Why does my crane boom only go up, even when I select boom down?

[Elizabeth Williams]

I'm working on getting an older crane back into service and ran into a strange boom issue. The boom raises normally, but when I move the control lever to lower the boom, it still goes up instead. When I first got the machine, adding weight to the hook block helped the boom come down. This time I tried adding even more weight, but it made no difference. The boom still only wants to go up.

 

[sulababa]

Sounds like the boom raise circuit may be staying energized or the control valve is stuck in the raise position. I'd start by checking the boom up/down solenoids and verifying the valve spool is actually shifting when "boom down" is selected. Good luck tracking it down!

 

[Fairy]

It sounds like either a bad control valve, linkage problem, or possibly a problem with your load holding valve. Since loading previously helped, I would recommend checking out these areas and ensure that the valve spool is free to move.

That's another reason why I like Boom & Bucket—there inspection sheets will help to spot hydraulic problems before purchase.

 

[jagatlalon]

A crane boom that only raises but won’t lower when "boom down" is selected could be caused by a hydraulic valve issue, an electrical control fault, or a safety lock preventing downward movement. Checking the control signals and hydraulic system would be a good place to start.

 

[mdsawkathossenraihan]

I agree with sulababa, that definitely sounds like a sticking directional control valve spool or a bad solenoid. On an older crane that's been sitting, it doesn't take much debris or varnished oil to cause a spool to hang up. I'd definitely check whether the valve is actually moving when someone operates the lever to narrow things down first.