We have a 98' 312BL, 8JR I think- that will not auto idle down when the machine is enabled. As soon as you disengage the lever on the right to disable the hydraulics it idles down as it should. The top throttle cable had some slack in it so I tightened it up, that really didn't do anything. All the positions work on the dial for the throttle as they should. I think it might be a electrical issue, bad switch somewhere... any thoughts?
Try cleaning the starter debris off the end of he speed sensor screwed into the backside of the bell housing for a start it might sort it out
Sounds like a pressure switch is stuck so that the computer thinks the hydraulics is used all the time and won't let the engine idle down. There's a few scattered around the machine but if you measure the following wires at the controller connector A, L970 grey pin6 Auxilliary A771 Purple pin7 Implement L971 green pin18 Travel None shuld be grounded when machine just idling and not operated,
Where would controller connector A be located?
The controller is mounted under the seat in the cab.
Hi Guys, I got some more info. I did clean the speed sensor which didn't make any difference. I didn't get a chance to check any of the controllers like Per suggested but I did get and preformed the procedure to check the codes and calibrate the governor. The governor went right through the calibration without a problem the first time. The codes I got out of error log were 2303- governor actuator dose not move, 420c- electric power supply is too low (below 23 volts) and 4301- data mismatch 1 between alternator and speed sensor (alternator is abnormal). There we no real time codes and the real time error code (attachments) were 4208- spare PWM sensor 1 is open in circuit and 4209- spare PWM sensor 2 is open in circuit. Can anyone make some sense of this information?
Nothing relevant, go ahead and check the status of the pressure switches.
Will it idle down if push button on top of right controler ?
Yes- but only when the safety lever is down (disabled hydraulics). When you raise the safety lever to enable the hydraulics the rpm's go to the setting on the dial which matches the number on the screen and it will not auto idle until you put the safety lever down again (disabled hydraulics).
I'm not sure where they all are. I did check everything on the main valve bank, I think there were 3 there. I unplugged them, none of the sensors had continuity (the machine was running- I didn't check when it was not running) and all were supplied with about 16 volts- didn't matter if the hydraulics we enabled or disabled. I'm not sure what I should of gotten for a result. I will also try the connector A wires.
Today I rechecked the sensors while the engine was running and found one that had continuity. I think it's the sensor for the joy stick controls. It's located closest to the cab as you climb up on the machine. When you unplug it you cannot rotate the machine, it must send a signal to unlock the swing lock. I did plug it into the other sensor wire and the travel alarm came on. I also did swap the the sensors with one another to see if that would make a difference, it did not. It seams that joy stick circuit is flowing enough oil to trip the sensor and keep the machine from idling down? When you enable the hydraulic system the engine revs drop a little, just enough to notice. Per- I couldn't find any wires under the seat, only wires going into the ecm we the closet to the seat at all.
That switch senses pilot oil pressure fed to it through an orifice and that pressure is drained via the control spools when they are in their center position. A small hose connected to the pilot block drains that oil from the main valve, it might be a kink in that hose preventing the draining. It connects on the end of the main valve towards the tank and should be marked DL6 then it goes to the pilot block in the pump compartment, marked DR3 on that.
There should be three pressure switches on the machine. All are in the pilot circuit, one in swing, one in travel and one for implement. When any function is actuated the switch closes and increases engine speed, now you can also shut that system off (AEC) with a push button on the monitor or in the right hand console (can't remember witch). If one of the three switches is bad the AEC (automatic engine control) will not work. It should probably idle down with the joystick button and then immediately increase back to the dial setting I would think. Hope this helps
I checked everything and no kink. I found a R3 hose but nothing numbered higher than 4...? It also seems the machine doesn't like to turn very well in either direction, but dose track well straight and seams pretty powerful. Not sure if it's related or not but thought I'd mention it. I do have a service manual on it's way so I can follow the hydraulic function. I wonder if it's a internal hydraulic problem, possible plugged return filter or ???
The travel issue sounds like oil leaking pass the gland seal in the swivel. A quick check would be to cap off the lines going to one motor and put the lines from the other motor in a bucket. Run the lever for the motor thats blocked off in both directions and see if you get oil from the open lines in the bucket. Be careful you could make a mess
Don't know if you checked this BUT ? ...... check to see if the cables off of the idle/speed control motor (located behind right rear door ... up on top) if they are not seizing up especially when the machine get up to operating temp, not just the engine but the whole machine, like when parts of the machines steel is so hot you don't want to lean on it ..... I had the simular issues ... the cables outer shell were actually melted due to the heat off of the muffler behind the heat sheild (behind where the control motor is located) the muffler has a plug on the bottom of it to apparently drain off soot or some stupid thing, and the plug was missing for years (probably before I got the machine) exposing/blowing sooty direct heat into the compartment When those cables are seized they can cause the electric speed motor to stall and burn out as mine did ... it started out as an intermittent thing and progressively got worse till it finnally wouldn't do a thing and had to bungey the throttle linkage wide open but still letting the govenor do its thing .... was pretty testy especially to start up a cold engine and have it go to wide open throttle ..... but what do you do .... that assembly, motor and cables complete is not cheap, and you can not buy those parts individually ....... just thought i'd give another angle to what might be going on with yours what mine did a few yrs ago ...... keep us posted .....GK
Hi Craft, Mine will idle down anytime the lever is not engaged to enable the hydraulics. I have been working it in the heat the last few days and as soon as you disable the hydraulics it will idle right down. It's not a major problem but I want it solved before it turns into something worse. Hopefully my service manual will arrive soon so I can get into it. I really appreciate all the suggestions and welcome any more, we'll get it figured out! Thanks.
Update on travel issue... My cousin was running the machine yesterday and he said it acted like it was traveling and trying to turn in high speed. He said compared to his Komatsu PC 120, the 312 acts like it's in stuck in high speed. The travel speed dose not seem to differ at all when switching on the control panel between high and low speed.:beatsme Dose anyone who knows about the hydraulics on the machine think this could be related to the idle problem? Something is happening that is activating the pressure sensor in the implement circuit and I think that is keeping the AEC from working.
Did the machine idle down when you unplugged the sensor that had continuity?
No it did not, and the swing lock remained locked with it unplugged also.
Any more news on your problem masterwelder?
Problem solved... Funny you should ask Jam, I just got home from finally figuring out and fixing what the problem was. As it turns out it was the pedal that would run a thumb or hammer. It had one of the spools stuck partially open letting flow go right to deadhead . I don't have any attachments in use right now, and the last attachment was a hammer. It was a pain in the a** to free it up:Banghead, but we got it and pinned it so it won't move. Once it was fixed everything is back to working like normal . Thanks to everyone for there suggestions and advise.