I’m experiencing an issue with my pressure washing setup and would appreciate any troubleshooting advice.
Setup:
Honda GX690
General Pump 8 GPM belt drive
K7.3 unloader
Less than 30 hours on the unit
Problem:
When I trigger the wand under full engine throttle, I get full pressure for the first second or two. After that, the output drops noticeably, and flow becomes much weaker. The unit is still bypassing properly, and I don’t notice any leaks.
Steps I’ve Taken So Far:
Bypassed hose reels and injector — ran directly from unloader with a good hose — same issue persists.
Checked water supply: tank is vented, float valve working, filters are clean, and flow appears sufficient.
Fuel levels are fine. I replaced the fuel filter, which showed a slight kink from the clamp.
No noticeable engine lugging or surging during operation.
Unloader appears to function correctly — it bypasses without any erratic kick or hesitation.
No leaks or clogged nozzles found.
At this point, I’m unsure if the issue lies with the engine, the pump, or the unloader. I’m leaning slightly toward a possible fuel delivery problem, but I would expect the engine to struggle across all loads if that were the case?
Any insights, especially from anyone who’s seen something similar, would be greatly appreciated. Thanks in advance!
Initially when it was set I was getting a light trickle, i wasn’t able to tell how much on the gun when I was troubleshooting initially but I will check next chance I get.. I am also noticing at full throttle I am only getting about 1500 psi at the unloader.. I believe I had it set to around 3700 initially so something is causing the drop. I think I had some bad fuel leftover in a can I used to refuel and it’s causing the problem but I don’t know for sure. I plan to replace the fuel pump and carburetor tomorrow and then I will clean out the old ones as replacements as well. I have another unloader coming as a spare but it is the same as what I have currently installed. Is there something specific that makes you think it’s likely the unloader over the engine?
K7 unloader can be finicky…….k1 seems to be the better option in my opinion. Try a trapped unloader on there to see if it makes a difference, can’t go wrong with them.
Bad gas can cause a lot of issues with engines, but I doubt it has much to do with what you are experiencing, unless you are also noticing the engine bogging down when this happens.
Is the unloader on a block or the pump? Have you tried adjusting it back to the correct pressure? I didn’t tighten down the bolt on my K1 enough when I first got it and after a few jobs noticed the pressure dropped… I think the vibrations caused the bolt to work it’s way down… not sure, but I put it on a unloader block and tightened it down more and haven’t had an issue since.
I had previous issues that I think were related to bad gas recently. I had a spark plug fail at about 20 hours which I think was from that but I can’t be sure if it ever got past the inline filter. Just for peace of mind I plan to check out the pump and carburetor but I appreciate the information!
I do have the unloader mounted separately on a block and I can understand vibrations making an impact but I drew a vertical line on the bolt of my unloader after it was set as I wanted to be able to identify if it was tampered with or something and it hasn’t moved that I can tell. I considered adjusting it up but I didn’t know if that would be a problem if it was another problem and I fixed it.
I will look into the k1 as well as an option. I went with 7.3 because I was told it was a more reliable pressure. I don’t know much about the effects of an oriface based unloader or sensor based and my thought (which I have little experience to back) was to avoid sensors and that an oriface would be more consistent?
Bad gas can definitely foul plugs and you would notice the engine having issues while starting or running… but I’m not sure what this means… what inline filter are you referring to and how would a spark plug make it anywhere near it? Worst case scenario the plug could crack and bits end up in the crankcase housing, but you would have bigger issues then just low pressure if that was the case. If the engine isn’t misbehaving when this issue is happening, the gas is likely not part of the problem.
Smart, I’m just trying to rule out things. You can always try adjusting it just to make sure, might have made a complete 360 so the marks are lined up, but it’s lower pressure… either way it’s simple to check so might as well rule it out.
I’ve read the opposite, it seems that the K7 has more issues especially when using the wrong bypass diameter… like @Kentucky1234 said, they are finicky.
Again not sure what your referring to… both are flow sensitive unloaders and both have orifices. I believe with the k7 you can just get different sizes based on the GPM of your machine… but I’ve only ever used k1’s so I’m not sure.
Bad gas can definitely foul plugs and you would notice the engine having issues while starting or running… but I’m not sure what this means… what inline filter are you referring to and how would a spark plug make it anywhere near it? Worst case scenario the plug could crack and bits end up in the crankcase housing, but you would have bigger issues then just low pressure if that was the case. If the engine isn’t misbehaving when this issue is happening, the gas is likely not part of the problem.
There is a plastic fuel filter between my gas tank and my GX690, i know that the bad fuel made it to the filter but i am not sure if it made it past that into the pump or not. Since changing the spark plug I haven’t had start issues but it does look like my exhaust isn’t outputting as clear and there is a small amount of soot coming off of it that i didn’t have before.
Smart, I’m just trying to rule out things. You can always try adjusting it just to make sure, might have made a complete 360 so the marks are lined up, but it’s lower pressure… either way it’s simple to check so might as well rule it out.
I’ve read the opposite, it seems that the K7 has more issues especially when using the wrong bypass diameter… like @Kentucky1234 said, they are finicky.
That makes sense, I’ll look into that in the morning. hopefully Its still usable until the replacement makes it in. I looked into the ZK1 and it seems to make sense to go that route for a lot of reasons in the future.
Again not sure what your referring to… both are flow sensitive unloaders and both have orifices. I believe with the k7 you can just get different sizes based on the GPM of your machine… but I’ve only ever used k1’s so I’m not sure.
I must have mistaken the difference, for some reason I initially thought one was flow activated and the other was pressure activated. my mistake!
I will update again when i have done a little more testing tomorrow and made the unloader adjustments.
I did a bucket test to determine flow and am getting slightly over 8 gpm as expected from the pump. I am only pulling 1500 of the total 3500 psi through the unloader with a red tip on it for testing. I am pretty confident the unloader is the culprit at this point. I re-set the unloader starting fully clockwise and then I went about 5 revolutions clockwise and then slowly dialed it in until I had high flow and very little trickling out of the bypass. the fluctuation isn’t happening like I had before. It’s consistent in flow but lower pressure than expected.
Unfortunately I wasn’t able to get video of troubleshooting because I am testing on my own and don’t have a bipod or anything for my phone currently and needed both hands.
I think you’re doing it backwards. You turn it in all the way (clockwise) then back it out incrementally counterclockwise until you get the desired PSI.
Maybe my K1 is set wrong but I have zero bypass when on the trigger.
Thanks I think I just forgot to put counter on the second time I said clockwise. I did start off nearly fully closed and then backed it off that way until I had a tiny trickle. Thanks for the correction. I am still waiting on my replacement unloader to come in. I replaced the starter and carburetor today to clear up any concerns about the bad fuel and that went well. I am hoping it’s an unloader problem and not the pump. I know I am supposed to tension the belt at like 100 hours but I am going to check it tomorrow just in case. I was also considering opening up the pump to make sure the check valves are in tact and working. Not sure what else to check that might be impacting things at this point.
