My 1958 model 851 diesels when turning off ignition. Last time I was on my prperty(240 miles away) I thought I would check to see if the timing was perhaps off. Unfortunately the the Craftsman timing light(haven't used in many years) was not operational any more. I know that it could be a carbon buildup problem. But I want to see if perhaps changing the timing might cure this problem. Without using a timing light which way should I adjust the distributor, lower rpm's or higher rpm's? I do have a Craftsman engine analyzer with DWELL check, perhaps that can also be used? How? Thanks. Joe in NYC.
- Thread starter Joe)NYC)
- Start date
rustred
Well-known Member
as with any engine when you turn the dist. the same direction as rotor turns this retards the timing, usually retard about 2 to 4 degrees for dieseling. but the biggest thing is the idle, you set it as low as possible to cure dieseling.most time you dont need to readjust timing, just keep it at the factory spec.
Rustred, I've had the idling set down as low as 500rpm. But when running the mower it is much higher. Before I shut down the tractor I also tried to run it at idle for a couple of minutes with the same dieseling result. I will now try retarding timing some(by ear) and see what that buys me. Thanks for the info.
Anonymous-0
Well-known Member
If you use the search engine "ignition dwell" it will explain how to do it..... also "engine running on after switching engine off " particularly No. 7 & 8...mostly caused by a carbon hot spot...
Joe:
Asuming that the specified spark plugs are installed, dieseling of a gasoline engine upon shut down is almost always caused by an idle adjustment that is too high. Most likely, your engine will not diesel upon shut down if the engine is allowed to return to the specified 400 RPM before shutdown.
Retarded timing will cause the exhaust to overheat, which will lead to more serious problems eventually but will have little effect upon dieseling upon shutdown. Note: Even if the static timing is properly set at 4 degrees BTDC at 400 RPM or less and the mechanical advance mechanism is not working, the timing will be seriously retarded at operating speeds.
Several times in the past I have posted a static timing procedure for accurately setting ignition timing that is performed with the engine not running and without the use of any tools aside from a wrench to loosen/tighten the distributor. Search the archives and you should find it.
Dean
Asuming that the specified spark plugs are installed, dieseling of a gasoline engine upon shut down is almost always caused by an idle adjustment that is too high. Most likely, your engine will not diesel upon shut down if the engine is allowed to return to the specified 400 RPM before shutdown.
Retarded timing will cause the exhaust to overheat, which will lead to more serious problems eventually but will have little effect upon dieseling upon shutdown. Note: Even if the static timing is properly set at 4 degrees BTDC at 400 RPM or less and the mechanical advance mechanism is not working, the timing will be seriously retarded at operating speeds.
Several times in the past I have posted a static timing procedure for accurately setting ignition timing that is performed with the engine not running and without the use of any tools aside from a wrench to loosen/tighten the distributor. Search the archives and you should find it.
Dean
John Smith8N
Member
You've already received good advice on correcting the problem. In the mean time, when you go to turn off the tractor, leave it in gear, hold the brakes, ease the clutch out until it starts to pull the engine down a little, and turn off the key. That will stop the potentially damaging run-on condition you're experiencing.
Thanks for all the replies. Just want to mention that I only put in new plugs and cables but did not change the timing. I also had been idling engine at its lowest position before shutdown. Also I did use the example set out by Jon Smith for shutdown. It took a bit before it shut down. I will have to get me a new timning light and read up on the archives for more info. Thanks.
Joe(NYC).
Joe(NYC).
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