Ok this might turn into a longwinded post. My 320L started acting up last fall and here is what is happening. The left track is slower than the right, except when I activate another hydraulic like the bucket or thumb, then both tracks move at the same speed. When I move the dipper and swing at the same time, very very slow or one function doesn't move until the other is stopped. The left final drive tests ok according to the service manual (did a case drain test and all that). I've pinpointed it to the lower pump (I think). Also did some pressure checking and both pumps put out the required amount of pressure at all functions, it seems a flow problem. Btw filters are new. Does this machine have two pumps or just one main pump with two outlets. If that were the case I'd assume there was something plugged up at the main valves, as some functions work good and some don't.
Since you get the correct pressure the pump should be ok but the pumps give out flow based on a nfc signal, and that might incorrect for the stick/swing/left track side of the valve. You can compare that signal from one side to the other, you should see 2 small hoses coming from each side of the main control valve to the pumps, one connects on the top of the upper regulator and one on the bottom of the lower.
How do I compare the two signals. Try switching the lines? Thanks for the information.
put a gauge on them, one at a time is fine, they should act the same when you use a track. Lift up one track and check it on idle and then om high idle and then when you run the track at full speed. Then repeat for the other side.
I put a guage on both lines and there wasn't a difference between the two of them. Both ran at about 500 psi and when I moved a track it dropped down to 125 psi. I also tried dead ending the line into the guage and the same thing except the starting psi went up to 2000 depends on the engine speed.
Thats good then, I dont remember how it looks on a machine like yours but is it possible to swap the feed lines from the 2 pumps and then also the nfc lines? That way you can make sure the fault is in the pump or mainvalve. The 2 regulators are also identical and can be swapped over to see if the fault follows. If you look at the pump you have 2 square plates on the opposite end of the regulators, if you remove them you can see the piston that angles the pump inside, at rest they should be at the same depth, basically everything should look identical with only very minor differences. Pic, http://www.ladda-upp.com/bilder/24032/pumpreglering
ok I got it fixed. When I removed the covers on the regulators I noticed that all the bolts were loose and two were missing on the bottom one. I guess instead of the piston moving like it should the cover just moved in or out. There wasn't any leak or anything of the kind around that area. Put new bolts in and tightened everything and everything works fine. Thank you.
Nice that it was both simple and cheap then but odd it wasn't leaking anything.
That cover could move up to 18mm before it would leak. The oring seal isn't on the cover itself but rather on a long cylindrical plug that is on the cover and goes into the regulator.