CAT 310 pulsating, but not all the normal problems.

[lighthousecarwash]

Guys, I'm pulling my hair out with a CAT 310 pump this week. I just renovated a wash and went through the pump stand and replaced all the leaking fittings and replumbed everything to the holding tanks and the city water. 1 out of the 4 pumps was pulsating like crazy. I pulled all the valves and they were a disaster. I replaced all 6 of the valves and inspected the head to ensure that the sleeves were not washed out. Put it back together and it's the same thing. I pulled the head and replaced all the low pressure seals and put it back together again. Now when it's on rinse, it works fine. No pulses at all. As soon as I switch to wax or soap, it starts pulsating again, and pretty bad. I removed the hose from the wax/soap solenoids and put a plug in the side of the pump to eliminate any air issues, but it still does it. As soon as I switch back to rinse, it quiets down and runs fine. I have checked the cold water valve and the check valve and they all seem to be working correctly. The only thing that has me nervous is that I lowered the soap/wax tanks and they are now lower than the top 2 pumps, but the very top pump does not have this same problem. I don't know if something is not allowing the pump to create suction and draw the water in, or if it matters. Does anyone have any ideas?

Thanks,
Lighthouse

 

[2Biz]

You didn't mention what water supply you have for Soap and Wax. Is it hot water? If so, sounds like the solenoid that switches from cold to hot isn't working right and not allowing hot water to make it to the pump. Do you have both hot/cold float tanks or city pressure for both, or hybrid? City pressure for cold, float tank for hot. Or is it possible you have a valve closed on the hot water supply to the affected pump? Some stands, like my old one, have metering valves that help create a vacuum to draw soap and wax. I had gate valves in my old setup and one of the stems broke off and stuck closed. The pump did the same thing as yours when switched to hot....Needless to say, I did away with all that crap! No more water flow metering valves on each of the supplies to the pump. 1/2" water supply tubing is all that's necessary to create enough vacuum to draw soap and wax efficiently. Although my wax/soap tanks are above pump level....Amazing how much over kill there is in some pump stands...

 

[mrfixit]

Yeah sounds like hot water valve sticking would be the first thought. Or air sucking in between the hot solenoid and inlet.

 

[lighthousecarwash]

I have city pressure on the cold and wax/soap is hot in the holding tank. Pump will have to suck to draw the hot water. My soap and wax valves no longer have needle valves as I eliminated all of that. So when switching to the hot, it draws from the hot tank and either the wax or soap tank depending on which function it's on. My thought was the cold water valve is not doing what it's supposed to but I tore it all a part and it looks good. Guess I can replace it and see if that makes any difference.

Lighthouse

 

[mrfixit]

Oh your drawing straight from holding tank for hot. There has to be a solenoid right.

Sounds like maybe the line from the tank for that pump could be sucking air in one of the fittings.. Causing it to not draw fluid.... Or its got an air pocket stuck in the hose but don't think that would be ongoing.

Cold water valve sounds fine, i would focus on the hot side.

Good luck!

 

[Jeff_L]

Would take some work, but you want to find the issue. Understand the differences between the two functions and start eliminating things. Such as turn the cold valve on for hot, see if it still happens. Are you using a zero pressure regulator? Perhaps that has gon bad.

 

[cantbreak80]

With a pressure fed cold water system, there has to be a check valve on the hot water feed to prevent cold water flow into the tank.
Maybe that check valve is stuck or installed backwards?

With the system idle, disconnect the hot water supply hose at the pump and view the volume of water. If it’s determined to be sufficient, inspect the hose and fittings. The hose may be collapsing inside when subjected to pump suction.

Temporarily connect the hot supply from an adjacent pump. Does that resolve the issue?

 

[MEP001]

Pull the manifold off and make sure none of the pistons are loose where you can move them in and out by hand. I was working on a pump that was smooth only on rinse, and found the rod cap bolts had worked loose. The rinse pressure was pushing the piston against the crankshaft and on soap/wax it had a "dead cylinder."

 

[mrfixit]

Good idea, no incoming pressure to keep it tight.