After chasing down and correcting a few things in our search to find why we have low pilot pressure on our 1989 Sumitomo-built beast we've finally narrowed the last problem down to a bad pilot pump. We did this by blocking the line before the pilot filter and putting a test port there. Since normal pilot pressure is supposed to be around 600 psi we never got more than maybe 150 psi cold and had that drop to less than 50 psi when the fluid warmed up. The pressure bypass valve was determined to be good and not at fault. The two high pressure pump sections (#1 and #2) look good and put out around 5000 psi. I was told that the pilot pump (#3) at the front can be pulled without tearing the entire pump apart. I don't have an exploded diagram for the pump and was told that there is a "slip disc" and three O rings below the pump that need to be checked. When I inspected the pilot filter I found a tiny metal flake and grayish residue in the bottom of the filter housing, both of which seem to confirm the bad pump diagnosis. Since the previous owner had changed filters I couldn't determine if this was recent or just old debris. While I had that filter housing off I drilled and tapped the top of the filter housing for a test port to make future pressure testing easier. So now we're looking for either a good pilot pump or parts to rebuild ours once we pull the main pump. Our pump is the Uchida A8V115ESBR. I'm guessing that the A8V is the series and the 115 is the displacement? I was told by a firm in Puyallup WA that parts are scarce for these "older machines" though many have been used in the logging industry, particularly in the Pacific Northwest which is our neck of the woods. Any help or leads are most appreciated. Thanks, -Tom
Good day Lowahill A8V is the reference for original pump manufacture Rexwroth Germany no doubt Uchida build under some agreement, your pilot pump is not in the illustration as I see it but these normally take the form of a low pressure gear unit cheap and plentiful from may makers. Not sure about your test methods attached a bit of information that may help. Kind regards Uffex
Check with www.flinthyd.com
As always your reply aand advice is most welcome, uffex. After eliminating any bypass possibilities from the control valve and accumulator downstream, we narrowed the pressure check down to the pilot pump output by blocking flow to the filter and ensuring that the pilot bypass valve was operational. Pressure did not change noticeably with engine speed and was highest when the fluid was cold. As I understand it the pilot pump is a relatively simple fixed displacement gear pump with a cartridge-style relief valve that returns excess flow to (in our machine) the suction side of the main pump body. We have normal high pressures from pump sections #1 and #2, but all symptoms of low pilot pressure point right back to the same conclusion of a bad pilot pump. As I noted in an earlier thread the machine ran low on oil due to a bad rotating coupling for the previous operator. Enough fluid was put back in to move the machine about 350 feet over to where it has sat for around 6 or 7 years. The debris found when inspecting the pilot fluid is enough to convince me that we have to repair or replace the pilot pump. Pulling the main pump's 260 lb bulk doesn't look that much of a challenge as we have the access, tools and a backhoe to rig and pull it out, then take it down to my shop for the teardown. I'll check out some of the parts sourcing links that I've gotten with high hopes that we can soon be getting the beast back to work at the mine. Thanks again, -Tom
Thanks Vetech63! -Tom
If they cant help, there is another possible option. www.etshydro.com
I'm feeling encouraged! Thanks again.