CAT 31DS Pump issues

[DJWashCo]

I've got a mix of CAT 310, 310S and 1 31DS pumps in my wash, and I'm having a bit of a struggle with the 31DS. Before I throw in the towel and order a new 310 to replace it, I want to see if anyone has any thoughts.

This particular pump pulsates and in general doesn't seem to be developing as much pressure as my other 310s. I have rebuilt it (new seals and valves, new seal cases, verified that it is not washed out - it looks like new inside), and the only thing that I could find different between this and a 310 is that there don't seem to be plunger O rings as the plungers just come out when you unscrew them (it seems that the rod threads all of the way through). I've also replaced the regulator and verified that it is running at the proper RPM, but it still is pulsating. I've also verified that it is not getting air anywhere upstream.

Does it sound like I have missed anything, or does anyone know of anything with a 31DS to look out for? I can't find much info on them, even on CAT's website.

 

[Blanco]

Give it a different inlet water source and see what you get. Maybe try swapping inlet from another pump. If there is a check valve on the current inlet then it may not be opening all the way and starving the pump for water.

 

[DJWashCo]

Give it a different inlet water source and see what you get. If there is a check valve on the current inlet then it may not be opening all the way and starting the pump for water.

Crap, should have noted above - I checked that as well (changed the inlet hose to make sure it had not collapsed internally and checked the valve to it to make sure it is fully open - it is on a manifold with 4 other pumps feeding from the same source). No check valves on the water inlet with my setup, however there is a check valve on the soap feed to the secondary which I will replace and see.

 

[Waxman]

You can also check the outlet side by hooking up a hose and gun assembly inside the equipment room. That way you'll verify there's nothing going wrong downstream as well.

 

[I.B. Washincars]

The 31DS is a 310 that was OE for a Mark VII pump stand. I think the only difference is that the head is not chromed.

 

[Blanco]

The 31DS is a 310 that was OE for a Mark VII pump stand. I think the only difference is that the head is not chromed.

I was wondering why I never heard of a 31DS

 

[Randy]

Try this, disconnect the soap and wax lines from the pump and plug the ports and then run the pump, if the pulsating go away then you know the problem is in the soap and wax delivery side. Another thing you can try is to connect a city water hose to the pump water inlet and see if the pulsating goes away.
It was my understanding that the Cat 31DS was the model before the 310 with a un-plated head. I think I've got one in my attic.

 

[Blanco]

Try this, disconnect the soap and wax lines from the pump and plug the ports and then run the pump, if the pulsating go away then you know the problem is in the soap and wax delivery side. Another thing you can try is to connect a city water hose to the pump water inlet and see if the pulsating goes away.
It was my understanding that the Cat 31DS was the model before the 310 with a un-plated head. I think I've got one in my attic.

Do you know around what year the 310 became manufactured. Curious.

 

[Randy]

Do you know around what year the 310 became manufactured. Curious.

The serial number is the date code when the Cat pumps are built. I'll see if I can find the pump I have that is a 31DS. The pumps at my car wash have a chrome head, they were made in 1982. So the 31DS with a brass head had to have been made before that.

 

[Blanco]

The serial number is the date code when the Cat pumps are built. I'll see if I can find the pump I have that is a 31DS. The pumps at my car wash have a chrome head, they were made in 1982. So the 31DS with a brass head had to have been made before that.

Wow ya I wasn’t even thought of then

 

[I.B. Washincars]

My Mark VII pump stand from 1990 came with the 31DS pumps. I think it was just something they did for Mark VII.

 

[DJWashCo]

That you all, I am going to offline that bay tonight and do a bit more troubleshooting. I've had a line of cars most of the day today so it hasn't been a good day to do anything with it.

My wash was built in 1996, so if this is that old, it makes me wonder if it was a secondhand acquisition.

Appreciate all the ideas, info and help!

 

[Greg Pack]

My Mark VII pump stand from 1990 came with the 31DS pumps. I think it was just something they did for Mark VII.

Why I never liked Mark VII. Just different enough to say it's a "special" proprietary pump without really being any different.

 

[TMoliver]

It has been many years since I tore down a 31DS . The difference if I remember correctly was the plungers were shorter and the crank slightly different ,everything else was the same .