The Grand Pooh-Bah
I'm working on a recently acquired 8KW Generac with the 70939 1.0 L diesel Shibaura S753 engine. It has sat for 10+ years in the Mojave Desert. I have changed all the filters and fluids.

When it starts up it goes into high rev and the fault light kills power to the solenoid and fuel pump. The engine continues to run very rough at a slower speed. I have to pinch off the fuel line to stop the engine. ( I didn't know the lever next to the injector was a manual method of sliding the rack)

I pulled the solenoid and the rack is not moving when I try pushing on it thru the hole where the solenoid was. (I tested the solenoid - Good) I pulled the injector pump and the rack slides like butter. The linkage that is attached to the rack moves a little. The spring tension on the linkage isn't very strong though. It doesn't seem to have enough tension to move the rack. The stop lever moves the linkage a little, the governor lever does not move the linkage.

It appears the stop lever does not move the linkage enough to actually move the rack back and forth enough to make a difference. It is moving the rack maybe an 1/8" or less. Something seems to have gone astray with the governor or stop lever or ?

Help!!!!

I can't seem to find a service and repair manual for this engine, only the owners manual.
Generac 8KW Engine # 70939 1.0 L Shibaura S753 Alternator Data: Model 00449-0 SN 3113852 120/240v 1800 RPM
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cookelec
The mechanical governor arm has to move the linkage for the speed to adjust. Is this on an RV??
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The Grand Pooh-Bah
It is a standby generator.
Generac 8KW Engine # 70939 1.0 L Shibaura S753 Alternator Data: Model 00449-0 SN 3113852 120/240v 1800 RPM
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The Grand Pooh-Bah
It now shuts downbut can not get it to stop over revving.  I have adjusted the throttle lever both in and out and it has no effect.  I removed the timing gear cover.  I can't see anything wrong.  Maybe these photos will help explain why the governor isn't working.

[clean1]

[clean2]

[govenor]


Generac 8KW Engine # 70939 1.0 L Shibaura S753 Alternator Data: Model 00449-0 SN 3113852 120/240v 1800 RPM
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The Grand Pooh-Bah
I'm leaning towards injector pump problems.  The reason it was not shutting down even with the fuel pump power removed is one of the three little pins that slide back and forth with the injector pump rack was not engaged.  I corrected that and it runs much smoother. It still over revvs, but now it shuts down when the fault light comes on. 

I was told the pump was rebuilt by a reputable shop but then was installed by someone who might have partially disassembled the pump.  If the pump timing is off would that cause it to over revv?
Generac 8KW Engine # 70939 1.0 L Shibaura S753 Alternator Data: Model 00449-0 SN 3113852 120/240v 1800 RPM
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Peddler
In the second picture the lite flat arm you are holding looks like the tab that is up from the governor treadle appears to be bent though it may be an illusion.  I'm wondering what that tab does and if it could be interfering with the travel of the governor?  I am totally unfamiliar with these engines though and have no idea what I am talking about. 
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The Grand Pooh-Bah
Got the injector pump back, no problems with it.  Going to pull the timing gear cover again. Something with the governor has to be amiss. 
Generac 8KW Engine # 70939 1.0 L Shibaura S753 Alternator Data: Model 00449-0 SN 3113852 120/240v 1800 RPM
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