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engine trouble

#1

S

starnsrd

I have a 2007 John Deer tractor with a briggs and stratton engine with 508 hours, the oil has been changed every 25 hrs and the oil filter changed
every 50 hrs, the engine runs great for about 1 hour, while the engine is under a load, blades turning, the engine will stall until the blades are disengaged
then runs good again just moving forward, the only smoke i see is coming from the fly wheel when I stop the engine, does not burn oil, any comments would be
greatly appreciated


#2

StarTech

StarTech

Need more info. As my all seeing eye is on the blink as I haven't two pots of coffee yet this morning.

There is a lot different JD tractors and mowers all with different engines.


#3

S

starnsrd

Im sorry failed to mention, its 21 hp OHV Twin V


#4

StarTech

StarTech

Being a V-twin you may have an ignition coil or spark plug failing. They can run fine off load but fail when loaded.


#5

S

starnsrd

the spark plugs have been changed, and both cylinders are firing


#6

I

ILENGINE

starnsrd said:
the spark plugs have been changed, and both cylinders are firing
Click to expand...
At the time of failure or when just running.


#7

H

hlw49

pull the engine blower housing and see if the cylinder fins are clogged up.


#8

B

bertsmobile1

There are way too many things that it could be
None of us feels like rewriting the 200 page B & S manual or the 400 page J D manual
So lets start with the model type & serial numbers from your engine so we know exactly what engine you are having problems with .
There is a lot more to proper engine maintanance than just changing the oil & filters
When was the last time the valve lash was checked ?
at 508 hours it should have been done at least 2 it not 3 times

If I under stand what you are saying, the mower starts fine then cuts fine for about 1 hour then it will stop unless you turn the blades off

So when were the spindle bearings last replaced or even greased ?

If you turn the blades off then back on again does the problem take another hour to reoccur or dose the engine instantly stop ?

If you pull the choke on does it make a difference ? if so what happens ?

After it goes bad how long do you have to leave the mower before it works normally again ?

How old is the battery ?
If you charge the battery overnight does it go longer before giving you problems ?


#9

S

starnsrd

bertsmobile1 said:
There are way too many things that it could be
None of us feels like rewriting the 200 page B & S manual or the 400 page J D manual
So lets start with the model type & serial numbers from your engine so we know exactly what engine you are having problems with .
There is a lot more to proper engine maintanance than just changing the oil & filters
When was the last time the valve lash was checked ?
at 508 hours it should have been done at least 2 it not 3 times

If I under stand what you are saying, the mower starts fine then cuts fine for about 1 hour then it will stop unless you turn the blades off

So when were the spindle bearings last replaced or even greased ?

If you turn the blades off then back on again does the problem take another hour to reoccur or dose the engine instantly stop ?

If you pull the choke on does it make a difference ? if so what happens ?

After it goes bad how long do you have to leave the mower before it works normally again ?

How old is the battery ?
If you charge the battery overnight does it go longer before giving you problems ?
Click to expand...
no need to re- write the manuals. i can get those myself, the spindals were changed 2 years ago, and greased every 50 hrs since then, the battery is 4 years old, changing the oil does not keep an engine running, I agree, needs gas in the tank, how you like those apples. but you mention checking the valve adjustment, should be done every 200 hrs, has not been done, i'll check on that, thanks for your advice


#10

B

bertsmobile1

We all approach the forum differently
I for one have a set method.
I ask questions that help me and others to diagnose the problems presented and some times even give the poster tests to do.
When the questions get answered and the test results posted then a diagnosis can be attempted or further testing requested.
Your problem could be electrical , mechanical , thermal or fuel related or even a combination of any or all of them .
I could probably write down better than 30 things that could be at the root of your problem but as perviously mentioned, no intention of writing a service manual.
starnsrd said:
the spark plugs have been changed, and both cylinders are firing
Click to expand...
But are they still firing under load after an hour ?
Did you install a pair of in line spark testers to confirm this ?
Do they continue to fire right up untill the engine stops turning or do they stop firing before the engine has wound down ?

I asked 6 questions, you answered 2 of them
If you don't help us we can not help you
It is as simple as that


#11

StarTech

StarTech

Only one problem with those inline spark testers. They indicate spark even when the plugs are shorting to ground. And plugs with cracked insulators can short when hot. Plus testing plugs out of the engine's compression zone only confirm they fire outside the compression zone. They still can misfire under compression.

I even had one plug a few years ago to cause dieseling under compression load at full throttle only which push beyond the coil's rpm limiter.

It takes experience to diagnose some problems. Yes basic problems are easy but there are unique problems sometimes.

On top of that just because a plug is new doesn't mean it is good. That is why you must a known good plug for testing.


#12

Hammermechanicman

Hammermechanicman

You are correct the neon inline testers do not test the plug itself. When troubleshooting a problem like this i would put in new plugs and use the the inline testers and run till the problem shows up and see if the testers show a problem. That is why you really need inline neon testers and spark gap testers. Of course most DIY's don't have them.


#13

B

bertsmobile1

I think you are both missing the point of using the tester
IT is there to see if the problem is electrical , mechanical or fuel
A first line test to eliminate the magnetos and mower wiring
New plugs will not help you find a coil or bridge wire that is faulty .


#14

StarTech

StarTech

They only indicate if the coils and trigger circuits are working and that the kill circuit not grounded. It tell if the coils are shutting due to heat soaking due will not tell if the plugs are actually firing or not. So a problem can still be electrical in nature when plugs are failing themselves. As I said new plugs don't always mean good plugs which why you need to be testing with known good plugs.

Unless spark plugs are firing by something other electricity which btw they can but still need electrical juices to get them hot enough.


#15

Hammermechanicman

Hammermechanicman

bertsmobile1 said:
I think you are both missing the point of using the tester
IT is there to see if the problem is electrical , mechanical or fuel
A first line test to eliminate the magnetos and mower wiring
New plugs will not help you find a coil or bridge wire that is faulty .
Click to expand...
We are doing basically the same thing. Troubleshooting, eliminating things that are working until you find something not working properly. New plugs eliminate one variable then using the neon testers can identify or eliminate a coil problem WHILE the engine is running poorly.

I have had customers bring in equip and say it has spark by holding the plug to engine and pull rope. Neon tester shows spark. Put plug in and neon tester shows spark but plug arcs under compression and engine won't run. Bad plug. We can easily test coils but don't believe any of the clowns on utube about testing a sparkplug with a meter. Since i don't want to spend $1K on an aircraft sparkplug tester i substitute a new $3 plug and assume the plug isn't the problem. Always a first time but so far all the new plugs have been good.


#16

StarTech

StarTech

I wish that was the case with new plugs here. I have seen bad ones right out the package. Not usual if I buy the box full, just individual plug purchases.

As you know Hammer plugs can fail under compression which I proved to one customer this year. When he saw the plug outside the engine he said it was good but I went and pulled a known good and the engine fired right up. He is now a believer that plugs can be even when spark outside the engine.

I just took a couple Oregon plugs apart to find out the insulators where cracked so bad that one plug was broken in two and only held together by the crimped plug shell.


#17

Hammermechanicman

Hammermechanicman

I have seen quite a few of the chineese no name plugs in the amazon and ebay tune up kits fail within minutes of running. These always go in the trash and it gets a champion of NGK plug. Lots of folks loke to hate on champ plugs but B&S uses million or so
every year in new engines.


#18

smhardesty

smhardesty

StarTech said:
I wish that was the case with new plugs here. I have seen bad ones right out the package. Not usual if I buy the box full, just individual plug purchases.
Click to expand...

I just experienced that today. I was working on a Briggs motor on a push mower. It was a simple tune and service. I needed a new air filter and an RJ19LM plug. Made a quick trip to pick the stuff up. Came home, checked the gap to ensure it was correct, shoved the plug in, connected the wire, and spent the next 5 - 10 minutes pulling and cussing. Wouldn't even try to fire. I eliminated things one by one and, on a whim, stuck the old plug back in. One pull and she fired and ran.

I'll be taking this "new" plug back tomorrow. I'm not really sure why I thought to try the old plug, but I'm sure glad I did. LOL! So, yeah, a new plug does NOT mean a good plug.


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