Hello, Caterpillar E120B, 1993. We recently had some fuel line/filter issues, but got it cleared up, we thought. I was moving some brush around yesterday and extending the stick began to stall the engine. Moving, swing motor, boom up and down, bucket, all unaffected. I don't remember whether the engine came back immediately or slowly when the controls were released. We're investigating whether the new Fuel line is kinked, and stuff like that. It's also about time for a hydraulic filter. It really felt like it's a possible relief valve failure. I'm not sure what kind of spools the thing has, but if it's center open, then it would rely on a relief valve if the stick were actuated? Any tips on troubleshooting? How dangerous is it to run/test in the meanwhile? Will I destroy the pump stalling the engine with it? The service manual is really expensive - if anyone can help me with some of the manual pages relevant, that would be great. Thanks! JB
Adding hydraulic oil made it run well for 2 hours. This sort of makes sense because maybe the stick cylinder is the highest and drained first?? Would the extra pump drag be from lack of oil / lubricant? Thanks
We had a 120B with similar probablems there was a screen near the injection pump been a while can't remember exactly where but it would idle fine and some times work for hours then all at once die down let it set start up and run fine. This went one for a while untill it was all the time then we found the screen cleaned it out and it ran perfect. Get a srevice manual it helps find hidden things we never pay attention to until it breaks.I know the screen was near the pump might be in it or a line. Good luck.
Thanks 06Pete! I looked for little screens in the banjobolts going into the filter, out of the filter, and into the manual pump, but didn't find any. the manual pump seems to work fine. would it be after that?
Can't recall as I have not had it in about 7 or 8 years but I am thinking it was on the pump. Either where the line came in or just unscrew a cover off on the pump I can't remember.I know it was after the filter. I hope that helps.
If boom up is unaffected, forget fuel system - it's fine. Boom up puts as much or more load on the engine than stick out. Problem sounds hydraulic. I'd be looking at the stick drift reduction valve. I'd also be looking at the PRV function, making sure the pilot logic circuit is closing the implement logic switch when using stick. If adding oil makes it work, and you have this issue due to a loss of oil, then your hydraulic pump is trashed. That hydraulic pump can run without oil for about 90 seconds and then it's life is effectively ended.
Hello, I also have a E120B serial number: 6JF00483 that is having hydraulic problems also. When I stick out or swing everything works fine but as soon as I use both functions on that joy stick at the same time the motor will bog down or even stall. The main boom/ bucket joy stick does not affect the motor at all. If I am hearing correctly sometimes it sounds as if the motor has a slight load on it after I stop moving the joy stick. I changed all the filters and it did not help at all. This problem got worse over a 2-3 day span (at least when I begin to noticed)
What I am wondering about is internal bypassing on the stick cylinder. Operate several times and check that cylinder for heat. It would likely be very obvious if that is your issue. That will certainly cause the issues you are having.
Hello, my E120B, serial number: 6JF00483 has something wrong with left joy stick functions. When I stick out or in and swing I cannot feather it at all, it's instantly full speed. And when I let go of the joy stick, the stick in and out and swing stops instantly. This does not happen with booming up or down or with the bucket ether way which is on the right joy stick. If you have any thoughts please let me know. thank you