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by Lee(Burgaw, N.C. )

Fading Pumping Issue Quincy 325 – after a while it stops pumping on an older Model 325 2 cylinder piston air compressor. It has given years of good service but recently has started doing something strange.

Quincy 325 Air Compressor (photo: Www.yabe.chudov.com/quincy 325 Compressor/)
Quincy 325 Air Compressor (photo: Www.yabe.chudov.com/quincy 325 Compressor/)

It will come on normally when the pressure goes down, but after pumping for a minute or so, it stops pumping even though it is still turning.

It will do this for several seconds (8-10) and will then start pumping again. It will do this until it will eventually pump back up to cut off pressure.

I feel like there may be valve sticking but am not sure. I have cut it off until I figure out what is wrong and fix it.

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Hello Lee… given that I’m a bit slow on the uptake, when you say “It will come on normally when the pressure goes down, but after pumping for a minute or so, it stops pumping even though it is still turning.” what is still turning?

You might also want to check any belts for proper tension.

Please post a comment here with more info if you can.

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Fading 325
by: Lee

Mr. Bill,

The motor is turning the compressor at the same rate as it was while it is actually pumping, but it is not actually pumping air. The pump pressure gauge will spike, then fall and the pumping will resume without the compressor ever having stopped.
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Are you saying you are seeing a spike and pressure drop in the tank pressure gauge, or are you seeing it on the regulator gauge?

I would remove the intake filter, and feel the intake port – carefully – to see if a pressure variance occurs at the same time that the intake air flow varies.

I’m leaning towards a valve problem here, but not sure.
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Bad Unloader
by: Doug

The hydraulic unloader has gone bad..It’s the brass valve on the right side looking at the pump from the rear

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Fading 325
by: Anonymous

My 325 will stop producing air pressure if the oil level is low. Check oil in compressor. This is a safety feature.