Hi guys, I'm a long time reader, first time poster. Firstly this forum is great! I have a Cat 320C (2000 year) with 12,500 hours on the clock, engine still original apart from rebuilt turbo about 1000hrs ago, starts first time every time and blows no smoke. Hydraulic pumps were rebuilt at 10,000 hrs. Over the last 12 months the machine has been getting slower and slower to use, took a while to realise that the engine revs at throttle setting 10 were far lower than they should be, at 16-1700rpm. The rpm at full throttle should be around 2100 am I correct? When manually revving the engine by twisting the throttle on the injector pump the most we can get out of it is 1850rpm, the machine runs a lot better but nowhere like it used to. I'm thinking the injector pump needs servicing or rebuilding? All fuel lines are clear (incl. banjo fitting screen), and the machine is regularly serviced. It's not lugging down at all, just sooooo slow to use! Can anyone help? Regards, Glenn
What are you using for an accurate tach..?? the machine's tach?? not good.. get a hand held.. Its not uncommon for the injection pump governor spring to loose tension over the years BUT 400-500 rpm is excessive.. I'm thinking you have a ZEXEL inj. pump on the machine?? the full load rpm is usually stamped on the gov. nameplate.. If you get some #'s off the pump nameplate, I can tell you what you have.. IF it was just a couple of 100 rpms, I'd tell you to move the hi idle screw back about a 1/2 turn.. it will have a steel cap on it, that will need to be cut off.. Just MAKE SURE your hitting the stop screw at full throttle..
Last time I looked at a C model excavator it only turned around 1,850 RPM. Maybe someone here with access to that information can fill us in. If the throttle lever hits the stops on the fuel pump, that's all you have. If the machine is running slow at that point you should start checking the cheap stuff first. Air filter, fuel strainers, water separator and fuel filter should be your first thoughts. Do not start turning screws on the fuel pump. If the lever doesn't hit the stops, you need to re-calibrate the system. That can be done from inside the cab using the electronics in the monitor panel. Maybe someone here can fill us in on that procedure as well. In my experience the monitor displays for RPM on electronically controlled machines are far more accurate than any hand tach I've ever used.
Fuel and air is all good, the machine is never struggling, it's just really slow to operate, will barely track up a hill and all other functions are painfully slow even with no load! It's like the pumps aren't stroking up enough. Could something need recalibrating?
Are you hitting the high idle stop? Yes it could need a recalibration. Check the bolts in the lever going into the injector pump. It should have two 6mm bolts. I have seen thes get loose and not stroke the pump lever all the way.
Have a look at the attached pic, the machine is currently idling at 820 rpm, however the throttle controller is set at position 4, see the gap between the stopper bolt and the lever?
If I turn the throttle controller back to position 1, the revs drop so low the engine stops, it seems something is way out of adjustment somewhere
Also just found out that machine has blown a head gasket.... Will have to replace that tomorrow before anymore rpm issues can be addressed!
The 320c only revs to about 1850 rpm. A serial number would be needed to get exact numbers. It sounds like the governor control is out of calibration to the low side. You could try adjusting the cables a bit . If you lengthen one you have to shorten the other by the same amount. If it's out a lot you should recalibrate electronically.
Don't mess with the governor control cables. There is an adjustment function in the machine computer. It can be accessed through the monitor panel in the cab. I don't know the codes that give access to it. The head gasket problem does need to be repaired first.
Ok, so I'm getting the correct rpm when manually twisting the throttle, thats good. Does anyone know what the codes are to get into the adjustment function in the computer?
Usually the service mode password is "fff2". You then go to governor calibration. I usually do a calibration and then mess with the cables to get a little more out of it. Yes I do mess with the cables my bad.
Cool, thanks Mobiltech, I'll give it a go when the head gasket is replaced, is there anything I should know about before attempting a governor calibration?
OK so in the process of replacing the head gasket and fixing a couple of exhaust leaks, somehow we have managed to get the engine back to full rpm without doing a governor calibration. Except now it's getting to full rpm at throttle position 9 instead of 10. Is a governor calibration the way to sort this? It's not a major thing having it at 9 but it's bugging me...