Cannot build pressure...


New Member
I have an AR model# XMV 3G30 water pump that I am having trouble fixing.

It is not building any pressure at all. The motor never bogs down when I pull the trigger, but the pump shaft is rotating along with the motor.

I replaced the unloader, cleaned all of the check valves and still nothing. Just the garden hose water pressure flowing through...

Can anyone give me any ideas what to inspect next?



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Pump Runs but Produces no Flow Pump is not primed.
Flood suction then restart pump.
Pump Fails to Prime Air is trapped inside pump. Disconnect discharge hose from pump. Flood suction hose, restart pump and run pump until all air has been evacuated.
Pump Loses Prime, Chattering Noise, Pressure Thread Fluctuates
1. Air leak in suction hose or inlet fittings. 1. Remove suction line and inspect it for a loose liner or debris lodged in hose. Avoid all unnecessary bends. Do not kink hose.
2. Clogged suction strainer. 2. Clean strainer.
Low Pressure at Nozzle 1. Unloader valve is bypassing. 1. Make sure unloader is adjusted properly and bypass seat is not leaking.
2. Incorrect or worn nozzle. 2. Make sure nozzle is matched to the flow and pressure of the pump. If the nozzle is worn, replace.
3. Restricted intake. 3. Refer to above priming information.
Pump is Noisy Pump sucking air. Check suction manifold.
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New Member
While I agree with all the standard troubleshooting guidelines, air leaks in the suction side of a PD pump are normally not a large contributor to a "no pressure" problem as are other factors when a garden hose is directly connected to the inlet due to the fact that water is being forced into the suction side and leaks will normally manifest themselves as water leaks rather than air being drawn in. You have 50-70 PSI of water at the suction side when you force feed it and atmospheric pressure is only around 14 PSI. You might have to crack a fitting at the discharge to allow air trapped in the pump to escape.

Whenever I'm unsure of a "no pressure" cause and it's not 100% as to why then I will remove all accessories from the pump suction side, (unloader valve, aux. suction fittings, etc.) plug the openings and try that way. This is not always practical with one piece heads w/unloaders built in. Just remember to NOT release the trigger gun when trying this because there will be no unloader valve to relieve the pressure if it should build pressure.

In your case the most possible cause other than an unloader problem might be from worn seals or stuck or leaking valves. If the pump refuses to pump water with a good unloader installed or no unloader then I would consider re-inspecting the valves and o-rings as well as the piston seals. Other than that would possibly be a defect or failure in the head casing.

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