I have a 3 year old Simpson PS424OH (4200 psi) with a Honda engine. It has about 40 hours on it. I was doing a job today, and everything was running fine. Plenty of pressure, no issues with the engine, hoses or attachments.
After stopping to move the unit to the sext section, after restarting the engine, engine was fine. Still really good water pressure from the spigot to the pump, but it just isn’t generating any pressure. I’m just getting meager pressure at the wand tip or through the surface cleaner; about similar to what I’d expect with just the regular garden hose pressure. I have a ball joint at the end of my pressure hose, and if remove my sprayer and I close the hose off a bit, I can hear the engine bog down slightly like it normally does once it starts pressurizing the pump, but I’m just not getting anything near the type of pressure I’d expect. With all the hoses open and running, I’m not hearing the engine bog down like it is pressurizing.
I’ve tried swapping the pressure hoses, with no change. I’ve checked all the o-rings and have no leaks. I’ve checked the water supply screen/filter and it isn’t blocked. I’ve tried swapping between a wand and surface cleaner with no change. I’ve tried turning the unloader on the pump through the full range of motion with no change. My thermal bypass looks fine and I tried letting the thing cool down to see if that would help, but no change.
I’d really appreciate any ideas. I’ve never had a dead pump, but this is what I imagine it would be like.
I’m not familiar with this setup, but I’ll give it a shot and hopefully there’s cross reference to equipment I’ve worked on.
With the hoses open you wouldn’t necessarily hear the engine bog down because you are not putting the pump under load. If you have a gun attached but closed, the back pressure to the unloader keeps it closed and in bypass mode. When in use, the release in pressure opens the unloader and puts the pump under load. This will cause your motor to bog down but the governor linkage on the motor to carb gives it more gas, so the engine doesn’t die. You should see the linkage move as you open and close your gun. Open the top oil fill cap on the pump and with the motor running make sure you see the plunger guides moving. Also, most bell housings that attach the pump to motor will have a slit where you can see the engine/pump cranks spinning. If you don’t you probably have a sheard crankshaft key. I suspect these things will be fine, but worth a look. I suspect something on the water side of your pump is the issue.
On the opposite side of the unloader, above the relief valve, there should be a plug. Remove the plug and start the engine. You should get a lot of pressure coming out, so don’t stick you face down there. If there is any sort of air pocket in the head, this will clear it out and if you have good pressure, tells me that the packing inside the pump head is good. Once the plug is back in try it out and see if things are back to normal. Inside the pump head are check valves behind those six brass plugs-3 on top, 3 in front. Since you don’t have a chatter in your gun, I suspect the check valves are fine.
If still no pressure, take a look at the unloader. When you pull your gun trigger, the black knob should pop up and pop down when you release the gun. If it doesn’t, it’s an issue. On top of the black knob, the top should pop off to expose the stem and attached nut. Remove the nut and spin off the knob. You should see the spring with a washer on top. If the spring is broken, obviously this is the problem, but happens rarely. On the stem there should be two small brass nuts locked together toward the bottom 3rd of the stem. These nuts are the stopping point of how far down you can turn the knob and increase your pressure. If one of those nuts has worked its way up the stem from vibration, it will limit how much pressure you can adjust the knob to get. If so, spin it back down the stem and tighten the two nuts together. Usually there’s a dab of a clear locktite where the factory set the brass nut at. Hopefully something here solves the problem. Good luck.
