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Cat 330D slow hydraulics

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HeavyJ

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We have a cat 330D that one day just started slowing down. Still has power just moves slow if you run two functions at once, mostly trying to raise the boom while moving something else or while traveling. Pilot pressure is 600 at pump & doesn’t drop no matter what functions are running. Main pumps both max out at 5000 when bottomed out but will only hit around 2500 when traveling & trying to lift the boom, like it’s not being pushed hard enough. No codes or events in ET but when watching live data everything looks ok except one value, boom up pilot pressure switch. No matter what we do it never goes high, stays on low. We have tried to find this switch to test it but local cat dealer & several techs can’t tell us where the switch is on the machine! We have a 330C & it doesn’t have this value. Hydraulic filters & oil has been replaced with no difference. Replaced check valve in pilot manifold & accumulator test good. We don’t know what else to check.
James
 
Nige

Nige

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I've sent you the schematic.
TBH I think the boom up pressure switch (or the input from it to the ECM) is not used on your machine. Tracing the G973 Orange wire backwards from Connector J1 Pin 48 it appears to get to CONN 12 Pin 9 then disappear, as there is no connecting wire on the other side of the connector. That could explain why the ECM does not see a change of state of that switch - there isn't one.
 
H

HeavyJ

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Grandview, TN
Thanks for the help! Now that we’re not chasing that ghost, the only other lead I have is the pilot accumulator. The one on the unit is sealed so we can’t test the pressure charge & we got a new one that came uncharged so we trying to get it charged. We run the test of lifting the bucket 3 feet then kill the motor & turn the key back on, then see if boom will lower in the first 20 seconds. Sometimes it does & sometimes it doesn’t. If it doesn’t the accumulator is supposed to be bad. Don’t see how a bladder type accumulator would work sometimes & not others.
James
 
John C.

John C.

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The accumulator is only to lower the implements to the ground if the engine dies. It has nothing to do with the performance of the machine. Have you checked the easy things first? Air filter on the engine, fuel supply to the engine, active and stored fault codes shown from the monitor panel and any event codes. I don't recall if the D models had DPFs but if so is that working properly. Has it ever been removed and cleaned or replaced?
 
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HeavyJ

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Grandview, TN
The motor was just put back in about 10 hours ago, all the filter were changed. I had the motor out to change the camshaft. One of the followers had turned 90 degrees & ate the lobe. Went back with the updated followers. No DPF on this unit, from turbo straight to muffler, which is new because the old one was rusted out. No codes or events stored either. The motor still has power, digs strong too just moves slow.
James
 
John C.

John C.

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Power on an excavator is measured in terms of speed, not hydraulic pressure. Has the machine worked properly since you put the engine back in the machine?
 
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HeavyJ

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Grandview, TN
Yes it was working great. Operator said it just slowed down while he was digging. He ran it a day like this & it’s constant, just slow. We brought in another machine because it was taking too long to load the 730s.
James
 
John C.

John C.

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Have you checked turbo boost when doing a boom up cycle time.

From what I have read from your posts, your problem can be defined on two paths. The engine doesn't have enough power for one. The pump is not putting out enough flow for the other. Put those sentences on two different pieces of paper and under each sentence write down the possible causes for each. Then start confirming or eliminating those possible causes until you fix it. It is how the troubleshooting cookbooks are put together in service manuals. Do you have a service manual?
 
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HeavyJ

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Grandview, TN
No manual, we’re going through Cat sis. The engine is running good, I'm more concerned about the pump volume. When bottoming out the boom I get 5000 psi on both sides of pump but when traveling & raising the boom it will only hit 2500 psi. So it either doesn’t have the volume or the pilot isn’t pushing it hard enough. Don’t have anything to test volume. It got slow all at once though so I wouldn’t think the pump crapped all at once & didn’t get worse after running it for a day.
James
 
John C.

John C.

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So if you want to go down that path, I would start at the simple stuff again. Check your case drain filter for debris. Check your hydraulic return filter for the same. Did you have the pump out of the machine with the engine or did you leave it in the machine hooked up and hanging? Could a piece of debris be the cause of your problem. As I recall these unit use negative control from the main control valve to stroke up the pumps. Could there be a problem in that? Can you check negative control.
I've not had to repair one of these but I believe there is a pump control solenoid and a way to view the current flow to that in the monitor panel. How many hours are on this machine? In my experience, these pumps are dependable to around 6,000 hours. Chances of problems go up after that. I would also suggest that a service manual is part of owning and operating any machine. Digital copies can be had in minutes and prices are reasonable in terms of down time and head scratching.
 
Nige

Nige

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HeavyJ said:
When bottoming out the boom I get 5000 psi on both sides of pump but when traveling & raising the boom it will only hit 2500 psi.
Click to expand...
Maybe worthwhile pointing out that the pressure you measure with a cylinder moving is going to be lower than what you see when the cylinder is at the end of its stroke. The pressure when moving is the minimum required to overcome gravity, friction, etc, etc, and will be way lower than the relief valve setting which is what you measure with the cylinder (or travel motor) stalled.

Here's a thought. Try jamming a track by putting a large towbar pin between the track chain and the sprocket. Test the pressure again with the track not moving and see what you measure.
 
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HeavyJ

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We changed all the hydraulic filters again & even cut open the pilot filter to check for debris, all was clean. We pulled the pump with the motor & capped everything off. It could have gotten something in the system though. Not sure about the negative pressure, never had to get this deep into one yet, will have to read up on that. I did read about calibrations. The batteries were cut off for a few weeks & the ECU was off the motor & sitting in the cab. It ran great for around 10 hours though, if the calibration got spiked it should’ve run slow from when the motor was first put back in. The unit has almost 12000 hours on it. Do you think running the flow calibration would help? I can’t test anything right now because we had to rob the stick cylinder hose to put on the 330C, we got lots of problems right now! As soon as I get a new hose I’ll start checking again.
James
 
John C.

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The issue with a load sensing system is that the output curve is reduced as pressure rises. Putting the system over relief reduces the amount of horsepower pulled from the engine where as a maximum flow at medium pressure will pull the most horsepower from the engine. The track functions will pull a little more horsepower when over relief than the implements only because those functions are set at a higher flow and relief pressure but they will not pull maximum flow from the pump nor maximum horsepower from the engine. Plus locking up one track will only load one pump.

I don't know if Cat still has the pump output curves in the service manuals anymore but if you can pull one up, it becomes clear.
 
Mobiltech

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If you just had the engine out I would start with checking engine rpm signal. An improperly installed speed sensor will not throw a code but may be giving false engine rpm. I would also be doing a prv calibration to see where the pump control is at.
 
M

Mbar

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I can as about to say prv sweep test and inspect filters. Got a call from a customer one time. For slow function on a machines. Told him to check filter in tank. When he did it was wearing a red fur coat. Pump was just off by a different mechanic while my truck was down. He is a friend so I’m not pointing fingers. Bottom line like said before. Start with easy stuff and you may find your problem. Also flow test is not hard on these machines.
 
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