cat pump problem

[washman9]

have 5cp 2120 cat pump, having problem with high pressure pulsation. pump generates good pressure, regulator adjust up and down fine, replaced all valves, not evidence of leaking head or bad seals, no evidence of it sucking air from inlet line, etc. any thoughts?

 

[I.B. Washincars]

When you replaced the valves were any of the o-rings broken? If so, you most likely have a matching groove in the head. Also, when you have/had the seals out, did you check to see if the head was washed out? Washout in either the valve or seal area will cause pulsation and nothing short of a new head or machining for inserts will fix it. Both options are expensive.

 

[washman9]

none of the o rings appeared broken. i have not replaced the seals just assumed they were ok since the pump is not leaking. i am not sure how to visually identify wash out in regards to the head.

 

[MEP001]

Worn low-pressure seals will cause a leak but won't usually cause a pulsation. Worn high-pressure seals can cause a pulsation but won't create a leak.

If the pulsation is constant whether the trigger is pulled or not, it's likely a pump problem. Pull the valves out again and make sure the o-rings are still ok. If one is cut or missing, look into the area where the o-ring contacts for a groove. Be sure the valve itself is ok - there could be a cracked poppet (Disc that moves and makes the seal) or debris stuck under it keeping it open. If they all look ok, pull the head and check the seals.

A plumbing leak allowing air to the pump will usually cause the pulsation to change or go away when the trigger is pulled and released.

 

[washman9]

i re examined the problem today. when the trigger is not pulled the pump holds 1100-1200 psi very easily and the regulator will move the pressures up and down, however when the trigger is pulled pressure drops to 600 and the regulator will not move pressure up or down.

 

[Randy]

Try switching the regulator from one of the other pumps and see if the problem follows the regulator. If that doesn?t work try putting in a seal kit on the pump.

 

[MEP001]

If it's still pulsating, the regulator is not a likely culprit. Did you address my suggestions and see if the pulsation remains constant or changes with pulling/releasing the trigger? More than likely you have a bad seal, valve or o-ring, or you have a leak allowing air to the pump. Another possibility would be a thrown rod, but there's not enough room inside the 5CP housing for a connecting rod to come apart and not have parts hitting other parts until it breaks a hole in the crankcase.

 

[washman9]

appreciate suggestions, will try switching regulators and then pulling head if necessary. pulsation is constant with pulling / releasing trigger.

 

[Randy]

If you have to pull the head apart, be sure to look for any signs of head wash out. The 5CP pump is known for head wash out.

 

[washman9]

ok, so far, new valves, new seals, and regulator. there is improvement but pump still looses pressure when trigger pulled about 100-150psi. is there anywhere i would be able to look at pictures of head wash out so that i will know what i am looking at. thanks,

 

[MEP001]

Did you change the tip? Did you confirm that there's no loss of flow through a check valve at the boom or the weep? Is the pump still pulsating?

 

[washman9]

yes, we have tried interchanging with several different wand / tip assemblies.

 

[phred113]

With the trigger open, adjust the pressure downward until the pressure starts to drop in relation to adjustment. Then, close the trigger a few times. Read bypass and spray pressure. You may find that the difference is 100-150 psi. This difference will tell you the efficiency of your regulator. Some regulators will have a 100 psi pressure variance. Your pump could be fine and your regulator could be causing the jump. A very good regulator will have a pressure differential of 25 psi - cheap ones can be 100+ psi.

 

[taz6122]

I'm sure this has been taken care of by now but for future reference, in my case it was debris caught in the valve spring. Used the air compressor to blow it out and wallah!

EDIT: Sorry I missed that you had replaced valves.