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mower starts only when spark plug connection is removed but near (picture attached)

#1

S

stevenisam

Hi All,

I have a craftsman mower with a Briggs & Stratton engine. This is pretty old mower. This year I changed the spark plug and since then it needs a starter fluid to start. Today it wouldn't start, so i removed the spark plug, cleaned it and sprayed the starter fluild into the cylinder and it started. Only then I realized that I didn't connect the spark plug wire. It was running with the wire right next to the spark plug. Once i connect the spark plug, it never starts.

it starts if I remove the spark plug connection and it won;t start if I connect. I do understand about IC engines to some extend. Any help is much appreciated. Pictures attached.

Thanks in advance,

Attachments







#2

B

bertsmobile1

That is because you have either the wrong plug or the plug has gone bad.
Run the engine for about 10 minutes then cut off the fuel supply to stop the engine.
Replace the plug lead & try again.
If no joy double check the plug.
Most engines with a hall effect triggered magneto take a resistor plug where as points ignitions generally use a plain plug ( no R in the grade ).


#3

EngineMan

EngineMan

That engine if its a 2-16HP should have a Champion CJ8 or J17LM plug 16-18HP will have a RJ12 plug.


#4

S

stevenisam

bertsmobile1 said:
That is because you have either the wrong plug or the plug has gone bad.
Run the engine for about 10 minutes then cut off the fuel supply to stop the engine.
Replace the plug lead & try again.
If no joy double check the plug.
Most engines with a hall effect triggered magneto take a resistor plug where as points ignitions generally use a plain plug ( no R in the grade ).
Click to expand...

Thank you, I will probably replace the plug and try as you suggested. I also notice that there's black smoke coming since I changed the plug.


#5

S

stevenisam

EngineMan said:
That engine if its a 2-16HP should have a Champion CJ8 or J17LM plug 16-18HP will have a RJ12 plug.
Click to expand...

Thank you for the reply, its a 3 HP engine. it had a CJ8 plug and I replaced it with another CJ8. Attaching the picture of engine

.IMG_20180603_101423 (1).jpg


#6

cpurvis

cpurvis

By holding the spark plug wire at a distance, in effect, you have created a "booster gap" spark plug: http://firetrucksandequipment.tpub.com/TM-5-4210-230-14P-1/css/TM-5-4210-230-14P-1_615.htm


#7

EngineMan

EngineMan

If you have black smoke coming out then have the carb check and cleaned.


#8

B

bertsmobile1

Modern fuel, which is nothing like petrol , is very conductive at cylinder pressures.
Thus the spark will run down the side and ground out at the bottom of the insulator rather than jump the gap.
Holding the lead off the plug forces the voltage to build up to a higher amount before it can get to ground through the plug thus when the higher voltage hits the electrode it will jump the gap & fire the engine.
If your carb is flooding the engine then the plug will always be wet.
An old adage goes
Most ignition problems start in he carburettor
Most carburettor problems start in the ignition.

A magneto does not produce a fixed voltage, the voltage varies with the speed the magnets pass the coil .
Most of them will spark well before peak voltage is reached.


#9

Boudreaux In Eunice La.

Boudreaux In Eunice La.

Steven you have a great engine right there, that most people would pay good money for..........


#10

Boudreaux In Eunice La.

Boudreaux In Eunice La.

Steven can you post a pic of the mower it's on ??? I remember the old Yazoo mowers with the horizontal Briggs on them.......

Great bullet proof mowers......

Plus Tard Mon Ami ~!~!


#11

S

stevenisam

cpurvis said:
By holding the spark plug wire at a distance, in effect, you have created a "booster gap" spark plug:
Click to expand...

Thank you, that's a good read.


#12

S

stevenisam

bertsmobile1 said:
Modern fuel, which is nothing like petrol , is very conductive at cylinder pressures.
Thus the spark will run down the side and ground out at the bottom of the insulator rather than jump the gap.
Holding the lead off the plug forces the voltage to build up to a higher amount before it can get to ground through the plug thus when the higher voltage hits the electrode it will jump the gap & fire the engine.
If your carb is flooding the engine then the plug will always be wet.
An old adage goes
Most ignition problems start in he carburettor
Most carburettor problems start in the ignition.

A magneto does not produce a fixed voltage, the voltage varies with the speed the magnets pass the coil .
Most of them will spark well before peak voltage is reached.
Click to expand...


Thank bertsmobile, that's a sound explanation. Will keep this in mind about spark plugs.


#13

S

stevenisam

Boudreaux In Eunice La. said:
Steven can you post a pic of the mower it's on ??? I remember the old Yazoo mowers with the horizontal Briggs on them.......

Great bullet proof mowers......

Plus Tard Mon Ami ~!~!
Click to expand...

here is the picture.IMG_20180605_220059.jpg


#14

Boudreaux In Eunice La.

Boudreaux In Eunice La.

Wow you got a good one right there... I love those old reel mowers.... My non'c had one when I was a small kid and couldn't push it..... It was a self propelled of course... That means by your self and no engine......

He bought that thing in the 40's after he got out of WWII........... I wish I had it today.............


#15

S

stevenisam

bertsmobile1 said:
That is because you have either the wrong plug or the plug has gone bad.
Run the engine for about 10 minutes then cut off the fuel supply to stop the engine.
Replace the plug lead & try again.
If no joy double check the plug.
Most engines with a hall effect triggered magneto take a resistor plug where as points ignitions generally use a plain plug ( no R in the grade ).
Click to expand...

You were right, looks like the plug has gone bad. I changed it to another CJ8 plug and it did start with starter fuild. it was still emitting black smoke. I removed the air filter and the smoke disappeared. So looks like the air filter is blocking inflow of air and the gas is not getting enough air to burn. I couldn't find a replacement air filter locally, so went ahead and cleaned it for now. I also looked at the engine replacement parts and found that it needs a RJ19LM plug, so changed the plug to First Fire FF-10 which seems to be the replacement plug for RJ19LM. It still needs a starter fluid when cold but it started on first pull once warmed up.

Like mentioned in this forum, the carb might need a clean up but I am afraid to touch it, so if it works with starter fluid, I will continue to use it.

Thanks again to everyone who pitched in.


#16

Boudreaux In Eunice La.

Boudreaux In Eunice La.

Please don't use starting fluid in your engine... Just use some carb cleaner...... It's easier on your engine....... A kit is cheap and easy to replace .......

Plus Tard Mon Ami ~!~!


#17

Boudreaux In Eunice La.

Boudreaux In Eunice La.

stevenisam said:
You were right, looks like the plug has gone bad. I changed it to another CJ8 plug and it did start with starter fuild. it was still emitting black smoke. I removed the air filter and the smoke disappeared. So looks like the air filter is blocking inflow of air and the gas is not getting enough air to burn. I couldn't find a replacement air filter locally, so went ahead and cleaned it for now. I also looked at the engine replacement parts and found that it needs a RJ19LM plug, so changed the plug to First Fire FF-10 which seems to be the replacement plug for RJ19LM. It still needs a starter fluid when cold but it started on first pull once warmed up.

Like mentioned in this forum, the carb might need a clean up but I am afraid to touch it, so if it works with starter fluid, I will continue to use it.

Thanks again to everyone who pitched in.
Click to expand...

An update would be nice....... How is it running for ya ?????


#18

sgkent

sgkent

put the old plug back in and see if it will run with that.


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