John Deere 115 mower - Briggs Engine
- Thread starter N00bie
- Start date
When you try to restart, it does fire, it just wont start until cooled. So I can guarantee there is spark. BUT, maybe it is failing?
Going to replace magneto as not know what else to do
Before dumping lots of parts, try spraying carb or brake cleaner into the carb when hot and see if it wants to start. If so, and you have eliminated a fuel issue, then it's probably carb related. If not, then I would think spark related. If you have not actually replaced the spark plug, then try that 1st.
It always tries to start. As I said, it will fire (combustion) as long as you have key turned to start and will even run for a second or so but then dies. It is definitely heat related. Fuel would not be affected by heat or maybe a failing magneto?
Not going to dump lots of parts but may be fed-up and dump the mower.
Sounds most likely like a coil failing.
The typical way they fail is they will get hot in about 12 to 15 minutes and it will just shut down like you turn the key off. It will not restart normally until it cools off for hours and will run the same amount of time again and you can do this every single day running for about 12 minutes. Sometimes you let them cool off 4 or 5 minutes they will fire back up and only run for a couple of minutes but not normally.
The way to test is to get it running and when it dies immediately pull out the spark plug and check for spark. If you have no spark then you likely have a bad coil.
The typical way they fail is they will get hot in about 12 to 15 minutes and it will just shut down like you turn the key off. It will not restart normally until it cools off for hours and will run the same amount of time again and you can do this every single day running for about 12 minutes. Sometimes you let them cool off 4 or 5 minutes they will fire back up and only run for a couple of minutes but not normally.
The way to test is to get it running and when it dies immediately pull out the spark plug and check for spark. If you have no spark then you likely have a bad coil.
MikeStihl046
Forum Newbie
- Joined
- Dec 1, 2022
- Threads
- 0
- Messages
- 2
I agree with the guys saying is the coil. Coils will start to fail and will start to cause problems by not supplying a good spark or no spark at all when they warm up. Run it until it dies then test your coil using a multimeter. Your looking for the same reading been the boot and the pick ups and the kill wire connection and the pick ups. Be sure it's good and warm first. If it's not it may still read right even if it's bad. You don't have to pull it to test. Just pull the boot off the plug and pull the kill wire from it's connection so you can excess the tab. So run it until it dies, have you plug boot pullers and your multimeter on you. As soon as it dies check the resistance between those two locations, the boot and pick ups, then the tab where the kill wire connects and the pick ups. If they read the same your coil is good. If they don't read the same then it's bad. But I would almost be willing to guarantee that's the issue. The coil is heating up and the spark is degraded.
bertsmobile1
Lawn Royalty
- Joined
- Nov 29, 2014
- Threads
- 65
- Messages
- 24,995
Nothing gets ruled in or out till it has been tested
For instance a loose inlet valve seat could produce the same symptoms
A leaking manifold gasket can do the same
As can a leaking head gasket
So you start with the mechanical or with the fuel
For me I pop a SHORT shot of carb cleaner down the plug hole
Engine fires = spark is good
Next do the same down the carb
engine fires = valve timing is good so that suggests fuel and the last bit is the carb solenoid
You can do a quick & dirty test by holding it while turning the key on & off
Then it is off with the rocker cover and check the valve lash
I do this after the carb cleaner because most are lathered with silly cone which takes forever to get off & be replaced with a gasket .
After the valve lash is set I rotate the engine and watch the valves
They are the same, their position in the head is the same & the cam lift is the same , these can all be verified with a simple visual inspection
As this engine is not running the next check is the head gasket - valve seal - rings by doing a leak down test and using ones ears for where the whooshing air is coming from
If all of these test OK then you are left with the magneto
You can use one of those very expensive variable gap jobbies or just hold the spark plug ( using insulated pliers ) about 1/4" off the head while you crank the engine
A good magneto will cause the plug to spark between the electrodes and from the engine to the outside of the plug from 1/4" to 1/2" away from the head
Do this test kill wire on & kill wire off , if the wiring is good then it should be the same
Now if you suspect the magneto try the above test with engine stone cold and again with engine hot
The distance a spark throws should be almost the same hot or cold ( hot will be a little less but not much )
If you have a bit of 1/4" metal bar, you can shove it into the spark plug cap
With the lower resistance a good mag will throw a spark from 1/2" to 1" away from the head
Very rarely the plug cap will go bad but you can sort of test this by pushing the cap harder onto the HT lead or screwing it in 1 more turn
I find those caps with the full metal shield to be the worst .
Sounds like a lot but it is less than 1/2 hour
For instance a loose inlet valve seat could produce the same symptoms
A leaking manifold gasket can do the same
As can a leaking head gasket
So you start with the mechanical or with the fuel
For me I pop a SHORT shot of carb cleaner down the plug hole
Engine fires = spark is good
Next do the same down the carb
engine fires = valve timing is good so that suggests fuel and the last bit is the carb solenoid
You can do a quick & dirty test by holding it while turning the key on & off
Then it is off with the rocker cover and check the valve lash
I do this after the carb cleaner because most are lathered with silly cone which takes forever to get off & be replaced with a gasket .
After the valve lash is set I rotate the engine and watch the valves
They are the same, their position in the head is the same & the cam lift is the same , these can all be verified with a simple visual inspection
As this engine is not running the next check is the head gasket - valve seal - rings by doing a leak down test and using ones ears for where the whooshing air is coming from
If all of these test OK then you are left with the magneto
You can use one of those very expensive variable gap jobbies or just hold the spark plug ( using insulated pliers ) about 1/4" off the head while you crank the engine
A good magneto will cause the plug to spark between the electrodes and from the engine to the outside of the plug from 1/4" to 1/2" away from the head
Do this test kill wire on & kill wire off , if the wiring is good then it should be the same
Now if you suspect the magneto try the above test with engine stone cold and again with engine hot
The distance a spark throws should be almost the same hot or cold ( hot will be a little less but not much )
If you have a bit of 1/4" metal bar, you can shove it into the spark plug cap
With the lower resistance a good mag will throw a spark from 1/2" to 1" away from the head
Very rarely the plug cap will go bad but you can sort of test this by pushing the cap harder onto the HT lead or screwing it in 1 more turn
I find those caps with the full metal shield to be the worst .
Sounds like a lot but it is less than 1/2 hour
Yeah, I was convinced it had to be the coil (magneto) so I just replaced it. Made no difference
Might be time to junk the whole mower?