John Deere 520 Disesls

[GMAN]

Got a John Deere 520 and the darn thing diesels(runs backwards) checked timing and installed electronic module still diesels,rebuilt carb,put a manuel shut off on fuel nothing seems to help,would a badly worn cam cause one to act this way?any ideas would be greatly appreciated Gman

 

[wilamayb]

I think the same would apply here as with any internal combustion engine.

Make sure that the engine is idling before killing the spark.

Often a cool down period before killing spark will also cure the problem.

Make sure your engine is not running above 210F since excessive heat can also contribute. It would be better if it ran around 200F

You can use a higher octane gasoline if you are not already.

Lean your idle mixture as much as possible.

Make sure your manifold is set on the summer setting.

Another thing that causes dieseling and detonation is carbon buildup in the combustion chamer.

Strange problems can cause strange symptoms. I'd never say never on the cam but I sure would say I dont think so.

You dont have the only late two cylinder that does this. It happens sometimes and makes a nasty mess of the precleaner bowl if it has one.

As for a single change fix to the problem I'd say start with a higher octane fuel if you dont already use it. Coupled with the other things I mentioned it may or may not cure the problem.

 

[teddy52food]

Put it in high gear & while holding the brakes use the clutch to lug it down before you switch it off.

 

[BushogPapa]

Guess you need to stop it like we always did our OLDER 2-Cylinder tractors..put them in gear at idle and stall them...!!!

No problem with run-on that way..!

My 520 did that a few days ago (for the 1st time), but I may not have cooled it down enough..I had noticed that the idle speed seemed a little high at 700 that time..I usually have it idle around 450 to 500..

Ron..

Ron..

 

[buickanddeere]

How about resolving the problem instead of bandaiding the symptoms?

 

[[email protected]]

One thing that will contribute to the "dieseling" of the engine is excessive carbon build up. Carbon will retain heat that can, and does ignite fuels when the compression stroke squeezes the air and fuel mixture. There are additives that you can mix with fuel, but I warm the engine and remove the plugs. Get some auto tranny fluid in the plug holes and roll the engine over with the plugs out. This will coat the build up and help remove it. After 10 minutes crank the engine over once again and reinstall the plugs. Fire it up and drive it for a few minutes.

 

[fixerupper]

Check the ignition timing. Late timing will make it diesel. Pull the throttle all the way back and let it coast down to idle speed before shutting it off. A lot of people aren't used to the slow idle speed of a two lunger so they shut them down with the engine running too fast and the throttle part way open. Jim

 

[BushogPapa]

I have seen this done..

With a fully warmed engine, POUR a glass of water down the carb..!!
You won't believe how much carbon will come out the exhaust...
I could not believe it when that mechanic did this.!!
Did not damage a thing...this was on a Chrysler 318..
Dad, twice a year would fill an oilcan with engine oil and pump it into the carb with the engine at 1/3 throttle..as fast as the engine could take it..Boy, what a cloud of Smoke that made..!!
That was more to lube the valves than to de-carbon it..but I suppose it may have done some good in there..
The 1st 4 years we owned the Late Styled "B" tractors, JD always had one in the shop with Burned valves..
When the mufflers rusted off, they never burned another valve.!!
Still run a straight pipe on it..top cut at an angle to the front...not loud at all..just right.!!


Ron..

Ron..

 

[F-I-T]

I do that a lot. Best when I have it good and wramed on the dyno, and it will snort out carbon and embers from the muffler. Burn her in another 20 minutes, THEN do the fresh tune up. Compare the before water, after water, and hten after fresh plugs and timing set. It's generally an impressive improvement. Cant' say enough about having a dyno.

 

[gtx1967jewison]

no to high octane. this engine has very low compression & only needs like 68 or something according to the jd literature. the high octane is a bandaid. also no to the lean mixture, lean idle will increase the problem not decrease it. its too lean at idle is the likely cause.

 

[Brian Jasper co. Ia]

Changing the timing has absolutely NO effect on any engine dieseling at shut down. When you turn the switch off, the ignition system stops sending a spark, takes the timing out of the picture. Glowing bits of carbon is usually the cause, along with higher than normal idle speed. Shooting some water in the intake, or soaking the engine with ATF will help remove excess carbon.