M1084 crane hydraulic troubleshooting

Suprman · May 18, 2021

There is a lockout solenoid for each function. The crane movement like that controlled by the box on the side of the crane with the cable coming out of it going across the boom. Its called load moment.

Godspeed131 · May 18, 2021

Ok got it working my issues were both the boom up lock out and the boom down lock out solenoids plus the main two lockout solenoids are slowing down telescoping and hoist speed functions. With all the solenoids unplugged all functions are normal Hooray... now all I have to do is change out many leaking hoses. Thank you @Suprman for the help.

Mullaney · May 22, 2021

.
So I have to ask...

Has anyone ever found the elusive "ds maintenance" manuals of any sort for cranes mounted on a M1084 or M1089 ?

unix84535 · Jun 8, 2022

Godspeed131 said:
Yea I tried different heights, even fully extended. I do know the main lockout works as far as I know cause without the outriggers down nothing works but as soon as there down with weight every thing unlocks but the main boom will not budge.......I unplugged the lockout solenoids and the cable hoist feed speed has increased and my telescoping in and out has increased but the boom still will not raise. Also before I unplugged the lockouts I did notice the boom spool had a bypassing sound unless I messed with the mast controls then the boom handle would bounce and stop bypassing, thinking that maybe my issue is the actual spool itself possibly. With the lockouts unplugged I never had the bypassing sound with the boom spool

Don't knowif this will help but here is a link to a site that has the parts and diagrams for the FMTV-C M1089 BOOM MID SECTION AND TELESCOPIC CYLINDER REPLACEMENT/ADJUSTMENT (CONT https://trucks5tonm1083.tpub.com/TM-9-2320-366-34-3/css/TM-9-2320-366-34-3_424.htm

GTUnit · Jun 10, 2022

Solid thread. Im going to play with my M1084 crane this weekend probably.

unix84535 · Jun 10, 2022

Hope all goes well with the crane diag.

dk8019 · Oct 17, 2023

Bringing this one back up, mine is work across the board except for the retract function on the boom. With it in the retract position I think I can here a little bit of bypass, happening but it acts more like there's no pressure moving to the boom. I can retract it by reeling in the cable and pulling it back to the compressed position, but clearly not ideal. I do know the valve is doing something, as to get the cable to pull it in, I have to be in the retract position, otherwise it locks up good. The truck was outside for a bit, so I'll check the lockouts, maybe it's one of those, but any other ideas to explore?

Mullaney · Oct 17, 2023

dk8019 said:
Bringing this one back up, mine is work across the board except for the retract function on the boom. With it in the retract position I think I can here a little bit of bypass, happening but it acts more like there's no pressure moving to the boom. I can retract it by reeling in the cable and pulling it back to the compressed position, but clearly not ideal. I do know the valve is doing something, as to get the cable to pull it in, I have to be in the retract position, otherwise it locks up good. The truck was outside for a bit, so I'll check the lockouts, maybe it's one of those, but any other ideas to explore?

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My M1089 had a heck of a problem with "standing up" from the stowed position. Extending the boom, then rocking it back and forth made it work. Using LOTS of WD-40 on those two uprights finally made it start working as it should. You might spray a few cans of WD on everything that moves on the crane and see what happens... That would be a fairly cheap thing to try.

(Crane is similar but different)

M1084 crane hydraulic troubleshooting

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Suprman

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Godspeed131

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Mullaney

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unix84535

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GTUnit

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unix84535

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dk8019

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Mullaney

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