Originally Posted by kilmaine
I have a theory. I couldnít understand why it would stick at a large throttle opening when the previous run up 3 years ago was at modest revs. Then I wondered if when the shut of solenoid is operated and presumably the fuel supply is cut does the governor attempt to open the throttle in order to maintain revs? If so the fuel rack might well have then stuck in that position.
On your injector pump
the high pressure fuel is delivered to the injectors by individual elements in the injector pump
which are constant stroke and variable volume,controlled very precisely by the rotation of the plunger helix through about 180įby the fuel rack which is in turn controlled by the governor via a linkage and spring.
For the sake of discussion we can make 5į the low idle point and say 170į the governed maximum rpm full load setting.... the other 10į is the cold start overfuel position and is controlled only by the pull cable thatís hanging at the rear of the injector pump ( the knob is marked coldstart)
And hereís the point........if just one of those plungers gums up and seizes, it locks the rotation of the other 3 and the governor ( and often the stop control too) canít push the rack to a low or no fuel position and you have a 3 cylinder ungoverned runaway, occasionally with catastrophic damage to the engine.
If this is what caused your un commanded overspeed you were very lucky that the stop solenoid was able to rotate the stuck plunger and shut er down.
Before you try another start, remove the air filter from the intake and be ready with a book or a bit of plywood
to block off the air supply.
Interestingly only some racks get stuck in the full fuel position, many that Iíve seen and worked on stick in the no fuel.... no start position.