Help Needed to Diagnose a Problem

As most of you know, I’m not in the pressure washing industry.

But I do have a decent piece of equipment. Northstar machine, 4000PSI/4GPM. 13HP Honda engine and Cat Pump 4SF40GS1.

I’m not getting pressure.

Engine running fine. Pulled it out of the garage and fired right up.

Had pressure for a few seconds, then nothing.

No water in visible in the oil level window on the pump. That happened a few years ago and water was spurting out of the hole in the pump oil cap, so I replaced all pump seals and that solved the problem. No leaks aside from a slight engine oil leak that’s been eluding me since Bush was in office.

I noticed last year when I was using the machine that from time to time, I’d lose pressure. Engine didn’t struggle or choke, pressure would just drop mid-stream. I’d release and then give a few quick blasts on the trigger, and I’d see pressure again. Now - not. I had pressure immediately upon starting, then lost it, never to regain it.

I don’t know enough about these things to diagnose, and would appreciate any opinions before I start throwing parts at it.

Note: the knob that (I think) adjusts the pressure on top of the unloader is frozen solid. I’m not a small guy and I can’t turn it a bit. Then again, I haven’t attempted to turn it since 2001.

Secondary problem: Both wheels are shot to hell. I’m sick of buying fix a flat so instead I bought new wheels, but how do you get the old ones off? There’s no bolts, no cotter pins, nothing. There are what looks to be some sort of perforated washer on the hub - do I cut that and just hammer the things off?

Thanks in advance for any help you can provide. Whoever can lead me in the right direction, I’ll print anything you need marketing-related at cost. Least I can do.

Hope everyone has a great weekend.


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I would start with the unloader. See if you can pull it apart and clean it up. Maybe it’s just seized.

As far as the wheel I would guess they’re being held on by a push ring. You can sometimes get them off, bend the tabs back, and reuse them but they often get damaged in the process. You can buy replacements at most hardware stores. They have different sizes.



You can also replace the push rings with shaft collars. See some here:


That’s EXACTLY the beast that’s holding the wheels on.

I was leaning toward unloader - thank you for confirming. I’ll pull it off this evening and see if I can shine it up. If not, not a huge deal. Replacements aren’t unreasonable.

You da man, Brian. Much appreciated.


Wouldn’t hurt to have a quick read here, scroll down a bit…

Defective shutter valve, causing pump to go into partial bypass, maybe.

2001, might be time to replace it.