Ok, got a bit of a head scratcher here, need some knowledge and some ideas. I have a 325b, serial 325ba2jr03572. Lately when cold and I fire it up, the throttle doesn't control properly. Settings 1 to 10 on the display show properly when you turn the throttle dial, however when it is set on #5 and you move the stick control it revs to #10. If it's set in 6, it goes to 9. And if it's on 7 it goes to 8. The numbers on the display change and the engine revs accordingly. When you set it to 8, 9, or 10, it works fine, and same with 1 to 4. After it has ran for 15 mins all is good, and everything works fine. I changed the throttle control assembly about 150hrs ago, and everything worked fine afterwards until recently. It's has had me a little lost as to where to start looking. I'm going to start pulling connectors apart that I had apart doing the throttle control,and start looking for corrosion and moisture, but just thought I'd post on here and see if anyone had some insight into the problem. Thanks
One of our excavator experts will be along soon to confirm this but I seem to recall that if the throttle control assembly is replaced the new one has to be calibrated.
Sorry, forgot to mention, I have the service manuals for the machine and did the calibration after replacing the throttle control
It sounds like you may have a problem with the feedback circuit in the governor motor. Is it a one or two cable setup? Have you done the calibration routine for it? If it does turn out to be the problem, they're not really repairable and fairly pricey to buy I'm afraid.
Yeah, I'll keep you posted to what I find. The governor control is a single cable setup, and I had replaced it about 150hrs ago with a new one from cat. I just can't figure out why the throttle would jump up higher whenever I engage the stick hydraulics.
So you're saying the problem ONLY occurs when the machine is cold and then ONLY when you work the stick in and out?
Yep, pretty much. After running it for 15-20mins, it will work correctly.
Well that's a weird thing then. There's no electrical interface with the stick circuit and the EPC, (Note that Cat call the computer on older excavators the Engine/Pump controller, not ECU or ECM), in fact the only inputs from the hydraulic system are switches for implement pressure, travel pressure and boom raise. The only thing I can think of is the wiring harness may be rubbing against one of the stick hoses in the main control valve area and when the stick is operated, the hoses are flexing under pressure and causing a short or open circuit.
It's worth a look. It may be a couple days till I can get to it, but I'll pull it apart and let you know if I find anything as soon as I can
If the machine has OEM auxiliary hydraulics, as evidenced by a controller (with LED display) next to the air cleaner housing, water has entered and damaged the controller. My typical failure was incorrect rpms at several speed dial positions. The unit can be taken out of the loop by unplugging the controller under the cab floor, and connecting the harness as if the controller wasn't there. Very common issue on my B series Cat's.