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Slight Pulsation In Bay...PUMP?

W

wASHN4FUN

New member
I recently bought an OLD SS that only had one out of six bays working. Slowly, but surely I have been learning, and renovating by myself. My last bay to get working had to have everything from the controls to the pump accessories replaced, to finally get it working. At first it hammered really bad...but after reading through all of the posts on here I took action to replace valves. Now it only has a slight pulsation.?! I checked thoroughly for cavitation, but could not find any (major) signs of it....
I have never been in this business before and have learned as I go. Being a Master Auto Technician has given me an advantage in not having to pay someone else to do the work....but am far from prideful. I know that I still know nothing, and appreciate ANY help. Thank you in advance!
 
You don't say what brand/model pump it is so I will assume a Cat 310 or 5CP. If replacing the valves helped it leads me to believe the o-ring may have been broken and washed out the head. A new o-ring will take up some of the gap along with some pulsation until the new o-ring fails. Was the head washed out? How about the seals? Did you remove or replace them? The head can wash out in both the valve areas and seal area.
 
Read the "sticky" thread near the top of the General section of this forum. It will help you identify a washed-out manifold.
 
Can you see the pulsation at the gun or are you just hearing a vibration coming from the attic? I have a slight vibration in bay 3 that resonates from the attic. It gets a little worse when you let off the gun...My system, Mark VII came out with Pulsation Dampeners when new. But I only have one left in service. I've since replaced the damperners with a short piece of HP line capped off. Seems to work ok....But don't know how you can get rid of the pulsation completely because of how our pumps work.

So more information will help get this resolved for you.
 
First thing I would check would be if the pump was being starved for water. Some systems require the pumps to be choked back for them to pull chemicals. If choked back too far it will cause pulsation and could damage pumps. You can also check filter's in line that feeds the pump.
 
Etowah
O.K. I have cat pumps and they all match (4). I have tried adjusting regulators to eliminate the pulsation....nothing changes. You can feel it at the trigger. It is nowhere near as bad as it was, before, but it can't be right.
 
Did you check the feed tank or lines to your pumps? Filtered clogged? Hose collapsed? Water getting to pumps. This sounds like the pumps are starving for water. This will cause pulsation all the way to the bays.
 
Are you running weep guns? What kind of regulator/unloader are you running? Pictures help...
 
A pump pulsating is much more likely to be a problem with the pump than with anything else. Adjusting a regulator will never solve a pulsation issue unless there's something fundamentally wrong with the way the plumbing is set up.

Did you ever check the pump seals?
 
I'll bet you've got a seal problem or a washed out head. Have you taken the pump head off and removed the seals and inspected the seal seating surfaces.

Here's a picture of what a Cat 310 head out looks like when they get washed out. Notice the groove cut into seating surface that the seal sits in. This will give you an idea of what to look for.
 
like I.B. said earlier, look at the orings on the old valves. If they are split or missing, you have washout. You can also check the outside of the high pressure seal to look for grooves worn into the seal, another sign of washout. I know alot of operators replace valves when in fact valves rarely go bad, they usually get damaged by something going through the pump. Putting new valves into a washed head is wasting money, you need to have the pump re-sleeved. Take a flashlight and shine it down the valve ports, take a small screwdriver and run it around the seat, you will feel it "catch" on the washed out areas. Some washout is bad enough to see easily, others is not.
 
Thank you for all the advise. I have another head at my shop that looks good. I think I will take it to the wash and put the new valves in it & see what happens, before I decide what to do next, if anything.
 
I've heard it said that the arimitsu pumps are the way to go when you start running into major repairs.......what is the general census on that?
 
A couple of possibilities if the pump is sound:

Since most carwash pumps are gravity fed, there is a ever-so-slight chance that an air bubble is trapped in the head.

Turn the pump on and CAREFULLY loosen the discharge fitting at the pump head. It will get you and the surroundings wet so be prepared. A trapped air bubble will have an escape point by doing this.

Or, if you don't want to get wet, simply install a spare hose on the pump's outlet, bypassing all of the downstream components. Direct the hose to a drain or back to your rinse water tank and turn it on for 10 seconds or so. (Without a trigger gun and spray tip there's no high pressure so don't worry about blasting water coming out of the temporary hose.) Reconnect the plumbing and see if it still pulsates.

One more thing to check is air leaks into the inlet plumbing...I know, you'd think an air leak would also show up as a liquid leak...but that's not always so.

I've had soap and wax fittings leak ever so slightly...enough to cause pulsation.

A relatively easy test is to remove all the inlet plumbing and install a pressure-fed supply hose (Garden Hose).

Tie-wrap the trigger gun OPEN and secure it to the wand holder during this test! DO NOT FAIL TO DO THIS! A deadheaded positive displacement pump can do some serious damage when it's head blows off! And, an open spray gun will flail about the bay like a crazed shark in a man-eating contest!

Turn on the water, then the pump. Still pulsating?

YES? Pump issues as stated in the previous replies.
NO? Look for inlet leaks in your Soap/Wax system and by-pass plumbing.
 
Since it has been a while since the OP posted I might hijack this thread...;)

I've had a bit of a starving pump. The pump just sounded a bit different than the others. However, as soon as I wanted to investigate it the problem disappeared :confused: Could this be an air lock that has gone now?
 
You might have a check valve that's hanging intermittently. I've seen that a lot with the 1/2" SMC valves.
 
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