QuestionQUESTION: I have a 1991 John Deere garden tractor with an 18hp 3 cylinder engine that does not shut off right away when the key is turned. The engine continues to run for awhile, but quite roughly. I have inspected the plug wires, replaced the spark plugs and ensured the idle was turned down. If the tractor has not run very long it will shut off OK but after it has warmed up will always run-on. It runs fine, just an issue when shut off. Been putting this off much of the summer so need to look into it this weekend. Any suggestions or direction you can offer would be helpful (carb kit??).
ANSWER: Hello Charles:
I Answered this Question for you Already. In Case you Did Not Receive the Answer, I have Copied and Pasted the Previous Answer for you.
I answered this question on 10/24-25/07
Questioner: Charles
Category: Small Engines (Lawn Mowers, etc.)
Private: No
Subject: engine run-on
Question: Super website, very informative.
Have a 1991 John Deere tractor with 18hp 3cylinder motor that doesn't stop right away when the key is turned off, engine continues to run for a few seconds, roughly but still runs. Have checked the plug wires and replaced the spark plugs. Any direction or advice you can offer before I tackle this run-on problem this weekend would be helpful, been putting it off most of the summer.
Answer: Hello Charles:
Usually on this Model Engine the Problem is Caused by Carbon Built Up on the Piston Tops. This Carbon gets Red Hot During the Engine Operation and Causes Dieseling/Run On. The Newer Engines have an Anti-Dieseling Solenoid that Prevents the Gas from Entering the Carburetor Jet and the Engine Once the Ign Switch is Turned to the Off Position and No Gas Enters the Cylinders to Allow the Dieseling/Run On. You can View a Breakdown/IPL of the Mower at this Site Addy, http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.H and Enter the Model Numbers and Click Find. Then Select the Sectional File. Then Select the Section of the Mower you Wish to View Online. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.
Good Luck
Respectfully
John
PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 9pm EST (US). My New Day Starts then. Thanks.
Respectfully
John
PSS: I Forgot to Ask; If you Allow the Engine to Idle for 2 or 3 Minutes Before Shutting it Off, Does this Dieseling/Run On Occur? Thanks.
Respectfully
John
---------- FOLLOW-UP ----------
QUESTION: sorry if I duplicated the question, never got your first reply. Likely my fault as not too handy with computers. Even after a couple minutes of idling the engine will still run-on(diesel) if it has been running for some time.
If this is the carbon buildup you suggest does that mean removing the head or will the combustion chamber cleaners on the market work for this? Thanks.
AnswerHello Charles:
No Worries about the Duplicate Question. It Happens at Times that Questioners Do Not Receive the Answers. Combustion Chamber Cleaners May Work. I Would Give them a Try First. If they Do Not Help the Situation, then Removal of the Heads and Cleaning the Piston Tops Manually is Required. You Did Not Say if the Problem Occurs if you Allow the Engine to Idle for a Few Minutes before Shutting the Engine Off? I Assume it Still Diesels. If you Hit a Snag or this Does Not Correct the Problem, then I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. Thanks.
Good Luck
Respectfully
John
PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 9pm EST (US). My New Day Starts then. Thanks.
Respectfully
John
