Is this a leaking air valve?

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PostPosted: Sat Apr 22, 2017 8:44 pm
I've got an LPH400LVX I picked up used a few weeks back. Initially it sprayed well but over the last couple of days there is an intermittent issue. I can get the gun set for use and at times during spraying the air volume will either drop out or increase dramatically at the cap. It happens randomly even with the air tank is full and the compressor isn't running. The air lines have been checked and the primer gun operates as expected. It's a copper plumbed pro grade air system with filters and adequate compressor capacity. The issue is in this particular gun.

I've tested the gauge at the gun (as well as separately away from this gun) also testing this gun with the gauge direct from the line on the wall removing the quick connect fittings and threading each connection (the fittings are high flow Coilhose). Same issue, can be laying down well then drop and sputter or increase and pelt the panel with material. When this happens I can slightly adjust the air valve control and the performance snaps back to normal. By slightly I mean not even a full turn and simply moving it seems to make a difference. I've disassembled the gun, the needle and fluid valve are clean and unobstructed. The air valve adjuster has seen better days as has the needle packing. The packing has a slight leak on the backside that I'll fix with a new part.

Would a failing air valve seat cause intermittent erratic air flow through the tool? Even if I had to throw $100 worth of parts at it I'm still well ahead. I don't want to throw parts at it without knowing a bit more about how it works.

TIA

Dave

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PostPosted: Sat Apr 22, 2017 10:46 pm
Dave,
Are you adjusting the air control valve on the bottom of the gun handle?
I have the LPH400LV and have never touched that valve. Adjustments made with air gauge mounted to the spray gun.
1968 Coronet R/T


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PostPosted: Sun Apr 23, 2017 12:06 am
I normally leave it wide open and use the gauge. When it happened the first time I thought it might be the regulator and I tweaked that and nothing then I moved the air controller on the gun to see what would happen and it popped back to normal. It could be a coincidence but I was able to do it a couple of times, though not every time.

After testing the gauge and looking at most of the rest of the gun, nozzle, needle, guide, related springs (except for the air valve and seal) I'm leaning toward the seals being old and worn. When I get back into the shop I'll pull the air valve and seal out and have a look at them. Both my Iwata manual and the manual for the Air Gunsa say the packing leak can change the pattern but this is a pretty catastrophic change in air pressure.

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PostPosted: Sun Apr 23, 2017 8:11 am
It sounds like you are on the right track then. I believe there is a spring and seal in there, maybe a washer too. Best to replace them all.
Hopefully that will take care of it.

I bought mine used and it just needed a real thorough cleaning and a new lid for the cup.
Worked fine ever since.

Another thing to check is that your tip is on tight.
1968 Coronet R/T


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PostPosted: Sun Apr 23, 2017 1:30 pm
Thanks. The O ring on the plastic valve insert has seen better days. Once I took the trigger off and started looking under there it's an obvious leak. For under $100 I got all the parts to rebuild the gun as well as the updated fluid adjustment knob with a better seal. Still under $300 for the gun and new parts. Except for the body, nozzle and needle it will be all new.

Dave

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