Working pressure low, idle pressure very high

4gpm 3500psi Cat pump on honda engine.
new seal kit on pump, new unloader, black spring

red tip 40 size, working pressure is very low, release handle pump reads ~2000psi higher than working pressure, not a fast spike, but a quick build up, unloader cranked down maybe 3/4

what am I doing wrong?

You need to adjust your unloader. Adjust til the is only a few drops, or small trickle in bypass when trigger is squeezed. Gauge is not necessary.


Specific newbie questions with supporting video make me happier than I can likely convey.


And the question gets answered quickly


Dont let crypes see this. It may ruin his opinion of the forum. :smile:

1 Like

Who cares? Lol

So the gauge reading 4000-4500 on my 3500 machine is ok?

Scared me.

Gauges are not always accurate and when you adjust your unloader I doubt you’ll have that high a pressure reading. Lot depends on how much hose you are running. Adjust unloader with all your hose on the reel.

1 Like

Only 50ft of hose.

I’ll try and report findings.

This is exactly what mine was doing and I didn’t realize I was running 1,000 rpm too high. @Innocentbystander figured that one out over the phone though. The man has forgotten more about pressure washers than most of us will ever know.

It’s been almost a year, and I have another question regarding getting this unloader set correctly.

I’d like to set it according to the "turn the pressure up unitl you’re bypassing just a small amount of water’.
My question is, how do I do that “safely”?

My cat pump has a 3/4inch? hose that bypasses from near the unloader and runs over to where the garden hose would hook up. If I unhook that, won’t water just spray everywhere? Won’t the pump starve for water? Will anything high pressure be coming out anywhere that could be dangerous?

I haven’t seen any videos or anything of anyone doing it that way.
Could someone give me some pointers, I don’t want to blow up my pump or do anything unsafe.

Also, side question, I can start a new thread if it’d be helpful:
I have a 4gpm pump and size 4 tips, if I run my red tip I should be able to produce my rated 3500psi with a 4 tip on a 4gpm pump? I only get around 2000, I have just rebuilt the pump with all new seals, a 130$ investment. Do I need to drop to a smaller tip to get my pressure albeit probably losing gpm? Or maybe my unloader is set to low? Pressure gauge right after the unloader shows 2000 working psi with red tip, and climbs to 3500 when not spraying.

Thanks ahead of time!

Can you post a picture of your unloader? It should have another plug for bypass that you can pull off and put a 1/4 barb and hose for setting it. I guess you don’t really need a barb to set the unloader. It would just give you a way to direct the water flow from bypass while setting the unloader.

What size orifice does your red tip have?

I’ll grab that info when I get home, thanks!

1 Like

Sorry that took so long to get pictures, here they are.
And the red tip is a zero degree 00040

1 Like

@marinegrunt bump…

I think I would just pull the hose off of the barb closest to the garden hose connection, plug it, and watch the flow out of the hose coming off the unloader. Actually, I would pull the hose off of the unloader, pinch it off with some vise grips, and just let the bypass water shoot straight out of the side of the unloader. Either will work. Once it’s set just put the hose back on. Another option might be pulling the plug on the left hand side of the unloader. That could also be a bypass but not sure.

Once you you’re ready to set the unloader just pull the trigger and turn the unloader until water barely trickles out of the bypass.

Do I need to worry about hurting anything doing it that way?
Does it matter if the trigger is pulled or not with the bypass unplugged? I don’t want to starve the machine of water or anything.

Can that hose be off the whole time I am setting the unloader? Like trigger pressed or not? Can I start up the machine with that hose off without damage?

Also, any reason my pressure is so low with a 0040 tip?

Should I be setting the unloader with a tip that actually gives me the pressure I am going to want to work with?

When you pull that hose off to set unloader you don’t want to let off the trigger. As long as your on the gun water is flowing and still cooling the pump.

According to a nozzle chart that red tip puts out the correct gpm to where you should get your 3500 psi. Granted, you might not reach 3500 psi so just set your unloader until the bypass barely trickles. Don’t even worry about the gauge for now. If you want to throw it back on after your done setting unloader to see where you’re at you can. Once you’re done setting the unloader put that hose back on.

If you wash a lot I would consider a buffer tank or one of those weeping guns or whatever they’re called.

Ok, I’ve collected some videos on what I’ve tried, as the outcome doesn’t seem right.

First video is after setting the unloader by watching the bypass output, I put a gauge on afterwards to show pressure after adjustment. The video is of minimal bypass with the gun engaged with the red 0040 tip.

This video is bypass hose hooked up, on and off the gun after adjustment. My spike pressure (max) doesn’t reach the 3500 that my pump is rated for, if I set the unloader to trickle. I can get it up to 3500, but there would be nothing coming out of bypass.

This is on and off the gun with the 2nd story soap tip. Something doesn’t seem right. Could it be the unloader? I have replaced it because my last one was surging on and off, the old one was a black spring so that’s what I replaced it with. Am I doing something wrong? I had way more power before.


Did you have more pressure or more volume before changing unloader? It looked like you had a lot of reach for 4gpm.