Good info.
a. that fact that the pump is new and never worked before means it is likely the pump. If it had been worked before, and suddenly not working when only the valve was disturbed, would make it less likely.
b. the adjustment screw is the unloading setting. Basically, it is set to run both stages (max flow and speed) up as high pressure as possible until it runs out of engine hp. Then the large stage unloads to tank as I wrote above. Once you gt it working, you set it just that way: keep increasing the pressure setting until it bogs the engine just before unloading, then back off. Note: must be in resistance into the wood, and it may happen very quickly. Or, if the wood splits at below 800 psi, it may never unload and slow down. That is a good thing, you want as much speed as possible with as much pressure capability as possible.
c. It is not as though you are ‘not getting second stage’ because it doesn’t change from one to another, or turn off one and turn on the other. Both are added together for high speed, then the large section is unloaded. The small section that you see as ‘second stage’ was there all the time.
The fact that pressure increases with the unloading adjustment screw means that portion is working fine. I’ve just doubled my money down on the gamble that the check valve is not working, or maybe even missing entirely. since this is a new unused pump. I don’t have a cutaway, nor a pump at hand to check it, or I could figure it out on a glance.
My suggestion, pull the unloader cartridge out, careful not to cut the o-rings around the cartridge but it will come out like a spark plug. See what else is in there. Maybe you have to split the pump. Should be easy enough. My guess how I THINK it is built will be there is a ball and spring that works as the check valve. Follow the outlet port of the larger (wider) gear set. That is the large stage. Before that oil gets to the outlet port of the pump casting to the outside world, it should pass through this check. The unloading valve and the pilot signal from the small gear set will go off to the side somewhere, but the main flow from the large gear set must pass through a check. If it’s an open path, bingo, no check. If the spring is missing, or ball broken, etc. same story.
Haldex Barnes will have parts, but a precision bearing ball from an industrial supply house will work, as a standard round steel ball is what it is and they purchase it from the bearing industry. I am saying ball for check because it is the cheapest way to accomplish so that is what I assume they will have done. It could be a tapered cylinder shaped hollow poppet with the spring inside it, but my bet is on simple ball and seat.
And I will try again to post a schematic, but have no access to actual cutaways or pictures.
Trip, good point. I need a 13 gpm preferred or maybe 11 for another project. Many of the ones I have watched on ebay state they are new old stock, or purchased in large lot from vendor returns or obsoletes, some have Northern numbers form the 1980’s. Not sure what you are getting, and they sell within $20 of new price. One sold for $9 more then the new price listed in the same ad that is sold from! I don’t get it. If I can’t get it for half price, I’ll buy a new one exactly what I want from Surpluscenter. Home project is different, but can’t take a risk of poor quality for a customer project.
Anyway, take it apart and look for missing or malfunctioning check.
BTW, when set up to unload at 800 psi, did the detent valve work?
k