8 gpm presssure surging, losing pressure

My 8 gpm, 3k psi with a K7 is surging. It only happens after the machine has been running for an hour. The machine surges with a weird noise and looses pressure. It also does it in bypass when I’m off the trigger. When that happens no water bypasses for a second. Same sound from the machine. First video you can’t see loss of pressure but you can hear it. 2nd video you can see a little better the loss of flow/pressure.

Its seems like it’s not getting water the way it loses pressure/flow but the buffer is full and the filter isn’t clogged.

Do you have any supply line leaks anywhere? Although, it would start surging right away and not wait an hour. I wonder if a coil on the engine is starting to go bad and doesn’t start acting up until it gets hot.


The engine sounds normal till it does that surge. It is a Predator motor so who knows. It’s leaking oil where the gear drive box meets the engine but I wouldn’t think that would cause a loss in pressure.

I would double check water supply line for leaks. Might as well check for leaks on the pressure hose side too even though a leak at that side shouldn’t cause surging as long as you’re on the trigger.

I think it being the coil is a stretch but easy to check. Normally when they go bad they will constantly have weak spark or just no spark at all. Sometimes they will work until the engine warms up and they get hot. What makes me think it’s the engine is it doesn’t start surging until about an hour into it. You would think if it’s a leak or in the pump it would start right away.

Maybe try and run it without your chemical injector. I had a spring break once and a small piece got sucked into the quick connect and caused issues. I mainly had really low pressure but it did surge a little.

The spark plug tester will have a bright orange flickering light the whole time. When it’s surging see if the spark falls off a little bit. Any auto part store will have them too.

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My pressure hose is leaking at the reel. The drum was full of water the other day. I had to pull the hose for repair and the drum the hose wraps around was full of water. My reels are 3 years old and never replaced the swivels. Steel Eagle reels and I run chems through them.
My employee has also been switching chem injectors back and forth between my 5.5 and 8 not realizing they are different sizes trying to stop the surging. I’ve seen it on both injectors. I did run my 5.5 on the same reel and felt a slight loss but it was so slight it could be me just imagining it.
Maybe @Hotshot @Innocentbystander have seen this before.

How do I know if my swivel is bad?

I forgot to mention that my K7 bypass orifice is the wrong size. It’s a 3 and I need a 2. Waiting on it from South Side. I might swap the 3/8 bypass for a 1/4" and see if it stops. Problem with that is it blows the 1/4" bypass lines out constantly.

Your swivel is bad if it is leaking. Is your hose leaking or the drum manifold on the reel?

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I didn’t see it leaking but there was water inside the drum. Under the quick connect.

Unwind the hose, for up the machine and see where it’s leaking. Don’t run your fingers around looking for the leaking, they’ll get cut off you have a small leak on the manifold

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Feel around inside the reel drum?

I don’t know what your drum looks like. I just don’t want you sticking fingers around feeling for a leak. Should be simple to tell if its the drum or hose leaking.

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Is your manifold leaking, Im not following , if the swivel is leaking either get a repair kit or a new swivel from pressuretek / Barens.

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It’s not the manifold. I think the gearbox is going South. It’s been leaking oil and I’m waiting on a O-ring for the gearbox. I just changed oil and found metal in drain cap. Maybe gears are slipping and that is the loss of pressure. Would the that explain why the problem is starting after an hour of run time?

Absolutely. Forget the Oring , Its new gearbox time bubby, Better get one before she locks up on ya. how old is the gearbox ? Golly thats alot of metal !
Sorry for your troubles Bill.

If your gearbox is like mine, Im wondering if the gear on the pumpshaft is moving. Its the gear with the set screw.

Ok. I was hoping you wouldn’t say that. I just got it in March of this year. The pump was installed on it I just put it on the machine. I have no idea what I did wrong. I know the oil got pretty low the other day. No idea how long my employee was running it for with low oil.

That ill do it for sure. Like Grunt said I’d call were ever you got it from. That thing should last years not months sir.

I checked the oil every day. One day it was really low. He could have been running it for hours with low oil. Would that do it? It’s been leaking oil for months though. Worse now. I got it from Envirospec. Pump and gear drive combo. Pump already attached.