Hydraulics bogging down machine

[knightgang]

Just received my new to me EX120. While tracking it about 1/3 of a mile to hide it in the woods behind the house, I stopped in the backyard to move something and the machine idled for about 10 minutes. After I got back in, any touch of the hydraulics, whether to track, swing, or move the boom, the hydraulics started bogging down the engine. I looked at the machine twice, both time we allowed the engine and hydraulics to warm up and there was not apparent issues.

Now, the previous owner had what I believe was a pilot system solenoid disconnected and jumped and had a new one on order. I called him this evening and he seemed to think that maybe the jumper came loose and that replacing the solenoid and plugging it back in would correct the issue.

I have been reading here lately and automatically assumed it was an angle sensor issue. I am currently looking through some literature that I received from another member (I have tech manuals for the EX100 and EX200) but would love it if some that has experience with these could tell me what talks to what and if the solenoid that I mentioned feeds a signal to the angle sensor and maybe that is indeed the issue in that that angle sensor is not receiving a signal that will allow it to back off.

It is not fuel related as when it bogs down, it does bellow black smoke.

 

[mikebramel]

The pilot pressure is probably used to unload the pumps so he may well be right

 

[spitzair]

On the top of your hydraulic pump you'll see two sets of wires with plugs going into the solenoids. For troubleshooting purposes you can swap the solenoids, they are identical. If your machine now moves very slow or reacts kinda slugish you know you have a bad solenoid. The pumps move to full stroke on their own if the high pressure side solenoid is busted.

Mikebrambel is absolutely right about pilot pressure being used to contol the pump. How it works to the best of my understanding is that the pumps will move to full stroke on their own but slowly. Pilot pressure is used to control the swashplate angle and thereby pump output almost instantly, and the pilot pressure applied to the swashplate is controlled by the high speed solenoids. In order for the computer to know what the pump is doing it has the angle sensor to tell it what angle the swashplate is at and thereby the displacement of the pump which in turn equals flow volume. Clear as mud right?

 

[knightgang]

Well, I fixed it. The night I received it and it started bogging down, I could swear I saw a lot of black smoke from the exhaust. Although, it was dark and I was trying to view with a flash light.

Here was the issue as it turns out. The previous owner snagged wires from a wiring harness that was hanging down under the tail and broke one wire. We twisted it back together but stated that ever since that happened the key will not shut down the machine. So, he tied a small string to the throttle cable in such a way that he could pull it through the back of the right side cab window and choke down the machine. What I did not realize was that it reached a point that when pulling the rope, it pulled the throttle cable up onto an adacent bracket and was restricting fuel flow. I released the cable and let it run for a minute to regain proper fule flow and everything s,oothed out and it was running exactly as it is supposed to.

I will have to look at the wiring harness and see if I can fix it so that the machine will shut down with the key as it should. Previous owner said that the rod moves to shut down, but it does not push it far enough. I have to take a look and see if it can be adjusted to obtain the correct range of movement so the key shut down will work.

spitsair, you have been all over your 200 with the wiring issues, can you provide any insight on the key shutdown?

Thanks

 

[spitzair]

Well I can sure try at least... This is what I know from my 200-2, the 120 could of course be different... Follow the throttle cable from your injector pump to what looks like a grey heavy duty canvas or plastic bag, inside it you'll find your throttle motor. This motor controls your throttle position as well as shutting it down. There is also a dedicated shutdown motor from what I remember. When I turn the key on my machine to the on position but don't start the engine, I can hear it buzz for a brief moment as it moves the governor to the idle position. Turn the key off and again I can hear it buzz as it moves to the off position. If you can hear it buzz it could be that your cable is out of adjustment, stuck or some other issue. Hope this helps at least a little bit... Pages 156-160 of the EX200-2 Manual I sent you have a pretty good description on how the system works.

 

[knightgang]

Spitz air, that is awesome information. Thanks ..
I'll take a look at that what you suggested and look through the book as well to see if I can get familiar....