# Graco pressure problem



## PowerPaintingUK (Dec 1, 2007)

Hey all,
I'm Phil & I'm in the uk where airless painting is a rare thing! I have been using my Graco 495 and had great results however the pump has developed a problem. I am reluctant to take it for a service as prices here are ridiculous, and I mean ridiculous-my 495 st maxII cost me £1800 (that's $3600!!). The problem is pressure control. When switching from prime to spray the pump just keeps going instead of reaching the desired pressure and then stopping & holding. I have to switch off the pump and release the pressure. I have just re-packed but that didn't help. This unit has only been used for approx 18 hours in the last 2 years. I'm thinking it's the prime-spray switch or perhaps the pressure transducer? What do you guys think? You're much more experienced in airless spraying than UK painters & like I said, I dont want to be any more ripped off with stupid prices if I dont need to be. Thanks for help/advice you can give.


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## firemike (Dec 11, 2005)

Hi Phil,

Could be the pressure switch... But then, when it's pumping and the selector is in the spray (pressure) position, does material leak out the small primer tube? If so, the Prime/Pump valve has a problem. A third problem might be a stuck check ball not letting the pump intake seal against the pressure stroke, forcing the paint back down the suction tube.

You will have to do a little exploring to see if material is coming back out one of the tubes. Seems like if it was a pressure switch and there was no material leak, the motor would stall after a short while because of building deadhead pressure, or a hose/fitting would pop.

Good luck!


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## PowerPaintingUK (Dec 1, 2007)

firemike said:


> Hi Phil,
> 
> Could be the pressure switch... But then, when it's pumping and the selector is in the spray (pressure) position, does material leak out the small primer tube? If so, the Prime/Pump valve has a problem. A third problem might be a stuck check ball not letting the pump intake seal against the pressure stroke, forcing the paint back down the suction tube.
> 
> ...


Well Mike, the ball shouldn't be sticking as it's spotlessly clean and brand new after the repacking. There is no material coming back out of the tubes, the pressure just builds up in the system and I have to switch it off quickly before something bursts. When I then move the prime/pump switch back to prime alot of built up pressure is released and alot of material shoots out of the small primer tube. If I just keep the trigger pulled the machine will keep on spraying (but obviously at very high pressure) and the digital display doesn't show a pressure reading at all. When switched to prime everything works as normal but when I then switch to spray the machine just keeps pumping as if there is no pressure limit to reach and there is not much change in the noise like there normally is when you switch to "spray". I'm wondering if it's the pressure transducer not reading the pressure and therefore the information isn't reaching the electronics which in turn isn't switching off the pump?? A new transducer here in the UK costs £125.00 + shipping which is $257!! so I really need to try and figure this out as best as I can before I buy new parts 
Any other thoughts? Mike?


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## Any Season (Nov 19, 2007)

I usually stick to Titan sprayers but I did have a similar problem with one of my 440i's earlier in the summer and I had it repacked, new prime switch, new ball, etc etc, and it turned out to be a $430 chip for the on-board computer that regulates pressure. As stupid as it sounds, if you are in a pinch try using a hammer and giving a few light taps to the piston housing and see if it catches, bc I also agree that it could just be the ball. One other thing though, make sure your service guy is using the right parts. I know for my Titan, I had a guy use bedford parts which I guess are aftermarket and dont quite match up all of the time. Your best bet is to take your sprayer to a chain store, like Sherwin Williams or whatever you have over there. They have to best service techs.


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## Workaholic (Feb 3, 2007)

Any Season said:


> it turned out to be a $430 chip for the on-board computer that regulates pressure


I had a similar thing happen to a 695 a couple years ago, 300 dollar chip.


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## PowerPaintingUK (Dec 1, 2007)

Thanks guys,:notworthy
I'll make a couple of calls on Monday morning and see if I can ask a couple of service engineers what they think it is. Sounds more and more like the pressure transducer. Hopefully it wont cost me too much. I appreciate the replys:thumbsup:

Phil


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