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Power for a Wayne – Leroi Dresser 440A Air Compressor

Published Categorized as Air Compressor Troubleshooting, Wayne No Comments on Power for a Wayne – Leroi Dresser 440A Air Compressor

by Chris Gockley
(Schenectady, NY, USA)

I have a Wayne Compressor with a Leroi Dresser pump model 440A. I bought it with a broken copper line (1″ with cooling fins) which has been repaired and no pressure switch. It has a 7.5, 1850 rpm) Marathon motor and an 80 gallon tank.

Leroi Pump on Wayne Air Compressor
Leroi Pump on Wayne Air Compressor
Wayne Upright Air Compressor
Wayne Upright Air Compressor

My only 3 phase power is through a 7.5 hp rotary phase converter which is unable to power this compressor. There is a 1/4″ plastic tube coming from the front (see picture) which I assumed is supposed to be hooked up to the pressure switch.

I bought a square D pressure switch (on 100 and off 125). I hooked the 1/4″ line to the pressure switch but did not hook up the electricity. Instead I powered the motor up with a magnetic switch to see how the rotary phase converter would respond. Not too good. It turned it over straining for about 5 seconds before the 30 amp breaker tripped.

I was pleased until I noticed that compressor oil was seeping out from the front of the compressor, through a small hole near the that 1/4″ fitting that I have run to the pressure switch.

When I turn the flywheel over by hand, oil is squeezed out of this small 1/16″ or 3/32″ hole. There is a short 5/16″ or 3/8″” set screw in front of this hole . The close-up picture shows oil seeping from the hole.

Can someone explain why the oil is being pressured through this tiny orifice? Is this because I don’t have the pressure switch hooked up and operational?

The compressor has excellent compression and the motor is fresh. Does the lubrication system rely on pressure from the tank through the pressure switch to redirect the oil flow? Any information would be awesome. Chris Gockley


1/4″ line
by: Roger

The port on the back of the compressor needs to be hooked up to tank pressure. It will send air to the heads to open the inlet valves to unload the compressor.

Right now it is hooked up to the pressure switch which is doing nothing at all.

You can either hook the unloader to the tank, or hook the switch to an unloader port on the tank check valve to unload pressure between the pump and tank at shutdown.

Either method will work fine, but the hydraulic unloader on the back of the pump will hold the valves open if there is no oil pressure, which gives an extra safety margin if the pump runs low on oil or is not building oil pressure.


by: Roger

That pump should only need a 5hp motor if it is geared correctly. It look like it has way too big a drive pulley on the motor. The oil leak may be from a failed diaphragm in the unloader valve.

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By Bill Wade

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