New Cat 310 running rough - any suggestions?

[Mchas]

I had an older pump that I thought was on its last legs, so I just replaced it with a brand new Cat 310 and new unloader. After hooking it all up and turning it on, it runs fairly rough. Not extremely rough but not smooth (I can compare it to the pump right next to it and it runs much smoother). And the worst part is, when the handle of the rinse gun is released, the unloader makes a pretty significant banging sound and the pressure drops for a moment. I turned the bay off for now until I can figure out what the issue is.

In trying to figure out what the difference could be between it and the other better pump, the only thing I can see different is that there is a check valve on the line out from the unloader on the good pump. Could that make a difference? I suppose I could take it off and put it on the other one and see if it helps.

Any advice is appreciated!!

 

[DiamondWash]

Did you fill the new 310 with Oil?

 

[Mchas]

Yes, I did. I also put some drops of oil in the three holes but then when I read the instructions it said to not do that at first, but it was too late. I don’t think that could be causing the problem but maybe?

 

[Mchas]

I am currently thinking that the banging of the unloader when the gun trigger is released could be because the locking nuts in the unloader are not in the right position - could that make sense? The unloader was originally not allowing me to set the pressure high enough so I took the handle off and put the locking nuts pretty far down and then put the handle back on. Thinking about it more, it’s probably best to put the nuts in the position where the handle will be fully down and touching them at my desired high pressure. Seems like if the nuts aren’t up against the handle, that could cause it to bang against it when the pressure changes? I will try adjusting it tomorrow and see if it helps.

Still doesn’t explain why the pump isn’t running super smooth, but that’s not as big of a deal. Some of the other pumps don’t run totally smooth either and have been fine for many years. I would prefer to figure out how to make them all smooth though.

 

[OurTown]

Are the pump fed by a gravity tank or city pressure? Is there a difference in the way they sound between HP soap or wax and the rinse functions?

 

[Mchas]

They are gravity fed through a holding tank that sits above the pumps. Not sure about the wax or rinse soap behavior, I will check that today when I go shortly. My guess is probably the same behavior since the only difference is the chemical gets added to the water supply when the solenoid opens.

I will take some pictures too.

 

[Randy]

It almost sounds like your starving the pump for water. Did you plumb the new pump just like the other pumps? Did you use the same unloader? Do you still have the old unloader, try installing the old unloader or swap the unloaders from the good pump next to this pump. What made you think the old pump was on it's last leg?

 

[Mchas]

I am sort of thinking you are right about starving it for water. The two are plumbed the same, except the feed hose for this new one is slightly old and bent/flat a bit. I did try squeezing it to make it perfectly round while the pump was running though and that didn’t seem to make a difference. I used the same unloader just a new one. The reason I thought the older pump was on its last legs is because it was also running rough and I could feel it out in the bay as it got worse. I didn’t bother trying to repair it since it was the only remaining non-Cat 310 that we had and I figured I would just replace it altogether.

Heading to the wash now, I’ll post some updates soon...

 

[Randy]

I am sort of thinking you are right about starving it for water. The two are plumbed the same, except the feed hose for this new one is slightly old and bent/flat a bit. I did try squeezing it to make it perfectly round while the pump was running though and that didn’t seem to make a difference. I used the same unloader just a new one. The reason I thought the older pump was on its last legs is because it was also running rough and I could feel it out in the bay as it got worse. I didn’t bother trying to repair it since it was the only remaining non-Cat 310 that we had and I figured I would just replace it altogether.

Heading to the wash now, I’ll post some updates soon...

Replace the water supply hose!!

 

[Mchas]

Just replaced the supply hose with a new section. Might have helped a bit but hard to tell. I am now wondering if it’s ok and I am making it seem worse than it really is? Here are some videos. The first one shows the much smoother pump next to it, followed by the new rougher pump. The second video shows what happens to the pressure on the new pump when the trigger is released.

Does this seem normal?

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[Waxman]

New water supply hose, like Randy said. Bent / flat hose???? "This ain't yer first rodeo, is it?????"

 

[Randy]

Just replaced the supply hose with a new section. Might have helped a bit but hard to tell. I am now wondering if it’s ok and I am making it seem worse than it really is? Here are some videos. The first one shows the much smoother pump next to it, followed by the new rougher pump. The second video shows what happens to the pressure on the new pump when the trigger is released.

In your video I can't see where your bypass is at, do you have a bypass?

 

[Mchas]

In your video I can't see where your bypass is at, do you have a bypass?

There is a valve to shut off the water supply from the manifold if that’s what you mean? It is wide open now.

I am kind of wondering if the lack of check valve on the out port could be the issue? I noticed all other bays have that except for this one. Maybe when the pump trigger is closed, the pressure flows back toward the unloader for a split second?

 

[MEP001]

You don't need an unloader if you're using weep guns - I'm assuming you are since the pressure isn't dropping to zero when the trigger is released.

The unloader has a check valve built into the outlet, so not having one on the outlet wouldn't change anything.

You may have a bad unloader. I've been switching to unloaders to replace the weep guns with non-weep. I haven't been changing the guns right away when I replumb the pump, and one of them did the same thing with the new unloader.

 

[Mchas]

Correct - weep guns. We have the same unloaders on all other pumps and they work fine. But you could be right, this one might just be bad. I have a few other new ones on hand, I will try another one.

 

[Mchas]

So it turns out the type of weep gun I had was causing the pressure drop whenever the trigger was released. For some reason the Giant brand guns were causing the problem (I tried two brand new ones and both did the same thing). The Kleen Rite brand guns worked much better. Still don’t quite understand why that would be the case, but wanted to post an update in case anyone has a similar problem in the future. Thanks again for all of the help!