JD 2240 Runaway engine, resulted from return fuel hose getting disconnected

[fritza2tt]

fritza2tt

In my first encounter, when the engine began to knock I reduced power and stepped on the clutch to unload the engine. And that was when the engine "ran away". I later discovered that the fuel return line connection at the tank filler neck had separated.[/quote}

So If I'm understanding you correctly you reconnected the return line hose at the tank but didn't remove the diesel soaked air cleaner elements and engine immediately ran fine?????????

If your tractor(one out of 1000's of JD utility models built) did as you state I think that would not constitute a "design flaw"[/QUOTE]

Tx Jim, there was no Diesel-soaked air cleaner present. Try to visualise this: you are in the field bush-hogging. The engine is running between 1,500 and 2,000 RPM. Suddenly the fuel return line slips off and fuel ''dribbles' down behind the tank in front of the radiator cooling fan. The fuel is sprayed and sucked in by the fan, mixes with the air and forms a combustible fuel air mixture. This fuel/air mixture is ready to burn if a spark would set it off. But instead some of it is sucked into the air cleaner. (If a spark was generated there, the air cleaner would explode.) From the air cleaner the ready to burn fuel/air mixture continues into the engine where the heat of compression becomes the trigger it and makes it detonate!. There is no progressive burning here, the entire charge detonates simultaneously at once and you hear it as a ping or knock.

 

[RickB]

Tx Jim, there was no Diesel-soaked air cleaner present. Try to visualise this: you are in the field bush-hogging. The engine is running between 1,500 and 2,000 RPM. Suddenly the fuel return line slips off and fuel ''dribbles' down behind the tank in front of the radiator cooling fan. The fuel is sprayed and sucked in by the fan, mixes with the air and forms a combustible fuel air mixture. This fuel/air mixture is ready to burn if a spark would set it off. But instead some of it is sucked into the air cleaner. (If a spark was generated there, the air cleaner would explode.) From the air cleaner the ready to burn fuel/air mixture continues into the engine where the heat of compression becomes the trigger it and makes it detonate!. There is no progressive burning here, the entire charge detonates simultaneously at once and you hear it as a ping or knock.

As you describe, it is impossible for leaking fuel to get into the engine without passing through the air filter. And if fuel was pulled through the radiator core by the cooling fan, it could not possibly enter the engine with the intake air because the air intake is ahead of the radiator and fan. None of this adds up to a runaway engine caused by spilled return fuel. If fuel entered the air intake from the outside and caused a runaway, the air filter element would be soaked, or have evidence of fuel wetness at a minimum.

 

[fritza2tt]

Gary, the fuel return line may have dried out from age. It finally must have vibrated loose and then slipped slipped off. No excessive fuel pressure was involved. When I reconnected it, the tractor started normally and worked for several years without a problem. It had nothing to do with the fuel injection pump.

 

[Tx Jim]

Tx Jim, there was no Diesel-soaked air cleaner present. Try to visualise this: you are in the field bush-hogging. The engine is running between 1,500 and 2,000 RPM. Suddenly the fuel return line slips off and fuel ''dribbles' down behind the tank in front of the radiator cooling fan. The fuel is sprayed and sucked in by the fan, mixes with the air and forms a combustible fuel air mixture.

Fritz
If the air cleaner elements weren't soaked please tell me how the fuel got to the intake manifold??????
Envision this:: the fan is behind the fuel tank and air cleaner inlet. If the fan was pulling this supposedly spraying diesel through the radiator did the diesel fuel mysteriously swirl around and move back forward and get sucked into the screens on each side behind the radiator???????? NO, the spraying diesel got blown on the tractor operator by the FAN. I hope you have a nice day. Jim

 

[Tx Jim]

TX Jim, What was the bust pressure on the old pencil injectors? Can稚 remember.

I got this info off another tractor site that I frequent.
I have a sm-2045 and there is around 15-20 different part numbers with most of them opening 2750-2850 new and 2550-2650 used,but some are up to 3350-3450 new and 3150-3250 used. with a part# i could tell you the correct specs.

 

[jd110]

I'll stay away from the ongoing discussion of the cause of the runaway. I want to say that to assess the damage to the engine, I would drop the oil pan first and check crankshaft bearings. If any of the bearings are damaged and crank is damaged, the repair will likely be considerably more than $2700.00. I would also suggest sending injection pump and nozzles out for repair. The runaway condition, if not caused by the pump, could have caused damage to the pump during the runaway. I wouldn't want to chance having a newly rebuilt engine damaged by a bad pump. Also, bad injectors can definitely cause an increase in return fuel flow.

 

[fritza2tt]

jd110, his sounds like good advice. I'll have to copy it and take it with me when I bring in the tractor. Did you see that I was able to start the tractor after it ran away? It started normally but I could tell not just from the noise, that one cylinder was missing. Only ran it for a few seconds. I
don't think I have a problem with the fuel injection pump and I was thinking that a compression test would provide a clue to the condition of the functioning cylinders. What would be considered normal compression pressure and what would be tolerable? This tractor will not be required to do heavy work again. I'm 83 and need it but for a few more years to haul fire wood with the front end loader and to movce some round bales I still need to sell. The dealer who offered to do the repair talked of changing bearings, pistons, cylinders, wrist pins etc.

 

[jenkinsph]

fritza2tt, jd110 may not respond again but I would heed his advice.

 

[Tx Jim]

I also agree with what jd110 stated. I've seen failing inj pump governor let engine run at erratic rpm's and then the rpm's act normal. Only way to really know condition of pump is to look inside. Also a bad injector can make a knocking sound.

 

[fritza2tt]

I'm learning a lot on this thread. A leaking fuel injector sure enough would be a good reason for the engine to knock. What it boils down to is that an unknown amount of damage was done when the engine ran away and not knowing how much more it would cost, in addition to the $2,700, really makes me pause and search for a better solution. Ideally, somewhere there would be a replacement engine at a reasonable cost. Any one know where I need to look to find one?