LeRoy Dresser won't stop making pressure

by Keith
(Ontario Canada)

I have a 1979 LeRoy Dresser 160 cfm gas vane pump compressor, it's been working just fine for years till the last week or so I noticed the pressure regulator on the machine wasn't holding pressure as steady as it use too or at the pressure it was set at ,it was about 20 psi higher.


Now it makes pressure way to high 140 to 150 PSI ( I have had the safety valve blow off once so far ) but now it keeps producing pressure even with the air outlet valves closed, and it won't let it idle down when not under load and it keeps bogging down and stalling the engine.

It's cold as hell here right now and I was told it might be moisture in the lines that froze but I have had it inside a heated shop for days now and its still doing the same thing.

Is this a unloader valve issue or a regulator issue or something else ? I'm not even sure where to begin.

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Jan 11, 2017
LeRoy parts
by: Doug in s.d.ca

Keith -

Thanks for letting us know what you found.

As to parts, it's a lot like finding parts for old cars. If there's a place like rockauto.com for compressors, I've not found it.

Good luck finding or making what you need.

Jan 10, 2017
found the problem
by: keith

I found the problem it was the rubber diaphragm on the unloader valve that controls the air intake into the compressor.

It was leaking a bit and that wasn't allowing the intake valve to close properly building higher pressure, once it ripped and would not hold any pressure it would not allow the intake valve to close at all and forced the compressor to build pressure uncontrollably till the engine stalled or the safety pressure valve blow off.

I found the issue and fixed it but now I found another issue, parts for this unit are hard to find and VERY expensive, does anyone have a good place for repair parts for old Le Roi's ?

Jan 09, 2017
LeRoy Dresser won't stop making pressure
by: Doug in s.d.ca

I don't have detailed knowledge of this machine, but you can forget the regulator, at least for now.

You want to find out why it's not unloading and idling down.

There's some pressure sensor that's supposed to tell the unloading system to disengage the engine, and at the same time let the idle drop.

Your issue would likely be either the pressure sensor is not working, or that whatever it connects to is is either disconnected, or failing to do its job.

I'd check any external linkages for binding and hoses for leaks.

Maybe you can post some pix of the thing? You'd have to start a new post to do that. Bill can pull them together with this one, if you do.

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