Kubota L4630 Engine runaway

[lourent]

Good evening all, I need some help please.

I started my engine (V2203) about a year ago, the process was simple. I energized the Stop solenoid by putting the two wires onto positive. Then power the starter and it took. (Engine was already out of the tractor) The motor was subsequently sent in to a engineering shop to rebuild.

Over the last two months I put the tractor together again, new clutch and some mechanical repairs. I did not touch the engine, as the engineer put that together. Today I was ready to start the motor. For the life of me it did not want to take. I disconnected the Stop solenoid, loosened the injector pipe retaining nuts and bled the fuel lines (Running the starter for short bursts). Then tied the nuts up, connected the Stop solenoid and tried again "nothing". Then I disconnected the Stop solenoid again and for some reason turned the key, the engine fired up and ran at idle for about 5 minutes, Then the revs picked up and there was no stopping it.

I blocked the air cleaner with rags after a few minutes the revs came down but the engine did not quit, I closed the fuel at the filter. When the filter ran dry, the motor quit.

Now my questions:
1) How does the fuel shutoff (Stop solenoid) work?
2) In my case the Solenoid was disconnected, why did I get fuel? What do I need to check?
3)The solenoid does work, if there is power to it it retracts the pin (Shaft) on removal of power it extends the pin.
4) The solenoid acts as if it is the wrong way around. (Not possible?)
5) What caused the runaway? (Exhaust fumes re-ingested via the air cleaner?)
6) Can the injector pump cause a runaway? (Timing/Set to rich?)

Also the shutoff lever, when is that shut? I assume when I pull it back towards the back of the tractor, not in its normal position. (It made no difference when the engine was out of control.

Sorry but I'm stumped.
Regards Thys

 

[kubotafreak]

Did they touch the injector pump? The pump is mechanical and will (suck) intake fuel without a lift pump. The fuel rack springs hold the rack in an idle position, the fuel stop solenoid pushes it into the kill position. The rack springs back to this idle spot. My guess is the rack springs are not right. The injection pump rack has little fuel turrets that rotate, changing the fuel volume. That’s what gives you higher rpm, if it has been taken apart they can be put back together clocked 180 out. But since you said it did idle this is prob not the case, because when they are 180 out they start full throttle.

 

[lugbolt]

if u loosened the injector nuts at the pump end to bleed the system, possible that teh delivery valves are now out of place. Could contribute to a runaway. If this is the case the pump will have to be removed and sent out for repair.

You never bleed them at the pipes, always at the bleeder on the pump. of all of the tractors I had to bleed fuel systems on I never once touched the injectors. Never had to. Kubota puts a bleeder on the pump.

runaways can also be caused by a bent rack, which is usually a result of improper removal or improper installation. Or sometimes the rack can get stuck from sitting (rust/corrosion) or if the pump has ever had gas through it the valves can get stuck. Runaways can also happen due to too much oil in the crankcase, where it runs on it's own oil that is vented into the intake manifold. Or fuel in the oil, can cause same thing.

 

[lourent]

Good day gents,

Thanks for the replies, yes the injector pump was removed and rebuilt, as according to the engineer shop it was leaking diesel into the crank case. This is my main concern, that they did not put the pump, High Idling unit and the solenoid back as supposed to. Obviously the rack springs are another concern but at least that I can check.

I read about the fuel turrets in the WSM and doubt that this engineer new about this. We have little to no real Kubota mechanics in South Africa. So even the turrets may be all wrong. For me to fix all of this is a challenge , as it is not something I have ever done before.

The idle may be misleading, as there was no fuel in the system it might not have had that much to start with. When the rev's went, it was near instantaneous and stayed extremely high,

I thought of starting at the Rack springs, are the turrets something I could check? Where to from here, as I really do not trust others to fiddle further with the tractor.( But also not sure if I can trust myself)

P.S. No bleeder on my pump that I can find.

Thanks again and Regards Thys

 

[lourent]

Hi Gents,,

Sorry one more thing. If I remove the injector pumt, then the Timing is gone right? For that I have to open the gear case?

Thanks Thys

 

[kubotafreak]

Hi Gents,,

Sorry one more thing. If I remove the injector pumt, then the Timing is gone right? For that I have to open the gear case?

Thanks Thys

No, you can pull the injection pump out and the timing will stay. The only thing important here, is the shim. It does control the height of the injection pump so do not damage it, as it will be reused.

 

[Russell King]

Hi Gents,,

Sorry one more thing. If I remove the injector pumt, then the Timing is gone right? For that I have to open the gear case?

Thanks Thys

The timing is set by shims between the engine block and the injection pump. Don’t lose any and put them all back. Pretty sure no sealant should be used or it would effect the timing. If there are ZERO shims your timing may be off since I think a shim is always required but more informed people may confirm or deny that.