CAT 330D L Hydraulic pump loading up and lifting boom causing no start

[Zac93]

Hey guys any thoughts on the following issue. Working on a 330D L Japan Market machine RDA, the equivelant SN is NBD

The fault started with the boom lifting on its on at all times while the engine was running, the operator was able to still lower the boom using the controls. This happened in the morning during operation and then when the machine was shut off for lunch it would not start. It cranks slowly, doesnt start(about 60rpm is to slow to fire i beleive) and as it cranks the boom lifts.

As it cranks the drive pump is reading pretty much zero pressure at the test port. it is loading up the idler pump, generating at least 1000psi, as the pressure increases the engine slows further until it stops due to load exceeding the batterys ability to supply power.

Checked the spools, found them to not be stuck and found the springs not broken etc. Removing the spool caps and then cranking the machine shows no movement in the spools. This tells me the oil is not getting to the boom through the normal passage. But I could be wrong.

We also disconnected the pilot pump to isolate any pilot cross feed with no change to the issue.

Has anyone had any issues similar to this or has heard of anything? We would like to pinpoint the issue before pulling the valvebank etc

 

[John C.]

Shut the machine off with the boom in the air and see if the boom drifts down. If it does you can usually hear the hiss from where the oil is leaking by.

 

[heymccall]

2 pumps and 2 boom spools.

 

[Gary Layton]

Good description of the problem. I'll be curious to hear what's happening.

 

[Zac93]

Shut the machine off with the boom in the air and see if the boom drifts down. If it does you can usually hear the hiss from where the oil is leaking by.

Good thinking, It's drifting quite slowly, the ram seals look very poor so I was assuming it was in ram. I'll have a listen

2 pumps and 2 boom spools.

Yeah it only appears to be Boom 1 spool which is on the affected side of the valve bank

Good description of the problem. I'll be curious to hear what's happening.

Thanks

Has anyone ever had a negative flow relief valve get stuck closed? I've sort of overlooked that possibility. Given the condition of the machine I can almost guarantee contamination will be the root cause where ever it ends up being.

 

[Zac93]

Just a bit of a conclusion to this thread

Pulled out all sorts of spools, checks and reliefs on the side of the valve bank with the issue. Found plenty of contamination and wear all over but nothing conclusive

I ended up winding off the main relief fully which allowed me to start the machine due to all flow just heading back out the valve bank.

Once I did this I ran the machine for a bit, ran all functions with pilot controls without any movement of machine due to lack of ability to build pressure. Then Wound the main relief back up to normal and the whole machine returned to normal.

Really have no idea but I just put it down to contamination, lack of PMs and oil sampling.

Anyway maybe this will help someone one day.

 

[Vetech63]

Did you install a new return filter in the tank after all this?