More on the Komatsu excavator

So got a chance to look at it today and even got it to start but took 2 people to do so. It is a Komatsu PC200LC. What I did to get it to start was the guy held the ignition in the start position and I jumped the small terminal on the starter mounted solenoid to the big stud that goes to the starter motor. I did try the small terminal to the battery cable one and that did not work but the other way around it did. Makes me think that maybe that solenoid has a battery post and starter post and maybe the 2 are 180 out so if I took the 2 and switched them it might work right. So am I thinking right or is it something else??
By the way measured voltage again today. After charging the batteries. . 12.6 on one and 12.35 on the other and 24.9 on them both.
So what do you guys think do I switch the 2 cables on that solenoid??
Thanks

Almost sounds like you are bypassing the safety switch. imho Jim

I think I'm missing something in what your saying. Here's your post, with my comments on what I'm not understanding.

So got a chance to look at it today and even got it to start but took 2 people to do so. It is a Komatsu PC200LC. What I did to get it to start was the guy held the ignition in the start position and I jumped the small terminal on the starter mounted solenoid to the big stud that goes to the starter motor. ***********There may be two small terminals on the solenoid. One gets power from the key switch, and is used to power the solenoid to make it engage. The other, if it has another, is powered up through the solenoid when it pulls in, just as the starter motor does. The two big posts are usually more or less interchangeable. In other words, it doesn't really matter which is connected to the battery, and which is connected to the starter motor. You should be able to jump from the big battery post on the solenoid to the small S post on the solenoid to make the starter work.************************

I did try the small terminal to the battery cable one and that did not work but the other way around it did. *********This is where I am really confused. Are you saying you did what I just mentioned above and it didn't work?*********

Makes me think that maybe that solenoid has a battery post and starter post and maybe the 2 are 180 out so if I took the 2 and switched them it might work right. ***************** Again, I'm still confused here, but if there are two small terminals on the solenoid and one isn't working to start, but the other is, then it sounds like the two posts were probably different on that solenoid than on the original. I've run into this quite a few times, and it can often be a PITA when the wires are routed one way, and the terminals wound up another. If your terminals were changed, and who ever took the starter off didn't notice the difference when putting it back on, then that could be a problem. The only thing is it would not work at all with the two swapped, so it it had been working and quit, then this wouldn't be an issue. *******************

So am I thinking right or is it something else??
By the way measured voltage again today. After charging the batteries. . 12.6 on one and 12.35 on the other and 24.9 on them both. So what do you guys think do I switch the 2 cables on that solenoid??
Thanks

*********************************Post back when you get a chance. If you've got any way to post some pics of exactly what your dealing with, it would make knowing what was going on a bit easier*****************************

You know, I hadn't thought about that. His explanation of how they started it has me a bit confused, but you are right, that way bypasses the safety switch, and I hadn't even thought about it......

The safety switch is inside the left arm wrest, and is actuated by the lever that turns the hydraulics on and off. If that switch goes bad, the machine will not start. If it is suspect, it can be bypassed in order to check it.

The solenoid on the starter has 2 big posts and one small post. The wire from the small post goes to what looks like maybe another sort of solenoid/relay. I did try going big post to big post but that would only spin the starter and not engage the flywheel. I did the battery post to the small post and that did nothing at all. Bit when I did the small post to the starter post with the ignition switch held in the start position it turned over and started up

Well if the guy tried to start it with the normal ignition start set up the solenoid on the starter chatters and the engine turns over but slow and as if the solenoid is making contact and then not very fast.
When I went form the small terminal on the solenoid the the starter side big post it spun over and fired up. That small terminal has a wire that goes to some sort of other thing that maybe a solenoid/relay but not sure what it is or what it does but it has a number of wires on it

So why switch the wires has someone else been playing with the system thats the fun of trouble shooting you never know who else before yu just mite have been playing around as those wires didnt change them selves.

After reading all from you both it sounds like when trying to start it with the key it chatters and turns over slow, only getting 12 volts? I don't quite understand what he jump to get it started though. Jim

Did you measure voltage at the small terminal of the relay solenoid when your helper tried the start button? I would measure voltages before switching wires around:if you are not getting voltage then you have a problem such as neutral/safety switch.I would believe the starter button sends voltage thru some sort of safety switch to the relay which, when energized, sends voltage to the starter solenoid small terminal.I would like to see a pic of what you are working with-I worked on truck starting problems for 40 years,and saw a lot of different problems.Mark

Measure the voltage on the small starter terminal with the switch NOT held in start position. If you have voltage there, the solenoid winding is powered internally. When the small terminal is grounded, the solenoid is actuated.

When you shorted it to the starter lug, it provided a ground. Once the starter was engaged it actuated a hold in circuit, like on a Delco starter.

I agree, somewhere there is a safety switch not making, a relay not connecting, a broken wire, high resistance in a connection.

That's my theory anyway...

A picture would be sort of hard to do since just to get to this starter I had to lay on my belly and it was all I could do to reach it when I had to install the starter this past summer. This machine is by far the biggest machine I have messed with and also way to new and has to many dummy switches on it

Starter was rebuilt this summer and the solenoid replaced by a re-builder in the area and I then installed the starter/solenoid. It has pretty much done this since I installed it this summer but would start up till not long ago so that is why I am thinking the battery and starter big cables maybe 180 out.

The big thing that is odd is the fact it will try to turn over but the chattering of the solenoid does not let it spin up fast enough to start the machine. When I jumped the small stud on the solenoid and the big stud going to the starter it spun up and started which has me thinking there is a battery and starter side to that solenoid. Would be nice to have a wiring diagram to it but I don't have that so sort of going at it blind

The way this machine is it can not get only 12 volts since the batteries are hooked up in series.
This solenoid is a lot like an old Chev solenoid that had 2 big posts and one small post. When voltage is hooked to the small post it should pull the solenoid in and that in turn causes the starter to spin up.
But in this case it sort of spins up but the solenoid seems to make and break so the starter never gets up to full speed so in turn the engine does not start up.
Then when I jumped the small terminal to the starter motor side it started up when he held the ignition switch in the start position.

Old, is that thing a real old one, like a dash 3,5,or newer like a 6, or a real new one like a dash 7,8? Just by guessing from what you say, I'm thinking it may be a dash 3 or 5. Both are blue and yellow, on a dash 5 the side panels are flat, on a dash 3 there is a step on the side panels along the side where the blue and yellow meet. A dash 6 is more rounded at the counterweight and is yellow and grey. I believe the starting system on the dash 3,5,6 is all pretty close. Maybe NCWayne will know better on this, but I was thinking that the engine would still start with the safety lever up, that it just disabled the hydraulics? NCWayne probably DOES know better than me since I believe the dash 3,5 Komatsus were probably done being built before I was born lol. I did a rewire on a PC300-3 for a guy this summer, it has a wiring fire. The swing brake controller had shorted to ground and vaporized a lot of the harness, including the starting and alter alternator portion. After rewiring the melted wires and replacing the swing brake controller ($350), I now had a "no start" condition. I checked the alternator "R" terminal not running and had voltage. Needs an alternator. Replaced alternator. Tried again, no start, found that the battery powered battery disconnect was losing hold, burned up, and so was the starter solenoid. I replaced both of them and then we were cooking with gas. I am guessing the internals of the alternator, the starter solenoid, and the disconnect were ruined when the wiring shorted and all melted. After all of that, the only thing that didn't get ruined was the small relay or solenoid above the starter, I believe it is called a "safety start relay" but I can't remember for sure. If it is a dash 7, or 8, all I can say is "have a good time with that" lol.

Ross

(quoted from post at 18:50:14 10/18/15) Starter was rebuilt this summer and the solenoid replaced by a re-builder in the area and I then installed the starter/solenoid. It has pretty much done this since I installed it this summer but would start up till not long ago so that is why I am thinking the battery and starter big cables maybe 180 out.

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Why do you think that the cables some how jumped off the terminals and some how jumped back on 180* out and I assume the nuts are tight on the studs.

As said it is a PC200LC Mostly yellow in color. I did check voltage on the R terminal of the alternator and even removed it to see if it would start with it removed but that did nothing. Had something like 2 0r so volts on it when hooked up which could have been digital meter reading false voltage.

The starter was rebuilt this past summer so the starter one could have been put back on wrong by the person who rebuilt it. When I installed it I hooked the battery cable up to the only big post that did not have a wire on it and that is why I am thinking there maybe a true battery post and a true starter post and if so could be 180 out.
Solenoid looks like an old Chev 3 wire type and on them the lower post of the solenoid went to the starter and the upper to the battery and on this one they are backward os what is on the old Chev ones

Ok, having read everything now, lets start over.

The small solenoid (safety solenoid) is there so the higher amperage required by the actual starter solenoid doesn't have to pass through any switches, or electronic components. SO, first thing to do is check that solenoid. First insure you have 24 volts going to one of the big posts on it. Next, insure you have voltage going to it, from the key switch/start circuit. If no voltage here, suspect the safety switch in the left arm rest. Now insure you have 24 volts on the second large post when the solenoid is energized. This should be providing power to the small post on the solenoid attached to the starter. You can easily bypass this solenoid with a piece of heavy (say 10 or 12 gage) wire. Check it by running your wire from the big, hot post to the small post, and see what happens. Too, you can jumper the two big posts and see what happens. Either way, with it jumped, the starter solenoid should be powered and engage.

One thing, when doing any of these tests, the key switch has to be ON. If it's off, the master switch won't be making the system ground, and you won't read voltage anywhere.

On that note, the master switch could possibly be going bad. When it pulls in and makes the ground, it's doing so good enough for the small solenoids to pull in. When the starter begins to pull a higher amp draw, the connection breaks down. The connection breaks, the solenoids lose power, and the starter stops...........and the cycle repeats as long as they key switch is held in the start position. This would account for the chattering your seeing. You can also bypass the master switch by jumping the batteries ground straight to the frame.


Too, you can unhook the battery wire to the starter solenoid and check everything with it unhooked. If everything works like this, but not with the starter actually working, I would suspect the master switch problem I just described.

I got a bit off track there, but with the small solenoid checked, go to the solenoid on the starter itself. Once again, insure you have 24 volts, from the battery, to the big post on the solenoid. If the small solenoid is working, the small post on the starter solenoid should read 24 volts when the key switch is actuated. This should cause the starter to pull in.

This pretty much covers everything I can think of on any Komatsu starter circuit I can remember working on. Beyond the idiot switches, like the one on the safety switch, and the whole deal with the alternator telling the computer the machine the engine is running so it can't start, the circuit is actually pretty simple. Check out the things I mentioned above, and get back with us. I'll pick my brain some more if necessary, but given the info so far, this is all I can think of.

OLD:

Try this - it's a full shop manual in downloadable PDF.

http://catexcavatorservicerepairmanual.com/komatsu-service-pc200-5-pc200-5-mighty-pc200lc-5-pc200lc-5-mighty-pc220-5-pc220lc-5-shop-manual-excavator-repair-book/


Hope this helps.

Doc

Rich I have two 220s whenever ours did that it was the alternator bad. I can't explain it but I remember cranking at the starter and running until the batteries went dead and having alt fixed. Good luck.
Ron

Not sure of what your saying or if we are on the same page. What I think is the small solenoid has not big posts on it just say 5 or so wires and one goes the the one small post on the solenoid. So not sure if that is what your talking about or not. I do know where the master switch your talking about is and have though about trying to jumper it and see what happens but not sure that can be done safely.

So just for grins will it hurt any thing if I switch the 2 heavy wires on the starter solenoid?? Figure that would be the easiest way to at least know that it works or does not matter which is where

(quoted from post at 11:47:44 10/19/15) Not sure of what your saying or if we are on the same page. What I think is the small solenoid has not big posts on it just say 5 or so wires and one goes the the one small post on the solenoid. .

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What you're referring to with 5 or so wires sounds as if it a starter relay. If so it may be your non starter engagement problem. Does starter have a post on the side of case(outlined in blue) similar to a JD 24 v system or just one large post that solenoid on starter is attached to. Do you know if starter,gen & regulator are grounded to or isolated from frame?

Starter has a wire that is heavy coming out of it that hook to the solenoid. It is a lot like the old Chev 3 wire 2 big cables and then the small solenoid pull in wire.

(quoted from post at 19:06:41 10/18/15) Old, is that thing a real old one, like a dash 3,5,or newer like a 6, or a real new one like a dash 7,8? Just by guessing from what you say, I'm thinking it may be a dash 3 or 5. Both are blue and yellow, on a dash 5 the side panels are flat, on a dash 3 there is a step on the side panels along the side where the blue and yellow meet. A dash 6 is more rounded at the counterweight and is yellow and grey. I believe the starting system on the dash 3,5,6 is all pretty close. Maybe NCWayne will know better on this, but I was thinking that the engine would still start with the safety lever up, that it just disabled the hydraulics? NCWayne probably DOES know better than me since I believe the dash 3,5 Komatsus were probably done being built before I was born lol. I did a rewire on a PC300-3 for a guy this summer, it has a wiring fire. The swing brake controller had shorted to ground and vaporized a lot of the harness, including the starting and alter alternator portion. After rewiring the melted wires and replacing the swing brake controller ($350), I now had a "no start" condition. I checked the alternator "R" terminal not running and had voltage. Needs an alternator. Replaced alternator. Tried again, no start, found that the battery powered battery disconnect was losing hold, burned up, and so was the starter solenoid. I replaced both of them and then we were cooking with gas. I am guessing the internals of the alternator, the starter solenoid, and the disconnect were ruined when the wiring shorted and all melted. After all of that, the only thing that didn't get ruined was the small relay or solenoid above the starter, I believe it is called a "safety start relay" but I can't remember for sure. If it is a dash 7, or 8, all I can say is "have a good time with that" lol.

Ross

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from what people say about repairing equipment that has had a fire you should probably get paid about $20,000 for that job. Hope you did!

No fire on this machine but it is one that has been run hard and put away wet so to speak.

Unfortunately I haven't seen one with that many wires, so I'm lost now myself. Do me a favor. The side of the machine it may just say PC200, but the serial number plate ought to say something like PC200- ? This is what I really need to know to be able to get more info on it, as they made changes between say the -3's and the -6's.

With that I ought to be able to come up with something better on the system than troubleshooting by guesstimation.

So just to make it easy where is the serial number plate at. I have not noticed it any place but then again I only have the fun of fixing things for him so I do not always look at them real close for serial number etc.
It will be Wednesday or Thursday before I get back to it so. When I do get back to it I have planed to switch the 2 big cables on the solenoid just to see if that does any thing or not

On most excavators it will be on the lower, right, corner of the cab, right under the boom. Sometimes they will be stamped on the center of the main frame, again under the boom, and between the bases of the boom lift cylinders. These are two places I've seen them put. If not in one of these places, all I can suggest is to do a search, because the serial number will usually be needed for any parts he may need in the future, so it would be a good thing to have on hand regardless.