# Graco Ultra Max ll 490



## procraft (Jan 26, 2010)

Just recently purchased a used Graco 490. I have been using it anyway for the past few months, so I figured I would go ahead and get it. Just finished repacking it day before yesterday. I used it yesterday. It sprayed fine with no hard lines or tails, but it never would stop pumping unless I back off the pressure knob. 

I followed everything exact, even taking the advice of a graco rep that repacks them all the time and torqued the nut after the assembly was inside the cylinder. The packings were soaked for and hour in non detergent 30w oil. Any ideas as to why its not stopping? Thanks


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## NCPaint1 (Aug 6, 2009)

procraft said:


> Just recently purchased a used Graco 490. I have been using it anyway for the past few months, so I figured I would go ahead and get it. Just finished repacking it day before yesterday. I used it yesterday. It sprayed fine with no hard lines or tails, but it never would stop pumping unless I back off the pressure knob.
> 
> I followed everything exact, even taking the advice of a graco rep that repacks them all the time and torqued the nut after the assembly was inside the cylinder. The packings were soaked for and hour in non detergent 30w oil. Any ideas as to why its not stopping? Thanks


Bad pressure control, or bad prime valve....does it leak out of the return hose at all?


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## procraft (Jan 26, 2010)

NCPaint1 said:


> Bad pressure control, or bad prime valve....does it leak out of the return hose at all?


Will have to get back with you on if it's leaking out of the return hose. If it is you think it would likely be the prime valve gone bad?
I will get back with you later this evening about the return hose. Am in the middle of moving and the sprayer is at my other house. Thank you.


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## procraft (Jan 26, 2010)

Sorry it has taken so long getting back, have been covered up with work and trying to fit moving in at the same time.

If paint is leaking out of the return hose it is just a little. I pulled the return and while the pump is pressurizing a small amount of paint runs out. Can't tell if it's just paint that is already in the hose from sitting in the paint bucket or if it's leaking. No matter how long I let it sit there pumping, if I have the pressure turned all the way up it never stops running and a small amount of paint runs out of the returns hose. 

If you turn the pressure knob down some, it will stop pumping and hold it there. It's like it will maybe pump up to 2800 to 3000 PSI but never makes it to the 3300 like it's suppose to. 

Here is something else that happens every once in a while... I have gone to some jobs and plugged the sprayer in and nothing happened until I pull the cover off of the control box and wiggle the wire for the pressure switch that connects to the board, then it will come on and start pumping.
Thanks!!


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## Wolfgang (Nov 16, 2008)

Check the prime valve, and it sounds like the control board is on its way out. Both are somewhat common on Graco pumps.


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## mr.fixit (Aug 16, 2009)

sounds to me like you have a seat problem. prime and pressurize the unit and when it continues to run turn down the pressure control knob slowly until the piston is just drifting either up or down. if the piston drifts up the seat in the piston is messed up , if the piston drifts down remove the inlet seat inside the foot valve and flip it over as they are reversible. try that and advise


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## procraft (Jan 26, 2010)

Thanks.. I will check it tomorrow and post back.


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## procraft (Jan 26, 2010)

I primed and pressurized the pump and the slowly turned down pressure knob until it started slowly drifting. What it's doing is the piston raises up slow then fall on the down stroke fast. I would guess that would mean it's drifting down. Is the valve you are talking about called a base valve?


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## NCPaint1 (Aug 6, 2009)

repack it. Check the piston for any scratches, also check the inside of the fluid section or scratches. Both of those should be perfectly smooth.


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## mr.fixit (Aug 16, 2009)

sounds like you may have a problem with the outlet seat. that is at the top of the piston valve where the ball seats that screws into the piston. However NCPaint is also correct if your piston or the fluid section cylinder have any pressure cuts or uneven surfaces it will not hold pressure correctly. at any rate in order to inspect the piston valve outlet seat you have to remove the piston. that is why I like Titan and Spraytech you do not have to remove the piston to disassemble it. when you reinstall the piston back off the brass packing nut and insert the piston slowly and you may not destroy the new packings. put some grease t the top of the piston where the hole for the connecting rod is, that will help the rod go through the packings.


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## procraft (Jan 26, 2010)

I just repacked it. Did not see any scratches or anything like that in the cylinder or anywhere else. Mirror finish throughout the bore. I will disassemble it though and so I can check the seat at least. I have a bud that has a 490 that I could rob some parts off of if needed, like a new cylinder. Thanks for all the input on this.


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