# Can't get outlet pressure on my air compressor



## FileOpen (Jun 9, 2011)

I have a Porter Cable 150 PSI compressor. After turning it on, the pressure gauge gets to 150 PSI. I usually set the outlet pressure to 100 PSI.

I have not used it for at least a month. In that time, there was no outlet pressure. But I'll admit I did not drain the water.

Now when I turn the regulator to set the outlet pressure (to say, 25 PSI), the pressure gauge drops by 25 PSI. When try to set the outlet pressure to 50 PSI, the pressure drops again and motor goes on. I can't maintain pressure and the motor keeps going.

After experiencing the problem yesterday, I did drain the water and tipped the tank while doing so. Anyway I tried setting the outlet pressure again a couple times and this morning. Still no luck.

From what I've read, draining water is for preventing rust. Water doesn't seem related to achieving pressure.

What can I do ?!?

Thanks for reading.


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## Yodaman (Mar 9, 2015)

Are you loosing air when the compressor is running? There is a pop off relief valve that may be stuck open. Usually has a little ring on it. Pull It out and push it back in.

Turn on the comp., start dialing the reg. knob clockwise until the pressure comes up. If no luck, we may have a bad regulator.

When you turn down the operating pressure to a lower setting go past your desired set point and then slowly increase until reached. Backlash isn't the correct term but the effect is the same.


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## Bondo (Dec 8, 2007)

Ayuh,.... By-pass the regulator,...


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## Yodaman (Mar 9, 2015)

FileOpen said:


> From what I've read, draining water is for preventing rust. Water doesn't seem related to achieving pressure.



normally it isn't...................unless you left the valve open


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## fireguy (May 3, 2007)

FileOpen said:


> From what I've read, draining water is for preventing rust. Water doesn't seem related to achieving pressure.
> 
> .


If you do not drain the water, as the water accumulates in the tank, you have reduced the air volume. This can cause the compressor to cycle on and off. When you drain the tank, you should get water, then air spitting from the drain valve. If you do not get water/air, the valve is plugged with rust. Shut off the compressor and use a wire or other probe to break through the rust obstructing the valve. 

We often remove the drain valve and install a 90° elbow, then a nipple and then the drain valve. If the drain valve does not work, we use a 1/4 turn ball valve. The object is to make the drain valve more accessable, which leads to better maintenance. 

If you have a compressor with oil in the crankcase, change the oil yearly. We use Slick 50 in our customers compressors.


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## Thurman (Feb 9, 2009)

"I can't maintain pressure and the motor keeps going." This sounds as if the check valve between the actual compressor and the tank is stuck open. Try this: Bleed all air pressure from the unit. Back out the regulator adjustment all the way. Start the compressor, with nothing attached to the compressor, and watch to see IF the pressure within the tank rises. IF it does, the check valve is working. IF the pressure within the tank does not rise do this: *Remove the electrical cord from the outlet.* Drain *ALL* air pressure from the unit. Find the line, metal or rubber, that comes from the compressor unit to the tank. There is most likely a brass fitting attached to the tank, this will be the check valve. Remove the compressor line from the brass fitting. Remove the brass fitting/check valve. Wipe the fitting with a clean cloth. Attempt to blow air, as in blowing up a balloon, through the check valve at the end the line from the compressor was attached to. You _should_ be able to blow air through this way. Try blowing air through the check valve via the end that was in the tank. You _should not_ be able to blow air through this way. IF you can blow air through the check valve via the tank end then you will need to clean or replace the check valve. A check valve can be cleaned using something like carb cleaner or brake cleaner and another method of compressed air such as a can of computer keyboard cleaner. IF the check valve seems to be working properly then put everything back together. My next guess would be a bad regulator. To check this make sure the tank is completely empty of pressure. Make sure the regulator adjuster knob is all the way out. Plug the unit back into an electrical outlet and start the unit up. The pressure in the tank should start building up and continue until the unit kicks off at it's high pressure setting. IF this goes well then attach an air line to the unit and make sure that there is a fitting attached to the other end of the air line that will air to escape freely and that end is secured somehow. Then start turning the regulator adjustment know in until air escapes out the hose. IF air escapes out the hose continue to turn the adjustment knob in until it bottoms out. At this point the compressor should be running and the tank air pressure and the output pressure are the same, or close. Back off of the regulator adjustment knob and see if the output pressure lowers and the tank pressure starts to increase--it should. Once you have the adjustment knob all the way out the unit should build up to cut-out pressure and shut down. IF this happens then the regulator is fine. IF this does not happen they you would need a new regulator.


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## FileOpen (Jun 9, 2011)

Problem resolved. 

I had the compressor in the kitchen, the hose goes up into the attic where I'm doing work. The compressor's in the kitchen to avoid getting construction dust. Didn't know until I went in the attic that the palm nailer was connected and it was in some weird state where it was letting air out. After disconnecting the palm nailer, the compressor was able to achieve pressure. I guess that's why it's advised not to leave nail guns connected.


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## Yodaman (Mar 9, 2015)

FileOpen said:


> I guess that's why it's advised not to leave nail guns connected.



Draining your tank would be a secondary reason to disconnect when not in use. The primary reason is to avoid a accidental shooting. Similar to leaving a loaded firearm laying around. Glad you got it figured out without repairs. :thumbsup:


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## landfillwizard (Feb 21, 2014)

You can save a lot of time by just cracking the bleed valve just to let it hiss a little. This will allow moisture and air to drain out and keep the tank from rusting.


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