Speedaire 3Z428 bogging motor

by Jon Williams
(Grants Pass Oregon USA)

Speedaire 3Z428

Speedaire 3Z428

Speedaire 3Z428
Speedaire 3Z428
Speedaire 3Z428

New to me old (1970's-80's?) Speedaire 3Z428 1 Stage 2HP running on 110V.


I just bought this used and was told the motor was bad. But the unit looked to be in good original shape overall and was nearly free.

On closer inspection the motor appeared to be wired for 220V but was being run at 110V. I re-wired to 110V but it still barely ran. The bearings in the motor felt terrible.

I took the motor to a good local re-builder, and he deemed it "un-repairable".

I bit the bullet and bought a new Marathon 2HP motor with the same specs. as the original Dayton motor it came with.

I have thoroughly cleaned out the tank, and it is dry.

The pump wheel turns freely without any binding or anything that feels bad, but I'm not really sure what it should feel like. You can feel some resistance from the compression stroke of the piston but again nothing that feels like it would strain a 2HP motor.

With the new motor installed it runs fine with the main valve open and everything seems to turn fine and there's no ugly noises, etc.

But as soon as you close the valve and allow some pressure to build the motor starts to strain and get bogged down. I've only let it run up to about 50lbs. of pressure as I'm worried about damaging the new expensive motor.

My question is before I tear down the pump (which I do not think is the culprit), is there something in the valve control assembly that could be causing this? And how do I isolate and test this?

Thanks for you time, Jon

Comments for Speedaire 3Z428 bogging motor

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Jun 14, 2017
3Z428 bogging
by: Bill

Well done. Glad you got it worked out. Thanks for letting us know.

Jun 14, 2017
update
by: Jon Williams

I took apart all the fittings on the manifold, flushed the manifold out. Took apart and cleaned the main valve, and the diaphragm on the switch.

And now it works as it should builds pressure up to 125 psi and shuts off.


Jun 14, 2017
Check valve
by: Bill

Yes, there is, and I referred to it in my earlier response:

"With the tank empty pull the tank check valve and make sure it's not plugged. "

Jun 13, 2017
One way valve?
by: Jon Williams

Yes, power supply is fine and short 12 Ga. cable.

Is there a valve that keeps pressure from the tank leaking back to the pump, like a one-way valve?

It seems like there's too much back pressure at the pump?

I did read through the trouble shooting bits on this but I'm still at a loss.


Jun 13, 2017
Speedaire 3Z428 bogging
by: Bill

The typical culprit is a start or run capacitor. A new motor lets these out.

Good power supply, not too long a run?

With the tank empty pull the tank check valve and make sure it's not plugged.

Then, visit the troubleshooting page on this site, scroll down to the page about compressors that bog down.

Let us know what you found, please.

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