Hyd. Problem on CAT 426 rubber tire

[buckstalker]

I a Cat 426, 1988 or so model, 7BC1978 s/n and am having problems with a couple functions signaling the pump to stroke. My loader lift and backhoe bucket curl in. Both do work, but only if you perform another function simultaneously. It wont lift under load but curl also and it will lift. Same with the back bucket curl.

I changed all the resolvers in the last couple days. Had a boom problem and the resolver was bad, so when this showed itself, I changed all of them. Machine is 2wd and std front bucket. No hammer plumbing

Meanwhile working in some brush, I caught some wires and my neutralized no longer functions. The machine did have the electronic leveling but I threw it in the junk pile and there is a electronic connection on the loader valve. Coincidence with the neutralizer? I doubt it, but am really mnore interested in the hyd functions than the neutralizer, I can shift manually, no big deal.

Thanks

 

[oldnslo]

What do you mean by resolvers? I would suspect an issue with the load sense signal being lost since some functions work and some don't. Each valve section/spool should have two sense checks that supply a signal to the load sense line. If some thing has plugged this line they will not signal the pump to come on line and supply flow or pressure.

Not sure if Cat installed test ports in this line but they where usually pretty good about doing that. With no functions I would expect to see around 300 PSI in the load sense line. With a function active this pressure should rise to what ever is required to move the load.

Roy

 

[buckstalker]

The functions do work, until you load them, as though they are working under standby pressure but never send the signal to stroke.