rk 43 from delco,It came with the ZK1 unloader. I would think everything should plumb the same as your old unloader.

[Power Clean 14]

I have the rk 43 from delco,It came with the ZK1 unloader. I would think everything should plumb the same as your old unloader.

Okay, great. Thanks guys. Jimmy, if you don't mind could you send me a photo of yours?

[One Tough Pressure 580]

I use the Zk1 and like it very much. I was using K-7's but they kept failing way to soon.

The only thing that will be noticably different than most unloaders is that when adjusting the pressure, you crank the nut counter clockwise rather than clockwise.

I bypass to the tank, but also have a three way ball valve to return the bypass to the pump, so that I can upstream without filling my tank with chems.

http://www.generalpump.com/PDFs/ZK1-Unloader.pdf#search='zk1'

[Power Clean 14]

I use the Zk1 and like it very much. I was using K-7's but they kept failing way to soon.

The only thing that will be noticably different than most unloaders is that when adjusting the pressure, you crank the nut counter clockwise rather than clockwise.

I bypass to the tank, but also have a three way ball valve to return the bypass to the pump, so that I can upstream without filling my tank with chems.

http://www.generalpump.com/PDFs/ZK1-Unloader.pdf#search='zk1'

I see the ZK1 has a 1/2 in. bypass port. I'm currently running a 3/8 in. line back to the tank and I do not use a 3-way valve because I do not run chems through the pump. Do I need to move it up to a 1/2 bypass line? Another thing that came to mind, from time to time my hoses do get run over, but I nevered worried that much about it because the lines stayed pressured up with the old unloader. Now that this unloader will relieve the pressure of the lines, will my hoses be more prone to damage from being run over at the drive thru?

[One Tough Pressure 580]

I reduced the 1/2" bypass down to 3/8" to use the line I already had installed. The bypass is lower pressure and no more volume than the pressure side. However if it makes you feel better then up to the 1/2"

I get my hoses run over frequently, and have not had any problems. Car tires are not so bad, but big trucks and solid fork lift wheels will do some damage.

[BigPete 14]

You may need to downsize to get it to work properly - I have 1/4 inch hose on my bypass. 3/8" would cause the unloader to cycle in and out. Have had no problems since going to 1/4".

[Power Clean 14]

Thanks for all the help guys. I will try the current bypass setup as is. If I have trouble, I will go another route.

[Jimmy M 14]

Greald ,sorry I can't send a picture right now ,camera is on the blink and I'm not sure how to do a picture send. I also had to go with the 1/4" bypass hose to keep machine from cycling .

[Power Clean 14]

Well, I'm curious. If this unloader relieves pressure off the hose and pump when you release the trigger then most of it must go to bypass, right? So I was wondering how the 1/4 line handles that. Obviously it does, can someone elaborate a little?

[One Tough Pressure 580]

Well, I'm curious. If this unloader relieves pressure off the hose and pump when you release the trigger then most of it must go to bypass, right? So I was wondering how the 1/4 line handles that. Obviously it does, can someone elaborate a little?

It is a 1/4" line but with no tip for a restriction. It would be the same as if you ran an open gun with no tip.

[Power Clean 14]

It is a 1/4" line but with no tip for a restriction. It would be the same as if you ran an open gun with no tip.

True, makes sense and I should have realized that myself. Thanks Alan. It's been one of those days.