Pump Problem - Low Pressure

[Torque454]

I have an AR SXMV4G40 Pump 3450rpm direct drive 4gpm 4000 psi coupled to a 13hp Honda engine. I'm using a size 4 nozzle. I cant get 3,000 psi no matter what I do, let alone 4,000. Even with a new tip. The unloader hasn't been touched, it was set at max psi since, I've been regulating the pressure with tips. I still get 4gpm flow, atleast without a tip in the gun (tested with a 5 gal bucket and a timer) and there is no excessive vibrating in the hoses or anything. It acts totally normal except for 1,000 psi or so missing. I've gotten water in the pump oil a few times but only after water has come in contact with the pump. The oil cap is vented and water can get down inside it. I have run the pump with fresh oil and the water doesn't come back unless i accidentally drive through the rain or spray water at it (not on purpose of course). So i dont think its a seal leak. Also a worn out seal I would think would cause a strong vibration in the hoses and an audible pulse in the spray. The last pump i wore out had those symptoms (i assume from two seals working fine and one not working fine).

Anyways, I have a new tip, plenty of water flow, unloader all the way open, engine RPM is fine, doesnt bog down when the trigger is pulled, etc. I'm stumped?

Also forgot to mention that the pressure on the gauge shoots up to about 4500 psi when the trigger is released which tells me the pump is capable of it, but for some reason its just not doing it.

 

[Mark]

There are numerous possible causes of low pressure.

Wrong size or worn nozzle.
Restricted or insufficient water supply.
Worn packing, o-rings, check valves.
Unloader bypassing..........

Check out the Troubleshooting guide at AR North America

AR North America - Our Goal

Hope that helps, let me know if I can be of assistance.

Merry Christmas!

 

[OKwasher]

take a pair of vise grips and clamp off the unloader return hose while pulling the trigger, if pressure goes up you may have a unloader problem, mine did the same thing, no vibration, ran great, but was low on pressure, i replaced the packings in the pump and one ceramic plunger and did a coil clean and it was back to normal. hope this helps.

 

[Torque454]

My unloader WAS a bolt on type. Keyword was. I have just purchased and installed an external unloader but I havent fired up the machine yet to see how its working now. I did pull the head and the valve caps off and all the seals look fine. If there was a seal out, id think you could see it. But maybe not?

Anyways, i'll try one of my unused tips along with this new unloader and see what happens.

 

[Torque454]

Well I discovered two cracked ceramic plungers in my pump. The odd part is that the pressure comes and goes (as does a pulsation that you can feel) and so does the water being pushed into the oil. Last time i ran the pump it was pulsing and had low pressure and water in the oil again. I may be landing a somewhat large truck washing job and need this pump going asap so i think i may just get a new pump. I cant mention where I get it at i dont think but i can get this pump (4gpm 4000 psi direct drive for gas engine) for $211 with shipping. A heck of a deal. Down the road i will be upgrading pumps and will likely purchase online from a site supporting vendor but for now i have to go the cheapest route possible. a seal kit and two plungers for my existing pump is pretty much the same cost as a whole new pump of the exact same type (And its even an AR pump)