what makes a 4 cycle diesel?

[ghost civic]

I don't feel like joining a forum to get this question answered and Im sure someone on here must know!

I have a husqy riding mower...if I run it for a half or our more (or if the day is really hot) when I shut off the ignition the rpms come down but then it will fire a few more times. I think I counted 6 times one day. Im sure this cant be good for the motor and I think it is refered to as dieseling? The ignition certainly kill the spark, but for some reason the air/fuel mixture being sucked in as the engine slows to a stop is able to ignite on its own.

Is this a sign of rich or lean mixture? Or are there other possible causes? Other than this issue, the engine runs great. Fires right up, will always re-start even if it has been run for a long time and has plenty of power.

 

[Denny]

Glowing hot carbon or too much carbon in the cylinder, also I have seen it happen with too hot of a sparkplug.

Denny

 

[Poboy kartman]

To expand: "dieseling" means the engine continues to run after the ignition quits....

First, there has to be a heat source for this to occur, and as previously stated,almost invariably it's carbon deposits.

Secondly, although not absolutely necessary, usually indicates an engine running hot....most likely lean and/or timed too far advanced.

In itself....dieseling is not very harmful....despite the sound...but the conditions that may be causing it can be doing a lot of damage while the engine is actually running....

 

[itsid]

....most likely lean and/or timed too far advanced.

timed...? how so?

'sid

 

[Shraddha]

pardon Sir..."engine running hot....most likely lean and/or timed too far advanced." what this means.

 

[DirtyDamage]

Simple fix if it's a lot of carbon deposits which are getting hot....Sea Foam to the rescue. Cleans all the carbon deposit of valves, and the cylinder and what not...

 

[mckutzy]

I have heard that putting a small amount of water in the intake when running causes carbon deposits to be removed in the combustion chamber.
It's also how a leaky head gasket is found by the cleanliness of a chambers walls, having a carbon free area, or spark plug(obviously in a gasoline engine).

 

[Poboy kartman]

pardon Sir..."engine running hot....most likely lean and/or timed too far advanced." what this means.

What 'sid was getting at is that these engines do not have adjustable timing. Sooooo.....really...the only way it's going to get out of time is:

#1: Bent flywheel key

#2: Sheared flywheel key

#3: No. (or offset) flywheel key

Granted, these are a bit remote....but the symptoms match....so it beared mentioning.

 

[ghost civic]

Leans seems unlikely as it smells like it runs a tad rich if anything. But I can also feel a fair bit of heat coming off of it while riding...maybe that is normal, maybe not. I have used rider mowers before, but they were always fairly new ones. This one is from '97-'99.

But, I did buy this well used and have run it as I received it.
I think I will try sea foam and a new spark plug and then go from there.

I really cant complain...paid $150 for it...put on $30 worth of new blades and other than having to put air in the rear tires each time I use it I haven't had to touch it.

I have a white outdoor rider that I also just bought...for $100! I put on a new deck belt, will need the PTO belt as well and should have the blades replaced. But the motor/trans work great.

 

[mckutzy]

Sparkplug???

Are we talking about the type of engine(diesel) or the effect(dieseling)?

 

[BirdFanatic]

Seafoam will knock some of the carbon off but im not sure how you do it with a diesel .You can also change the oil to keep it a little cooler synthetic runs cooler but you need to get a thicker kind .

 

[crazykart]

They're talking about the effect of "dieseling" and not an actual diesel motor.

 

[DirtyDamage]

Seafoam will knock some of the carbon off but im not sure how you do it with a diesel .You can also change the oil to keep it a little cooler synthetic runs cooler but you need to get a thicker kind .

*facepalm*

 

[ghost civic]

A oil change probably would be a good idea.

 

[Poboy kartman]

An oil change is always a good idea.....but probably has little to do with the problem....but hey!!!!.........A low oil level very well could...as it's also a thermal coolant to an extent.

 

[itsid]

They're talking about the effect of "dieseling" and not an actual diesel motor.

thank you..

I know the effect.. we just don't call it dieseling in germany..
that's what tripped me off here

Anyways, a sheared key, even if unlikely is indeed not impossible;
just like Doug said...

If you make a plug reading to get an idea of your mixture;
that could at least rule one out

So, when engine hot, kill ignition, and remove plug, then post a pic of it's business end

'sid

 

[crazykart]

thank you..

I know the effect.. we just don't call it dieseling in germany..
that's what tripped me off here

'sid

Lol, ya mckutzy and Birdy seemed to be a tad lost on what exactly was being discussed.

 

[itsid]

Lol, ya mckutzy and Birdy seemed to be a tad lost on what exactly was being discussed.

Well a lost Cam.... it's summertime so that's rather common

'sid

 

[crazykart]

Well a lost Cam.... it's summertime so that's rather common

'sid

Haha, wait... he's a Californian...it's basically always sunner there.... so when has he not been lost?

 

[OzFab]

I think that may have been the point