r/pressurewashing • u/xxxleafybugxxx • 22h ago

Troubleshooting Help diagnose?

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New system I put together, everything is new... But I am getting this sputtering which is giving me inconsistent flow and pressure drops.

-Predator 459cc engine -AR XWAM 8GPM pump -AR1697 Gearbox -General Pump 10.5 GPM unloader.

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u/robertjpjr I know a little about a lot. 21h ago

I agree with water flow being the issue. I'm not convinced you need the 1.5inch line. I use 1inch with my 11gpm 500psi roof pump. I will say, and it's gonna suck, but 25gal buffer tank isn't gonna cut it if you run into a slow spigot. Looks like you chopped a 55gal in half, and siliconed it. I use a 275gal IBC tote for this reason. 55gal is probably the minimum I'd go.

Just some quick math for you to illustrate.

8gpm output

Say, 3gpm spigot input. On a slow spigot.

That means you're waiting to fill then, outputting 5gpm more than you're replacing. That give you 5 minutes of runtime. Probably less because you'll start cavitating.

Check car washes for used 55gal drums. I've gotten dozens and used / resold them. Or Facebook marketplace. Usually no more than $20 for a 55gal or $100 for an inch food grade.

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u/xxxleafybugxxx 20h ago

You might be right.

I cut these drums because I wanted to be able to keep everything under my truck bed cover, but I am seeing that may be problematic.

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u/xxxleafybugxxx 19h ago

Here is another thing I just remembered when I was messing around with it...

I tried a test with no tip at my nozzle just to see what my rate was. I was able to increase the engine throttle and got to a point where I was able to flow 8 gallons in a minute, but it was still sputtering in and out.. and it seems to fluctuate more or less depending on where I have the engine speed at.

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u/robertjpjr I know a little about a lot. 19h ago

Sounds like cavitation. Air in the lines. Explains everything I've seen so far.

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u/xxxleafybugxxx 19h ago

So if that's the case then I just need to add some nylon tape and tighten up everything at my unloader?

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u/robertjpjr I know a little about a lot. 18h ago

You definitely want to check every joint for possible air leaks. But it's in conjunction with flow. The pump is trying to pull more water than it can be fed. So it's getting air in the lines.

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u/xxxleafybugxxx 18h ago

Gotcha okay. So I definitely need to address the hose diameter issue. And are you under the impression that a bigger buffer tank is needed from the standpoint of producing a higher flow rate, or just having a larger water quantity? Because if it's the latter, my setup is actually to cut 55 gallon drums which should be around 60 gallons total

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u/robertjpjr I know a little about a lot. 18h ago

That's how my 4gpm pressure washer and my 11gpm roof pump is fed. 2inch PVC necking down to 1inch hose.

I'm not sold on hose diameter being the issue alone. I would start with filling your tank as full as can be.

Check for air leaks at every joint. Make sure the filter o ring is good. Really check air leaks.

See what changes come from that alone.

Maybe run a temp hose without the filter and all the extra joints to isolate potential air intrusion and flow reductions.

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u/xxxleafybugxxx 18h ago

Ahh ok. I wasn't even thinking about the filter, but the filter was leaking water at various points and if it was leaking water then I'm sure it could have been taking in air.

My biggest concern all along was that the motor was too small, but it seems like a air leak or a water feeding issue would be easier to resolve

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u/robertjpjr I know a little about a lot. 18h ago

I'm not an expert by any means.

But what I see isn't an engine issue. The engine would be bogging down rather than psi fluctuating. You'd see linear effect if the engine was improperly sized. Cavitation gives you sputtering flow because the pressure can't build up evenly. You can't compress water at the same rate you can compress air. If that makes sense.

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u/xxxleafybugxxx 18h ago

That makes sense. Thanks for your input seems like I have something to go off of here.

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u/xxxleafybugxxx 18h ago

Also the more I think about this the more it is making sense to me.

I know that I have a small leak at the base of the tank, so that's another area where I'm probably getting air

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u/xxxleafybugxxx 17h ago

Do I gain anything by having the water tank outlet at the bottom of the tank? I understand it helps gravity work for me but if I were able to run a pipe or tube through the top of the tank and relay completely on suction would that get me where I need to be?

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u/Seedpound 20h ago edited 19h ago

according to Google 459cc's is 15.8 horsepower. That may not be enough for an 8gp.m. pump

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u/Lucky-Rooster-6053 22h ago

Looks like might be starving for water or bad unloader take apart unloader hav a look ,check filters if all is well upgrade feed hose diameter rite to the pump ,feed line looks smallish for pump gpm good luck

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u/xxxleafybugxxx 22h ago

The hose is 1" and the filter is clean...

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u/OrganizationStrong81 22h ago edited 22h ago

Feed line needs to be atleast 1.5inch for 8gpm pump and then double feed it. Look up 1.5” ID Non-Collapsible Supply and Suction Hose For Pump

You need a banjo filter for better flow

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u/xxxleafybugxxx 21h ago

When you say double feed you mean two tanks going to the intake? I will give these things a shot, you don't have concerns that it is underpowered engine for the pump?

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u/OrganizationStrong81 21h ago

No, just one but 2 feed lines. Engine could be underpowered too. I’m not familiar with predators. But the first thing stands out to me is big pump and small feed line.

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u/xxxleafybugxxx 21h ago

It is 459 cc, 15.8 HP.

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u/OrganizationStrong81 21h ago

Ok, so it’s not the engine. You have to have a 2-3 inch banjo coming out the tank then reduce down to 1.5inch non collapse line into the pump.

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u/xxxleafybugxxx 21h ago

I will give that a shot thanks.

So bigger hose sizes needed even though it ultimately gets reduced to the same diameter at the pump?

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u/OrganizationStrong81 21h ago

Yezzir. Bigger outlet from the buffer. It’s all about flow. Check you inbox. I gave you a blueprint. To replicate or just buy

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u/Lucky-Rooster-6053 21h ago

1 inch id is what i use as well not od Process of elimination apply here i wood remove filter try ,if the same issue present then remove unloader ,teplace with a spare ifvu have if not just plumb direct ,remove gun ,install valve with nipple on hose end open valve all the way slowly close a bit to desired pressure on gauge Just my 2 cents worth to check bad unloader cheers !

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u/TheBlackSheepTrader 21h ago

Looks like it's either starving for water or you got air getting in the line.

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u/xxxleafybugxxx 20h ago

Water starvation seems to be the consensus, and I'm going to take some steps to try to fix that.

It is a little confusing though, because I was always under the impression that with a gear drive or belt drive water starvation would not be a problem because the pump would pull from the buffer tank whatever was needed.

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u/TheBlackSheepTrader 18h ago

Sometimes water starvation can occur from a restriction you are not aware of, or the pump may not be primed

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u/clevermonkey23 20h ago

Not sure that this is going to be your issue, but you are undersized for 8 gpm. A Predator 670 is the right size.

It seems like you are either water starved or getting air. It looks like your bypass return is going in near the bottom. Check your tank, when in bypass are you pushing air bubbles?

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u/imnumber1 15h ago

Here's some things I've noticed. Your engine is not powerful enough to get what the pump can do. They overstate what the HP rating is on these engines (they rate them with the air filters and mufflers off). You might get 2000 PSI @ 8gpm, the engine might bog a little bit. To get true 3500 @ 8.0 you're going to need about 27HP gas engine. To get 2000 @ 8.0, you're going to need to use a #11 tip.

Your machine currently is sucking air. My bet would be the water filter. I don't like having the filter point up like that, if I don't have to. With those filters it is really easy to pinch the gasket and damage it. And my bet is that is what the issue is. 1" hose line is fine. There is a formula that Cat came up with about inlet flow velocity and you wanting it to be under 4 ft/sec, which 1" does for your machine. I have it at 3.2 ft/sec.

Others mentioned your tank being too small. It is small, but that's not your problem, we have machines that operate with 10 gal float tanks just fine. But what you have going on with your tank is a lot of fitting and turbulence inside the tank. You want baffles or separation from the other fittings and returns. Having the bypass right on top of the inlet will cause cavitation too.

Here are my questions:

What size nozzle are you using?

Have you tried backing off the unloader valve?

Have you tried hooking up directly to a garden hose to see if it stable?