Detroit 6-71 Running away

[Ponderosa Pete]

I've got an '85 Ford L9000 with a Detroit 6-71 engine. Engine was running fine and I decided to pressure wash it this past Sunday. Truck sat until yesterday because I was doing some brake work on it. Went to start it yesterday and the engine was full throttle and ran away. I had to put it in gear and let the clutch out to shut it off. Any idea of what could be wrong or is it just a coincidence and an injector is stuck open. Like I said, it ran fine before I pressure washed it. Could it be possible that the pressure washer knocked a wire off? I don't believe the injectors are electrical; am I right? Guess I just should have left the engine filthy dirty. I took the air intake elbow off and covered it with a piece of sheet metal and tried it again with the air throttle down, and it smokes like hell with black smoke. Any and all advice appreciated.

 

[Truck Shop]

First off how many miles and hours are on this 6-71? Best to remove the valve cover and check each injector for free travel on plunger. If not spray it with PB blaster and gently tap back and forth.
Only takes one injector to hang to cause a run away. But depending on hours of use the rack rod and governor could be worn enough to cause it. When started from stone cold does the engine
roll several times before smoothing out? And an injector can hang up at anytime depending on wear.

 

[Steve Frazier]

What would that cold roll indicate Truck Shop? Every 71 series I've driven has had that characteristic, they were all well used construction trucks

 

[Truck Shop]

A few rolls is normal but several usually it needs overheads and buffer screw set.