Can bad hydraulic pumps make pressure spec?

Hey guys, I have a Hyundai 210 LC-3 with slow hydraulics. Filters are new, screen is clean, she's not too bad first thing but quickly slows down as she warms up. I figure the pumps are finished, especially since they've developed some external weepage, but when I check the pressure off them (cold and hot) they both meet idle and relief specs given in my shop manual. Is it possible for bad pumps to meet spec??

Well, the plot thickens. I think my pumps are okay, though I'm still very curious to have the title question answered.

I just found some tests in the service manual for the EPPR and performed them. The EPPR itself seems to be fine, however the signal it's getting from the ECU is not. It's getting too much juice and that translates to less power. The final nail was when I found and hit the prolix switch (it's the full system emergency override), she runs like a hot damn. The manual says the ECU is bad, but the manual also says it's located behind the seat when it's actually under one of the armrests, so it's not the most comprehensive thing on earth. I'm inclined to believe some input(s) is at fault before I condemn the computer. Any thoughts?

If it's working ok without the ECU then go for it, the bit of extra fuel burnt in a day won't amount to much. I worked a Samsung 210 with a fried computer for 2 years with no problems. The computer problem was dust had gotten into the box and shorted the whole thing out, a $6000 repair that didn't need doing. The agent would ring me every month saying it needed to be fixed. He said it would be justified because of the extra fuel burnt. My reply was I could do a lot of work for the extra fuel and have a reliable machine.

I'm inclined to agree. But does this sound like a fried ECU? I would've figured that a dead computer would mean a dead machine

12ValveHyundai said:

I'm inclined to agree. But does this sound like a fried ECU? I would've figured that a dead computer would mean a dead machine

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Need some clarification. Is it a ECU or PCU? The Samsung was to old for an Engine Control Unit ( old school Cumins) . The throttle control and engine stop still worked with the the electrical switches with the computer turned off.

All and none. Coming from auto mechanics I tend to use the terms interchangeably. There's only one main computer, manual calls it the CPU. Everything seems to work the same after hitting the prolix switch, other than it not being tired mule slow

Putting aside the pump controller, can you check according to your shop manual the signals whether hydraulic or electrical that controls and regulates the pump?
As for the pump, normally as long as it can build pressure to specs, no abnormal noises, the return filters shows no sign of pump metal particles, vibrations etc...
It's all good signs for a good pump but doesn't guarantee that the regulators for the pump are working properly, hence the checks of hydraulic pressures that controls the regulators according to your shop manual
I've never worked on your model of machine but would normally troubleshoot most excavators with these in mind...


Sorry, I just read your later posts and now realized you already came to the conclusion about the controller ... but do update us on how it goes...