3800 tractor

[trapper100]

engine suddenly reved up out of control knocked and smoked . did this twice

 

[North Idaho Wolfman]

You have a problem!

Or should I say you have a problem with the injection pump!

 

[pejepscot]

Trapper, is it cold where you are? Did this happen upon startup or during operation?

 

[Daren Todd]

I've had a diesel run away before. Would have bet my right testicle that the injection pump was out. Installed a new injection pump. Had the same issue with the engine running away. Turned out to be an o'ring in the top of the fuel filter base. In this case the fuel pump was before the fuel filter so it wouldn't lose prime. And for some reason it wasn't leaking fuel like you would generally think it would. It was mixing just a tiny bit of air into the fuel, causing it to run lean.

Some diesels will act like the engine is running away, just before they run out of fuel. Has something to do with fuel/air ratio. Not sure of the science behind it, but I've seen it happen. So make sure and rule out a fuel system issue before spending the money on the injection pump.

That being said, most of the time it is an injection pump issue when the motor runs away like you stated

 

[sheepfarmer]

For future (hopefully never) reference, what do you do if your tractor does this?

 

[coachgeo]

For future (hopefully never) reference, what do you do if your tractor does this?

Block the air intake so there is no Oxygen to burn. Watch your hand! Best is a piece of flat something, 2x4? but even good size rag will do.

I've strongly considered an old style RV sewer valve on the air intake of both my tractor and my Tribota (Kubota powered Triumph Tiger) just for this purpose.

 

[Daren Todd]

For future (hopefully never) reference, what do you do if your tractor does this?

Familiarize yourself with the manual shutdowns on your tractor. I haven't had it occur on a kubota, so I'm not sure if the manual fuel shutdown lever would work or not. On the older ones, the compression release will work. The big thing is to either take away the fuel or air. Or stall it out if you happen to be in hi range. I've had customers throw a rain coat over the air breather, and others cut the fuel line. Both achieved the same results which was to get the engine to shut off. Crimping the fuel line with a pair of pliers will work also.

Of course if it does happen, it will usually scare the hell out of you and panic mode tends to set in especially the first time it happens to you

 

[CaveCreekRay]

Not sure if some of those ideas would be safe on a moving machine...

Howsabout turning off the start switch and letting the fuel shutoff valve close?

No gas=no go.

Works every time we shut our tractors down. (Same thing they teach in Drivers Ed.)

Anyone who grew up playing with model airplane engines knows what mixture does to a motor. Too rich and it smokes and sputters. Lean it out and it runs better. Peak lean and it absolutely wails but, in short order, it overheats and melts. A sure sign your model was about to run out of gas was the 5 second wail of power right before the engine quit.

Same for gas or diesel engines. They have to run under peak lean to keep the combustion temperatures low enough to prevent overheating. Gas engines will "pre-detonate" (aka knock or diesel) if run too lean, as the engines with early environmental systems in the 70's did. Some car motors would get so hot they'd diesel after shutdown with tiny red-hot bits of carbon acting like glow plugs.

My wife has a little DR-200 Suzuki which ran incredibly lean for emissions testing. The engine was so lean, the chrome exhaust pipe blued from extremely high exhaust temperatures. After a few miles in the summer heat, the case would get so hot that shifting became harder as the internal parts would bind. They cancelled emission testing for motorcycles in Phoenix last year and I opened up the mixture 1 and 1/2 turns. Runs WAY cooler now and it starts so much better.

 

[Daren Todd]

Ray, usually with a run away situation on a diesel, something has let loose in the fuel rack where the rack is disconnected from any fuel controls internally in the injection pump. The engine literally jumps to wide open throttle. We're talking max rpms for the engine (5000 plus rpms ), not where the pins set for max rpm for the foot throttle or hand hand throttle. (3200 rpms)

If it has an electric fuel pump, then yes, shutting they key off will shut the engine down. If you have a mechanical fuel pump or is gravity fed, then you need to cut fuel or air flow to get the engine to shut down.

If it's running away and your moving then the best thing to do, is to stop moving first. Then deal with the racing engine. Wether it's letting off the hydro pedel, or pushing in the clutch, putting the transmission in nuetral and locking the brake.

 

[sheepfarmer]

Thanks guys, sounds like on my HST I should put it in neutral,set brake, turn off key, jump off and turn fuel off with lever above water separator? The latter lever is easy to get to if one is panicky...

 

[Daren Todd]

Keep in mind that it's fairly rare for it to occur. I've only encountered it three times in ten years. All three were green motors with mechanical fuel pumps. First two times turning the key off didn't shut down the motor and it was an internal failure in the injection pump. Third time it happened, the key would shut down the motor. In that case it was a pin hole air leak in the filter base between the fuel pump and the injection pump. But didn't realize it had an issue with the fuel system till after I replaced the injection pump.

If you run into that situation where it runs away and will shut down with the key, then you need to bypass the filter base and use a known clean source of fuel and test the fuel system first before diving into the injection pump fuel lines cheap!!!!

 

[CaveCreekRay]

My old F-1700 was 30+ years old when I got it. The throttle lever was able to shut off the fuel supply if you went that last 1/8 inch. Having that ability would be handy for a mechanical fuel control gone goofy.

Sure was fun getting the tractor to idle incredibly slow...

"pahhh-tookahhh pahhh-tookahh..pahh-tookahhh..."