Pressure spike

[Andrew Bandarovich 39]

I have Delco Cobalt 5gpm 3500.

I put a gauge on the gun to see if the nozzles worn out. When i squeeze the trigger gauge shows 3200 psi, when i release pressure jumps to 4000psi and then goes to 4500 psi within 10 seconds. Why is that? I dont like having 4500 psi inside 4000 psi hose. And if you put DS nozzle on and squeeze the trigger the recoil almost dislocates your shoulder!

Edited October 3, 2009 by Andrew Bandarovich

[PressurePros 248]

Adjust your unloader to keep your pressure below the pumps rated psi. It will not affect flow if you do it correctly. Its a good way to prevent that spike as well. I adjust my unloaders to bypass at 1500 psi or so. The key to not affecting flow is using the right nozzles.

Edited October 3, 2009 by PressurePros

[Beth n Rod 1,279]

Sounds to me like the unloader isn't working correctly.

From what I understand, the unloader senses when the pressure goes up and shuts off the flow to the line but the amount is set in accordance with the working pressure.

Your spikes are a bit high which tells me it has something wrong with it...hopefully, one of our astute mechanically inclined members can shed some light on it for you.

Rod!~

[Russ Johnson 141]

The unloader should kick out at 10% above operating pressure, so you should unload at about 3850 psi...4000 isn't too far off. The pressure climb could be: hot water expansion in the line, or a slight damage to the o ring on the outlet piston in the unloader, allowing water to seep past it into the hose.

[plainpainter 217]

I screwed around with my arrowline 3650psi unloader - and there is a lower nut that is hidden that you can adjust downward - and I dabbled with it and on my gauge saw pressure spike to as much as 5000psi. Then I adjusted the nut back up - and then reassembled the spring over it. You can get higher pressures, it's just these suckers are set from the factory to max out at 3650, and all you can do is adjust the upper nut to lower the pressure from that. But if you start dissambling it - you can find that lower nut that will give you even higher pressures - I would dissamble, remove the spring and turn that nut back out and reassemble.

[Andrew Bandarovich 39]

The unloader should kick out at 10% above operating pressure, so you should unload at about 3850 psi...4000 isn't too far off. The pressure climb could be: hot water expansion in the line, or a slight damage to the o ring on the outlet piston in the unloader, allowing water to seep past it into the hose.

Russ takes the prize! I checked with cold water and the pressure isnt climbing up. 3200psi on/4000 off.

Thanks guys and gals.