Air Pressure Constantly Changing

I use a Lowe's 60 gal 3.7hp 12cfm@90 it runs my lph just fine. It does not run continuously to keep up. Just sprayed single stage on 22' truck frame last week.
 
I have the C-Aire listed in one of my first posts. I'm not saying it's a top of the line compressor, but I'm pretty sure it isn't junk. It was roughly $1k, at cost. I have an automatic drain, a 1" Aquacheck & Coalescent filter at about 15-20 feet, and a 1/2 or 3/4" (can't remember) at my drop after another 50 feet down the line. My compressor is mounted outside in a shed, so I'd imagine that has to help the temperature of the air as it enters the building. During the summer, maybe not so much. So... I'd like to point out right now that I haven't had a water problem at all, just the pressure drop. Down the road I'd love to get a rotary compressor with a dryer, but that's just not in the cards right now. I'd love to have everything that's the best right now, but I can't. I have to make do with what I have. Profit is going into fixing up my shop, but this is an after hours job, not a full time thing for me. I have a wife who is a stay at home mom and 2 kids, my money isn't all mine.
 
when does your pressure drop happen? before the compressor kicks in or after? if after and your compressor can't keep up then it could be a bad valve in the compressor.

you need to record and keep the recovery rate (time it takes to pump up from start to stop) attach it to your unit, I check mine every other month to keep an eye on any problems but so far never had any (knock on wood). if the recovery is slow you probably have a bad valve. If you don't know what it should be call the manuf. and they can tell you.

If it starts hard on it's cycle you have a bad unloader, meaning it is starting under pressure. there is also a one way check valve at the spot where your compressor line enters the tank those can go bad also causing leak back into the compressor head which could cause hard start and air loss.

Rotary screw? not for me very, very, very expensive and repair bills are ungodly, no real need for this kind of work.

Reed valves are prone to crapping out along with head leaks which cause slow recovery.
 
Thought I'd update this. I had a couple things change, and it seems to be working now. First, I had added a wall regulator, more for keeping my air tools at 90 PSI than anything. I have kept it at 90 PSI when spraying, more out of laziness than anything. Second, I found out my gun regulator wasn't working. I though it sounded like hardly any air was coming out, and I needed 40 psi on the gun gauge to get anything to spray right. Swapped with my LPH80 gun regulator (cheap Eastwood replacing the expensive Devilbiss regulator) and sure enough, it sprays a thousand times better. What's odd is that I could plug in either the LPH80 or 400 and both would read the same line PSI, both would zero out when disconnected, but on the LPH400 it was inaccurate when spraying. Even more odd is that the gauge is after the valve, so apparently the gauge has a dead spot between 0 & 100psi....

Anywho, now my air pressure stays the same while spraying and no matter if the compressor is running or not. Not sure which problem was a problem.
 
This reminds me about 2 years ago the regulator that came with the devillbiss plus that I bought in 2005 wouldn't allow more than about 20 psi so had to replace. Got about 10 good years from it.
 
most regulators are not accurate for shit . especially at low pressure. i bought the reg from iwata for my guns. big difference.
 
Good to know Shine, after spending decent money for the Devilbiss, I'm hesitant to assume price relates to quality on these. Especially since my Eastwood one is twice as old and at least 1/3 the cost. They are both digital, I "reset" them when they are disconnected to make sure they are somewhat accurate. I've needed another one for quite some time, I'll have to grab a couple Iwatas.
 
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