Cat Pump cup replacement keeps failing???

[Rudy]

I have recently replaced the cups on a Cat Pumps 623.

Then the pump would run fine for 2-3 days.....smooth and good pressure.

After several days, the pump loses pressure....and then runs very rough.

Every time, a cup has become dislodged from the cup holder.

What could be going on? This has happened multiple times.

 

[Rudy]

BTW....when this pump first starts up, it takes about 5 seconds for the pressure to build up. This makes me wonder if there's an inlet issue which makes the cup "run dry"....and that's what is causing it to unseat.

 

[I.B. Washincars]

Is the head washed out?

 

[Rudy]

The 623 has valves in the head.

Doesn't the head washout problem exist in plunger style pumps (which the 623 isn't)?

 

[MEP001]

What pressure are you running? 623 pumps are only rated to 1200 PSI.

Are you replacing the cup on the the machined piston? Maybe you're not getting them seated properly. There's a tool that makes it much easier.

 

[I.B. Washincars]

The 623 has valves in the head.

Doesn't the head washout problem exist in plunger style pumps (which the 623 isn't)?

I admit I'm not familiar with the 623. Every pump I've dealt with was prone to washout, so I assumed a 623 could be as well.

 

[Rudy]

I just off of the phone with Cat Pumps Tech support.

It turns out that there are 2 DIFFERENT piston types....Machined Pistons, or Bac-Cup Pistons. I was trying to use Bac-Cup "Cups" on Machined Pistons.

To use Bac-cup cups on a machine, the machined pistons need to be replaced with Bac-cup pistons (Bac-cup cups are much cheaper). The Bac-cup setup ALSO needs a teflon backup ring. Machined Pistons do NOT use this teflon backup ring.

Parts arriving tomorrow. I'll let you know how it goes.

 

[MEP001]

I hope you ordered the cup tool as well. They're just about impossible to install without it.

 

[Rudy]

If you mean the thimble-sized plastic inserter...yes....Thanks.

 

[washnvac]

I stopped ordering just the rubber and oring because it is such a p.i.a. to get on and seated properly, even with that so called tool. I just order the whole assembly kit for $18.20. Then I know it is right. They do not need replacing that often, anyhow.