Kobota engine stop solonoid

[jemjack]

I have a 3 cylinder Kobota diesel engine fitted to my excavator , but the engine will not start after not being used for 3 weeks. I have taken the stop solenoid out and it withdraws correctly when the starter is turned on but when I look inside where it is fitted, the piece in there which should follow the solenoid pin does not move out, does this make sense? So I would like to take the front plate off to see what is the problem, the front plate has the accelerator lever and stop lever mounted on it. Or I could take the top plate off which has the 3 fuel lines attached, I would think that this is the fuel injector pump, so I would certainly like to know what is under it before working on it!! Does anyone have a manual for this part of the engine, or can tell me why this is sticking please. The engine appears to be the same as the b1600 tractor engine, except that it has a solenoid stop where as the tractor only has a manual stop pull button.

best wishes Jemjack

 

[EE_Bota]

I have no real information on that engine. I just wanted to offer something for consideration. I am not there to see the engine, but if I were, I would look carefully to see if the fuel stop solenoid is supposed to move anything at all EXCEPT when it is trying to turn the engine off. I would think that when it is NOT trying to turn the engine off, it's mode of operation is to simply stay out of the way to allow the rack to move freely under the control of other mechanisms.

Hopefully others who know much more will chime in with specifics.

 

[gwdixon]

I have no real information on that engine. I just wanted to offer something for consideration. I am not there to see the engine, but if I were, I would look carefully to see if the fuel stop solenoid is supposed to move anything at all EXCEPT when it is trying to turn the engine off. I would think that when it is NOT trying to turn the engine off, it's mode of operation is to simply stay out of the way to allow the rack to move freely under the control of other mechanisms.

Hopefully others who know much more will chime in with specifics.

Yup, that is how it works on the tractors. It is benign until the engine is shut off, then a relay applies voltage to the solenoid for about 10 seconds cutting the fuel to make sure the fuel supply is run dry, and then it returns the shut off rod to rest with an audible click.

Removing the solenoid or disconnecting the rod should allow the engine to keep running.

The excavator must be different since the OP states that the solenoid rod is withdrawn when the switch is turned ON. That ON action must open the fuel line. If it is working properly then something else must be causing the non-starting problem. Either that or the solenoid is working opposite of what it should.

 

[jemjack]

Hi Thank you for your replies, the solenoid definatly withdraws when the ignition switch is turned on and is held against a spring for as long as the engine is running. so there must be a bar which should spring out when the engine is running. and this appears to be sticking, if i poke a screwdriver in to the bar I can push it a few thou's but it will not move out a cm as i think that it should, The solenoid retracts a cm. I would like to remove one of the plates covering it if anyone has any ideas or a manual for this bit? please.

 

[radioman]

If solenoid is moving in when key is turned on to get ready to start, then you got a short somewhere. check the solenoid wiring.

 

[EE_Bota]

I researched this the other day for a fellow TBN poster. My manual covers a BX1800 and a BX2200. My tractor (the BX2200) is supposed to be pulled back when the starter is firing, but when to key is released, a separate circuit holds it back.

On the BX1800, there is a time relay that operates the stop solenoid for ten seconds after the key is turned off, they assume 10 seconds of operation will stop the tractor, then it stops sending current to the stop solenoid after that to keep from killing the battery.

In summary: Some take continuous power to allow the tractor to keep running. Others require power only to turn the tractor off. The two engines listed in my manual are the D905-E-BX (my BX2200) and the D722-E-BX for the BX1800. Noteworthy is that the 722 has an additional fuse, and the time relay that handles the stop solenoid.

I hope this helps clarify some issues. I am going back into the manual, so I may find something else to post. I will look, but I would be very surprised if there is detail on the actual injector pump, since this is usually considered outside of what most folks can work on.

 

[EE_Bota]

I looked in the manual, and it gives a theory of operation. You might do better searching your exact pump online for information. This one is a Bosch MD series in my tractor.

In my manual, there is not enough detail to suggest taking anything apart. There is more detail on the actual injector.

The manual is dealing with two engines and you never know when they forget to deal with one of them during a procedure write-up. But there are tests like injection timing, etc that they tell you how to do. During the tests, there is a step where you remove the fuel stop solenoid, and turn the flywheel to test pressures, etc. The salient point being that when the solenoid is removed, it should pump. The diagrams are very small, but it looks like the fuel stop pushes a rack that turns a plunger into a positon to which the fuel being pumped is bled internally so the engine can not run. When the stop solenoid is out of the way, the rack that was actuated by the stop solenoid is now able to be moved by the governor system output linkage.

If your governor system is frozen, the rack will not move. However, you should only be able to move the rack with the actual governor itself. Since your engine is not running, the springs should be winning, and the rack should move at least enough to close the bleed hole in the pump plunger system so your engine can start. Moving your throttle lever may be necessary to open the rack to it's fullest extend, but I have seen governors spring-ed various ways. If you move the governor output linkage and or the injector pump throttle linkage, you should be moving that rack directly.

 

[eepete]

The solenoid on my B21 (called the "stop solenoid") works like this:

It has two windings, one is about .4 ohms, the other about 12 or so. When you crank, both windings are energized. The low ohm coil pulls in the solenoid. The higher ohm one is holds it in. When energized/pulled in, a sliding bar allows fuel to flow. When it's off (when you turn the tractor off) the holding coil is turned off, the solenoid rod pops out, the bar that switches the fuel moves, the fuel is cut off, and the engine stops.

The thread on this repair is titled "B21 starts, then stops immediately on key release" in case anyone wants to search on it.

So my money is on the mechanical sliding bar. Agree with all that there are stop and start flavors of these solenoids. Only new info I think I'm adding to this thread is the two coils, a pull-in that follows (and comes from) the starter solenoid, and a holding coil that is on if the tractor key is in the on position.

Pete

 

[EE_Bota]

Thanks EE_PETE. I am just reading the manual, but it sounds like you have real life experience, which is better always.

It does bring up a good point I should have mentioned. The Solenoid on one type has a three wire connection, but the other type has less than three. That is one good way to distinguish types.

 

[jemjack]

Hi everyone, thank you very much for all your help. EE Bota And EE Pete you have hit the nail on the head, the solenoid is 3 wire, and not the problem, as it is working fine, the problem is that the "rack" "slider" call it what you will does not move out when the solenoid withdrawers, If the solenoid is removed,the rack should move out, thus alowing the fuel to the injectors, and the engine to start.Everything inside is nice and oily, no rust at all. I can see no reason why the rack wont move out, it did when I last used the digger 3 weeks ago,In so much as the engine ran perfectly but in the past when i have shut the engine off it has continued running for a few seconds more before stopping. I dont know whether this has any bearing on the problem? I have tried moving the throttle and stop lever back and forth but this has made no differance. The engine by the way is a Kubota 3 cyl diesel D1005-E if this is any help, Has anyone got a parts list of this or similar engine please.

thanks again for all your help
Jemjack