Hydraulic testing

Looks like they haven't changed much. Looks like a fixed displacement piston motor on the blower and looks like a variable displacement piston pump. Looks like there's two pumps piggybacked?

Hard to say 100% how its all connected without a schematic but I wouldn't really be leaning towards a motor issue as of yet. If those fixed displacement motors are getting oil they'll usually work. I can't say I've ever seen one work and then not work intermittently like that.

Can't quite remember but I don't believe the blowers start the moment the PTO is engaged, there's a control valve to turn it on/off, correct?

 

If my memory is working then I believe the pump I've circled is the pump that runs the blower, correct?

If that is your blower pump I circled, if you followed the 2 lines on the RH side of the photo, on the clean and lightly rusted section. Where do they lead?

 

Looks like those lines attach this unit on the pump:

 

I would start with checking that those lines are pressurizing when you actuate the control lever. I'm not sure if those lines will contain charge pump pressure or system pressure so I would err on the side of caution and start with a gauge capable of handling max system pressure, which could be as high as 5 or 6 thousand PSI. In those cases I'd start with teeing in my 10,000 PSI gauges and see what happens. Tee a gauge into each line at the same time if possible to save time.

Take your readings while the blower is failing to start as well as when it finally starts before you pick a gauge more suitable to the actual pressure reading. Really easy to explode a gauge if you start out too small.