GX690 comet TW 8036 pump acting up

Has anyone had their machine act like an automatic weapon? I’m thinking its an unloader issue but im not sure how to confirm. Pressure seams to go up and down a little also. I’m not really sure how else to explain…

Can you attach a video of it. Could be cavitation from low water or maybe an issue with the bypass. Is it a new setup?


I will get a video up, its got about 110 hours on it now.

Sounds like air in the system… Check for leaks! It could be that it’s sucking air in somewhere

The pulsating can be felt the most in the line going from pump to unloader and the line going from unloader to water tank while in bypass. I also unhooked the bypass back to the tank and noticed there is no flow when I pull the trigger using a lower pressure tip. Water is not pulsating out of the unloader when on the trigger.

Also, I checked the in flow and do not think it is pulling air or has inadequate flow.

Without having any water trickling out of the bypass when you’re on the trigger you need to adjust the unloader. Although, it’s probably not the cause of your problem. To adjust the unloader put a nozzle on that gets you the specs of your machine. Squeeze the gun and turn the unloader until just a trickle of water comes out of bypass.

I would throw a new unloader on for the pulsating. I think it’ll fix it but, if anything, at least you’ll be able to eliminate it as the issue.

I disconnected the hose from the pump where it enters the unloader. There is heavy pulsating coming straight out of the pump.

Belt slippage


Is this a sign of belt slippage?

Looks like @Redjess is correct. That’s a lot of belt dust.

Do you think I would be able to see it slip while it running?

Its slipping for sure… I just saw the pic and thats alot of rubber dust

Just check the tension. That’s part of regular maintenance so they’re probably due anyways. It definitely needs done. Look the belts over good too. They might need replaced due to the wear caused from slipping.

@Newguyohio that braided supply hose going to the pump can collapse when sitting in direct sunlight. Consider non-collapsing hose

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Should water come out of the inlet in the video?


Nice find! I think you found the issue. When rebuilding a pump you can test the valves by blowing or sucking and no air should get through. Is it still under warranty? I’d go ahead and replace the valve and put in back into service. I’d maybe consider just doing them all while you have it off. Although, 110 hours isn’t much. Pull the valve out and inspect it. They can be tricky to get out with the proper valve removing. I usually use two 90 picks with the ends ground down enough to fit right. Insert with the picks facing opposite and pull up. Be careful not to scratch the cylinder up where the o-ring makes contact.


For anyone that is interested, I confirmed it is a bad check valve.

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Nice work! Make sure the spring isn’t stuck down line somewhere. I’m not sure where the path from that valve goes but you don’t want that spring tearing anything else up. I’d definitely try and find the spring if it popped out or do a little more digging in the pump just to make sure.