7274 Run Away Diesel?: Cub Cadet  -- Other Tractor Brands Discussion Forum and Review 7274 Run Away Diesel?: Cub Cadet -- Other Tractor Brands Discussion Forum

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 06-26-2008, 16:22 Post: 154846
joepag08



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 7274 Run Away Diesel?

I bought a used 7274 Cub a few months ago. It has been running OK since I got it. A few weeks ago though I was moving mulch and on a slight down incline when I felt the power disengage (as if I stepped on the clutch) and motor revved a bit. I immediately stepped on the clutch, and throttled down, but the rev continued. I turned the key off immediately and it continued to run but only for about 4-5 seconds. First thing was to check the engine oil and when I pulled the dipstick I got a stream of thin oil out the tube hole. VERY Not good. Because the crankcase was so full, I believe it was the start of a runaway diesel but fortunately it got a gulp of air and killed the engine. Now I need to figure out what's up.

Coolant level was normal. It's possibly diesel fuel getting past the piston rings but that is ALOT of diesel. The previous owner said he had just replaced the clutch. As it is a wet clutch, is it possible he messed something up and hydraulic transmission fluid was getting in?

I pulled the radiator and battery and put a socket on the crankshaft bolt and turned the motor just to be sure it's not siezed. It turned fine so I think I'm OK there. I really thought it was seized since after replacing the fluid to correct level, I could not get it to turn over with the starter. But I think I have other elect problems as the electric has been screwy since I got it.

Taking suggestions on where to go with this. Help would be greatly appreciated.

Joe






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 06-26-2008, 21:04 Post: 154851
PaulChristenson



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 7274 Run Away Diesel?

"fortunately it got a gulp of air and killed the engine."

SORRY that is NOT what happened...The only way to stop a runaway diesel engine is to block off the air intake, either physically using a cover or plug, or alternatively by directing a CO2 fire extinguisher into the air intake to smother the engine.

"was moving mulch and on a slight down incline"

The unwanted oil can also come from failure of the oil seals in a turbocharged diesel engine (turbodiesel), from overfilling the crankcase with oil, or certain other mechanical problems.

"First thing was to check the engine oil and when I pulled the dipstick I got a stream of thin oil out the tube hole. VERY Not good. Because the crankcase was so full"

In many vehicles, a crankcase breather pipe feeds into the air intake to vent the crankcase; on a worn engine, gases can blow past the sides of the pistons and into the crankcase, then carry oil mist from the crankcase into the air intake via the breather. A diesel engine will run on this oil mist, since engine oil has the same energy content as diesel fuel, and so the engine revolutions increase as this extra "fuel" is taken in. As a result of increased revolutions, more oil mist is forced out of the crankcase and into the engine, and a vicious cycle is created. The engine reaches a point where it is generating enough oil mist from its own crankcase oil that shutting off the fuel supply or cutting the ignition will not stop it and it will run faster and faster until it is destroyed.








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 06-28-2008, 20:05 Post: 154923
joepag08



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 7274 Run Away Diesel?

Well you've effectively corrected my hypothesis on the run away. Thank you so much, Paul.

Now do you think you could be just as vehement in telling me something useful?

Another site suggested the injector pump leaked diesel through a failed seal. Any thoughts?






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 06-29-2008, 15:05 Post: 154941
PaulChristenson



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 7274 Run Away Diesel?

Quote:
Originally Posted by joepag08 | view 154923
Well you've effectively corrected my hypothesis on the run away. Thank you so much, Paul. Now do you think you could be just as vehement in telling me something useful? Another site suggested the injector pump leaked diesel through a failed seal. Any thoughts?



Since you didn't respond to the rest of the message...

I'll ask again
What was the oil level after the almost runaway...

LOW? or HIGH?

"First thing was to check the engine oil and when I pulled the dipstick I got a stream of thin oil out the tube hole. VERY Not good. Because the crankcase was so full"
...I don't understand what you are trying to say...

If you are saying the crankcase was overfilled at the beginning and then was LOW...i.e. thin oil out of tube??

Then unwanted oil came from overfilling the crankcase with oil.

If you are saying it was still high then read the following...

In many vehicles, a crankcase breather pipe feeds into the air intake to vent the crankcase; on a worn engine, gases can blow past the sides of the pistons and into the crankcase, then carry oil mist from the crankcase into the air intake via the breather. A diesel engine will run on this oil mist, since engine oil has the same energy content as diesel fuel, and so the engine revolutions increase as this extra "fuel" is taken in. As a result of increased revolutions, more oil mist is forced out of the crankcase and into the engine, and a vicious cycle is created. The engine reaches a point where it is generating enough oil mist from its own crankcase oil that shutting off the fuel supply or cutting the ignition will not stop it and it will run faster and faster until it is destroyed.






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 06-29-2008, 18:51 Post: 154943
joepag08



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 7274 Run Away Diesel?

When I changed the oil last Fall, I added the correct amount. Everything was fine for months. After the shutdown (June), the crankcase was so full that it spewed out the dipstick hole when I pulled the stick. I then drained a large amount from the oil pan. Didn't measure but at least 3 or 4 qts extra. That extra fluid came from somewhere and I'm trying to figure out where. It wasn't coolant. Only other option is diesel or hydraulic.

Someone suggested a diaphram in the injector pump failed and that dumped diesel into the engine. What do you think?

Joe






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 06-29-2008, 22:45 Post: 154945
PaulChristenson



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 7274 Run Away Diesel?

Quote:
Originally Posted by joepag08 | view 154943
When I changed the oil last Fall, I added the correct amount. Everything was fine for months. After the shutdown (June), the crankcase was so full that it spewed out the dipstick hole when I pulled the stick. I then drained a large amount from the oil pan. Didn't measure but at least 3 or 4 qts extra. That extra fluid came from somewhere and I'm trying to figure out where. It wasn't coolant. Only other option is diesel or hydraulic. Someone suggested a diaphram in the injector pump failed and that dumped diesel into the engine. What do you think? Joe



This is a possibility...

There could be a leak anywhere in the injection system...
Here is an example of a leak search on a JD injection system...YMMV...Smile

A. Leakage occurring at any point in the fuel system within the pump compartment should be noticed. There is always some lubricating oil in this area, but it is not difficult to distinguish between lubricating oil and diesel fuel. If fuel is leaking, check for:


1. Loose cap screws attaching pump to bracket or defective pump-to-bracket gasket.


2. Loose cap screws attaching pump bracket to cylinder block.


3. Loose fuel line connections at pumps or delivery valve holder (R930R or R1082R). (Delivery valve holder could be tight and leaking could be due to a leaky delivery valve gasket.)


4. Gasket or gaskets between pump bracket and cylinder not holding. (Also examine surfaces of block and pump bracket.)


B. If the fuel injection pump itself is leaking, due to worn or defective parts, there is a good possibility that the window in the pump body will be filled with a small puddle of fuel. This pocket should otherwise contain only a light film of oil at the bottom.


When examining the pump area, it is well to bear in mind that lubricating oil is metered up to the fuel pump and, therefore, a small amount of oil should be detected coming out of the tappet end of the pump.


If there is no fuel in the bottom of the pump compartment, then the leakage is in the tappet cover area or in the lower portion of the lines between the pumps and injectors. Check for the following:


5. Loose connections between injectors and fuel lines.


6. Worn fuel line (tappet lever rubbing).


7. Loose spray tip retaining nuts.


8. Cracked or burst fuel lines.


It is also possible that fuel is leaking past defective seals in the fuel transfer pump, in which case the fuel will enter the crankcase directly by way of the governor case and will not be found in the pump compartment.






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 07-01-2008, 13:45 Post: 155000
Art White



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 7274 Run Away Diesel?


It's probably diesel fuel or hydraulic fluid! Either would keep the engine running!






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 07-01-2008, 16:40 Post: 155006
kthompson



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 7274 Run Away Diesel?

It seems if it was as much fluid as you say, it would be easy to tell if your hyd fuild was way low and if so it was that, but if it were full or near full it was fuel. At first thought you could tell be the smell but you may not. kt






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Discussion Boards > Active Subjects > Messages as Posted > Cub Cadet Forum

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