John Deere Engine Miss

MBDiagMan · Nov 13, 2013

This is not related to a mower, but given the small engine savvy in this forum, I hope you guys won't mind commenting on the problem I'm having with my John Deere Gator 825i. I have a reasonable amount of experience troubleshooting EFI car and truck engines.

This buggy has an 825cc. Chery, 3 cylinder EFI engine. It has individual coils on the end of the engine. There is no indication of a code being set, but although my scanner will connect to the connector under the dash, it turns out that John Deere has proprietary software so my scanner won't work.

One month after the warranty expired, it developed a missing cylinder. I pulled the plugs and found the center one fouled. I cleaned it and the miss went away temporarily.

I then used a stethoscope while it was missing and could hear all the injectors clicking normally. Although in my fifty years of messing with engines, I've only seen one spark plug that was actually bad, I swapped the number one and two spark plugs and the foul stayed with the center cylinder.

I then swapped the coils between number one and the center cylinder and gave it a hard run. After it warmed up real good it began missing. I brought it back to let it cool before pulling the plugs and thought sure that I would see the number one plug fouled instead. It had been intermittently running well, and what I found was traces that the center cylinder had tried to foul, but couldn't confirm.

I plan on giving it another hard run to see if I can get a consistent foul so that I can confirm which cylinder is now fouling, but at this point it appears that the center cylinder is the culprit even with the swapped coil, but remember, I have not totally confirmed this.

Also, when running it at speed, when the miss develops, I get a popping and snapping from the exhaust, which seems to indicate that unburned fuel is making it into the exhaust and causing this.

Any experience with a similar situation?

Thanks for sharing your savvy and experience.

Restrorob · Nov 13, 2013

Think I'd be performing a compression/leakdown test before jump'n into the efi-ign part of it, You could have a tight valve which could cause "popping and snapping" out the exhaust after warmed up...... But adjusting these valves aren't as easy since they use different thickness shims.

Compression/leakdown test cold then after skipping starts......

MBDiagMan · Nov 14, 2013

Thanks restro.

I'm taking a short vacation and probably won't get back to it until late next week. I think I might do a cold and hot compression test before running any more. I wouldn't want to toast a valve if it's too tight.

Do you know a good source for valve adjustment information for these engines?

Thanks again for your help!

Restrorob · Nov 14, 2013

MBDiagMan said:
Do you know a good source for valve adjustment information for these engines?

Sorry...... I sure don't, Deere is kinda hush on what they share openly for free......

You can check this board out; http://www.johndeeregatorforum.com/forum/forum.php

I did see a couple Deere techs post'n on there that may be able to help......

herler · Nov 14, 2013

It's not a John Deere engine.
John Deere doesn't make engines.
They assemble the machines, I believe they manufacture the frame (which is to say, they weld the individual pieces together and powder coat it), and they might make one or two other bits but for the most part every thing their machines are made out of is manufactured by someone other than John Deere, they simply order it up and when they have all the parts, they run the frame down the assembly line where workers or robots attach all the individual components until they have a complete machine at the end.

Just for example, the tires are probably made by Kenda.
And maybe not but I guarantee they're not John Deere tires.
Because John Deere doesn't make tires.
And they don't make engines either.

Hence it's not a John Deere engine.

That having been said...
I don't know nothing about this machine you speak of.
But you brought it in here.

Restrorob · Nov 15, 2013

Thanks for the school'n herler......

No one said that was a Deere engine...... :nono:

Now it's your turn....... When Deere buy's engines from other makers they also buy the rights as well, This makes Deere the sole proprietor for that spec engine. They do this so end users have to go back to them for parts and repairs and why it's hard to find free repair info...... They want to SELL you a service manual, It's all about $$$$$$$$

To prove the point, I'm a Kawi engine dealer and can look up parts and repair manuals for any engine on my dealer's site......EXCEPT Deere spec engines......

Also, Deere is known to have engine makers spec engines for them only therefore some parts from a non Deere spec engine will not interchange......

MBDiagMan · Nov 15, 2013

Yes, the engine is made by Chery in China

(explains alot) and is a model number 372.

Again, I appreciate the help. When I get back from vacation I'm going to do a cold and then hot compression check. If it does indeed have a valve too tight, I don't want to run it much for fear of burning a valve.

If it does indeed appear that there is a compression problem, I will figure out how to remove the cam cover and check valve adjustment.

I will post a conclusion whatever it turns out to be so that maybe it can help someone else along the way.

MBDiagMan · Nov 20, 2013

I did a cold comp test this morning. Got up to 190 on all cylinders. Ran it a few miles, the miss developed. Checked while hot and got about 180 on one and three, but only a little over 150 on number two.

I guess it's time to find valve adjustment specs.

Thanks very much for putting me onto this Restro!

Restrorob · Nov 20, 2013

MBDiagMan said:
Thanks very much for putting me onto this Restro!

I get lucky sometimes......

I've seen a couple new Chinese single cylinder engines that would shut down a few minutes after starting, I found tight valves......

MBDiagMan · Nov 21, 2013

I can't find any tech info on this engine. I am going to remove the cam cover and see what I find. I should be able to use feeler gauges to determine what the valve clearances on the other two cylinders are and then see if I can set the center cylinder valves to match them.

I don't know until I look at it, but maybe the adjustment will involve removing a shim rather than adding them. If not, I'll try to find the shims.

I hope to get to this on the weekend.

Restrorob · Nov 22, 2013

MBDiagMan said:
I don't know until I look at it, but maybe the adjustment will involve removing a shim rather than adding them.

I don't know that there's more than one shim in each bucket, You may have to measure the one that's in it now and figure what thickness will be needed to get you to the proper spec......

#27 is the shim and I added the different sizes, You'll likely end up at your local Deere dealer if you need any;

MBDiagMan · Nov 23, 2013

Thanks VERY much Restro. If I had not seen this I might not have figured out where the shim is. I sort of expected a shim under a rocker stand or something. I hope I don t have to remove the cams to access them.

My wife and I are going to town for our weekly shopping and errands. I am hoping it will be a little warmer when I get back so I can pull the cam cover.

This is extremely helpful and I appreciate very much you taking time to find and post it.

Restrorob · Nov 23, 2013

Well, It's been over 30 years since I worked at a motorcycle shop doing this style valve adjustments...... I just can't rattle the brain enough to remember if the cams had to come out, But I want to think they do since looking at the breakdown......

MBDiagMan · Nov 25, 2013

Thanks for further response Restro.

I too believe the cams will have to come out. We had stiff North Winds that made it uncomfortable in my tin barn converted to shop type building. We have an ice storm today. I will be off Wednesday through the following Sunday, so I hope to get a chance at it then.

If the cams do have to come out, I will have to find a manual somewhere to make sure I keep everything in time.

If the cams do have to come out, it sure does cast this engine in a bad light as far as I'm concerned. It will be a pain in the neck to deal with.

BTW, is that item 27 the cam follower friction surface?

Restrorob · Nov 25, 2013

MBDiagMan said:
is that item 27 the cam follower friction surface?

Yes...... You may order manuals right from Deere *OUCH*, Have your unit serial number handy; https://techpubs.deere.com/products/ProductResults.aspx

MBDiagMan · Nov 25, 2013

Thanks Restro! You da' man!

MBDiagMan · Dec 1, 2013

I got the manual and have pulled the cover. The shim is changed by rotating the engine such that the cam opens the valve after having rotated the sleeve below the shim to expose a notch. A special tool is put into the notch that keeps the valve open while rotating the cam so the heel is down. You then use a pick to work the shim out.

A couple of valves are slightly tight, by only a thousandth, but I will get them to spec. I ordered the tool and it will be a week before I get it. The shim is indeed the cam follower surface.

MBDiagMan · Dec 2, 2013

Restro,

After getting a chance to read the manual further, I discovered that the valve lash spec's are:

Intake .007" +/- .002"
Exhaus .010" +/- .002"

The exhaust valves are right at .010" while the Intakes are a tight .006", which is still within spec.

Regardless of valves being adjusted within spec, the fact remains that the hot compression on that cylinder is going down from 190 to 150.

Do you think I'm wasting my time, putting those intake valves to .007"?

Thanks VERY MUCH for sharing your time and expertise.

Restrorob · Dec 2, 2013

Well..... The idea was to check the valves, You've done that and they are with-in the book spec. so no I wouldn't bother them. A cylinder leak-down test may show a ring issue.....

MBDiagMan · Dec 2, 2013

Thanks for keeping me between the curbs on this Restro. You're right, there's no reason to screw with the valves. I will do a leak down and listen for where I hear the escaping air.

Do you think that there is any chance it could be the headgasket?

Gotta love a Chinese engine.

John Deere Engine Miss

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