ignition coil
- Thread starter RPM1970
- Start date
Please explain the coil testing procedure.
Set the coil to flywheel gap at 0.010". Use a piece of junk mail or similar.
- Joined
- Feb 19, 2020
- Threads
- 77
- Messages
- 10,228
here is some on coil testing. Be aware heavy reading involved.
Reference Site : http://www.briggsandstratton.com/eu/en/support/faqs/ignitionsystem-
theory-and-testing
Ignition System Theory and Testing
How does the Magnetron Ignition System function? How can it be tested?
Ignition System Theory and Testing
The 1980's ushered in the magic black box, Magnetron™ ignition coil, Briggs &
Stratton's first truly electronic ignition system. Breaker point ignition systems
for most small air-cooled engine manufacturers have totally disappeared over the
last 20 years. In a point style system, the flywheel magnets rotate past the legs
of the ignition armature. The armature itself is made up of two separate windings
of copper wire - the primary and secondary - one wound on top of the other. Basic
physics tells us that when a magnetic field (flywheel magnet) cuts through (moves
past) a conductor (copper wire), a flow of electrons (electricity) is created.
However, electron flow only occurs when we have a complete circuit. This means
that the points must be closed. We're also told that the faster the movement
between the field and the conductor, the greater the output.
Remember science class in grade school? At one point in your school career, an
enterprising teacher wrapped a length of copper wire around a nail and hooked the
wire ends to a dry cell battery. A handful of paper clips was instantly attracted
to the nail and fell away when the battery was disconnected. Electron flow through
a conductor then, causes a magnetic field. When the points close, electron flow
causes a magnetic field to be created around the primary. This field also
envelopes the secondary. The points now open, break the circuit and collapse the
field through the primary. The field caving in on itself is movement just like the
rotating magnetic field of the flywheel. This movement is at speeds much greater
than the flywheel could spin - near the speed of light. The rapidly collapsing
field tears through the secondary winding which has sixty turns of wire for every
one turn of the primary - effectively generating 60 times the voltage created in
the primary. The sum total of this is that the secondary winding can create up to
25,000 volts in some systems, which is used to jump the air gap of the spark plug
and ignite the fuel/air mixture in the combustion chamber.
Now for the black box. Magnetron™ solid state ignition systems, in essence, replace
the mechanical breaker points with a transistor. That is, we replace a mechanical
switch with an electronic one. No moving parts, no arcing, no adjustments and
solid state reliability.
Now that we've got an idea of how it all works, let's look at the meat and potatoes
of what is required to create a good spark.
Flywheel:
The flywheel magnet must generate a sufficient magnetic field to start the chain of
events in motion. A fair test is to hold the flywheel on edge with the magnet
facing up. Place the blade of a 10" #3 (1/4") straight blade screwdriver against
the magnet. Release the screwdriver. The magnet should have enough strength to
hold the screwdriver straight out. If we pass this test, assume the magnet is OK.
Rotational speed:
Remember speed is a factor. The engine must be pulled over at a minimum speed of
250 RPM* before the coil will even think about firing. Thick oil on a winter day or
a heavy parasitic load may cause problems. Customers come into play here as well.
Shorter or elderly individuals may not have the leverage or strength required to
reach the RPM required to activate the Magnetron's electronics. *NOTE: Briggs
service manual has it at 350 rpm minimum.
Spark Plug:
The spark plug is a major element of the equation. A new spark plug may require
around 10,000 volts to jump a .030" gap when the engine is cold. This drops to
just 4,000 when the engine is hot as electrons are more easily emitted from a hot
surface. That's one of the reasons the old vacuum tubes in radios had to warm up
before the radio would work. Electrons are also more easily emitted from a sharp
edge than a round one. A spark plug begins to require more and more voltage as the
edge of the center electrode becomes less defined. And finally, an internal short
or carbon/oil fouled plug simply shunts the high voltage burst straight to ground
with no or insufficient spark. NOTE: It only takes 1,000 volts to jump a 0.025” air
gap in open atmosphere, it takes 10,000 volts to jump the same gap at 120 psi,
therefore an open air spark test in not valid.
(Can't get this through some the thick skulls out there).
NOTE: The spark should be a minimum of 10 Kv (10,000 volts) at pull over speed.
Ignition Coil:
The ignition coil is probably the easiest thing to check and therefore the first
thing to check when embarking upon ignition system troubleshooting. Install the
19368 spark tester between the high-tension lead and a good engine ground. Spin
the engine over (at least 250 RPM) and watch for spark in the tester window. As
simple as it seems, this is a fairly comprehensive test. The tester electrode gap
is .166" wide. Those wise in the way of electrons have calculated that it takes
around 13,000 volts to jump this gap. We need 10,000 to jump the gap on a cold
spark plug. Add it all up and we have voltage to spare. As coil temperature can
aggravate minor coil imperfections that normally wouldn't be a factor, the same
test can be done on a warm engine. Engine quits while running? Hook the tester up
in line with the spark plug and start the engine. When the engine quits, monitor
the window. If spark is present, the problem is not in your ignition coil. By the
way, this test stresses the coil well beyond the demand it would see in operation.
Think about it. We're asking the coil to build enough voltage to jump TWO gaps -
the tester as well as the plug. If your engine starts and runs OK cold and hot,
you've got a healthy ignition coil.
One additional test you can perform. Check the impedance (resistance) of the
secondary circuit at room temperature. Hook an ohmmeter test lead to the spark
plug terminal of the high-tension lead and another to the lamination stack
(ground). Your resistance reading should range between 2,500 and 5,000 ohms. If
infinite (no continuity), an internal open circuit exists. Replace the coil. If
infinite and the engine runs, your problem is an internal break of the high tension
lead, a poor attachment of the spark plug terminal or improper mating of the high
tension lead to the coil. A pin within the coil body skewers the lead. If the pin
does not contact the wire core, there will be no continuity. The coil will often
have enough available voltage to jump the gap, so you see spark. The internal
arcing that occurs within the high-tension lead will eventually create enough
resistance that ignition system performance will suffer. If your resistance
reading is much lower than 2,500 ohms, an internal short exists. Replace the coil.
Now, how about some of those old wives tales that just aren't true.
Rust on the flywheel magnets causes a loss of spark. Not true. A magnetic
field does not care about rust. It has no effect on it. Just can cause clearance problems like binding.
A bright blue spark is best. A yellow/orange spark signifies weak ignition.
Not true. Spark color determines virtually nothing. The hottest spark is
ultraviolet which we can't see. Blue spark is cold in comparison to ultra-violet.
Orange and yellow come from particles of sodium in the air ionizing in the high
energy of the spark gap.
Laying the spark plug against the block and pulling the engine over can
adequately test ignition coil output. Not true. The ignition coil will only
generate enough output to jump the gap of the plug. When under compression, the
plug requires twice the voltage to fire. This check is not an accurate test of the
coil and can be misleading.
An armature air gap that is too wide will prevent spark. Not true. Well, sort
of not true. Briggs & Stratton air gaps cannot be made too wide to prevent spark
providing the coil is healthy and the engine is spun over fast enough. A wide air
gap, say .030" will ever so slightly retard the ignition timing as the magnetic
field takes longer to build within the coil windings.
Ignition coils, particularly Magnetron™ coils, rarely fail. If one is suspect,
perform the outlined checks exactly as mentioned. MOST IMPORTANT: Be sure to
isolate the coil from the equipment wiring harness as well as the engine's wiring
harness. That's right, unhook the ignition grounding lead from the coil itself and
use the spark tester. Many a technician is fooled into replacing a good coil
because the coil grounding lead was shorting out against a piece of sheet metal.
DO NOT attach the tester to the spark plug for this test. The engine may start.
Without the grounding lead installed, you won't be able to turn it off. If the coil
is properly grounded to the engine block, engine speed is at least 250 RPM and the
flywheel magnets are OK, there should be spark present in the window of the tester.
If not, repeat the test double checking your procedure. Still no spark? Then and
only then, replace the coil.
A final bit of trivia - All Magnetron™ Ignition coils have the manufacturing date
code cast into the coil body. The coil manufacturing date will usually be within a
month of the engine's date code. That's an easy way for you to tell if the coil
has been changed before. We use this information to match returned parts to the
engine noted on a warranty claim as well as for internal tracking.
Reference Site : http://www.briggsandstratton.com/eu/en/support/faqs/ignitionsystem-
theory-and-testing
Ignition System Theory and Testing
How does the Magnetron Ignition System function? How can it be tested?
Ignition System Theory and Testing
The 1980's ushered in the magic black box, Magnetron™ ignition coil, Briggs &
Stratton's first truly electronic ignition system. Breaker point ignition systems
for most small air-cooled engine manufacturers have totally disappeared over the
last 20 years. In a point style system, the flywheel magnets rotate past the legs
of the ignition armature. The armature itself is made up of two separate windings
of copper wire - the primary and secondary - one wound on top of the other. Basic
physics tells us that when a magnetic field (flywheel magnet) cuts through (moves
past) a conductor (copper wire), a flow of electrons (electricity) is created.
However, electron flow only occurs when we have a complete circuit. This means
that the points must be closed. We're also told that the faster the movement
between the field and the conductor, the greater the output.
Remember science class in grade school? At one point in your school career, an
enterprising teacher wrapped a length of copper wire around a nail and hooked the
wire ends to a dry cell battery. A handful of paper clips was instantly attracted
to the nail and fell away when the battery was disconnected. Electron flow through
a conductor then, causes a magnetic field. When the points close, electron flow
causes a magnetic field to be created around the primary. This field also
envelopes the secondary. The points now open, break the circuit and collapse the
field through the primary. The field caving in on itself is movement just like the
rotating magnetic field of the flywheel. This movement is at speeds much greater
than the flywheel could spin - near the speed of light. The rapidly collapsing
field tears through the secondary winding which has sixty turns of wire for every
one turn of the primary - effectively generating 60 times the voltage created in
the primary. The sum total of this is that the secondary winding can create up to
25,000 volts in some systems, which is used to jump the air gap of the spark plug
and ignite the fuel/air mixture in the combustion chamber.
Now for the black box. Magnetron™ solid state ignition systems, in essence, replace
the mechanical breaker points with a transistor. That is, we replace a mechanical
switch with an electronic one. No moving parts, no arcing, no adjustments and
solid state reliability.
Now that we've got an idea of how it all works, let's look at the meat and potatoes
of what is required to create a good spark.
Flywheel:
The flywheel magnet must generate a sufficient magnetic field to start the chain of
events in motion. A fair test is to hold the flywheel on edge with the magnet
facing up. Place the blade of a 10" #3 (1/4") straight blade screwdriver against
the magnet. Release the screwdriver. The magnet should have enough strength to
hold the screwdriver straight out. If we pass this test, assume the magnet is OK.
Rotational speed:
Remember speed is a factor. The engine must be pulled over at a minimum speed of
250 RPM* before the coil will even think about firing. Thick oil on a winter day or
a heavy parasitic load may cause problems. Customers come into play here as well.
Shorter or elderly individuals may not have the leverage or strength required to
reach the RPM required to activate the Magnetron's electronics. *NOTE: Briggs
service manual has it at 350 rpm minimum.
Spark Plug:
The spark plug is a major element of the equation. A new spark plug may require
around 10,000 volts to jump a .030" gap when the engine is cold. This drops to
just 4,000 when the engine is hot as electrons are more easily emitted from a hot
surface. That's one of the reasons the old vacuum tubes in radios had to warm up
before the radio would work. Electrons are also more easily emitted from a sharp
edge than a round one. A spark plug begins to require more and more voltage as the
edge of the center electrode becomes less defined. And finally, an internal short
or carbon/oil fouled plug simply shunts the high voltage burst straight to ground
with no or insufficient spark. NOTE: It only takes 1,000 volts to jump a 0.025” air
gap in open atmosphere, it takes 10,000 volts to jump the same gap at 120 psi,
therefore an open air spark test in not valid.
(Can't get this through some the thick skulls out there).
NOTE: The spark should be a minimum of 10 Kv (10,000 volts) at pull over speed.
Ignition Coil:
The ignition coil is probably the easiest thing to check and therefore the first
thing to check when embarking upon ignition system troubleshooting. Install the
19368 spark tester between the high-tension lead and a good engine ground. Spin
the engine over (at least 250 RPM) and watch for spark in the tester window. As
simple as it seems, this is a fairly comprehensive test. The tester electrode gap
is .166" wide. Those wise in the way of electrons have calculated that it takes
around 13,000 volts to jump this gap. We need 10,000 to jump the gap on a cold
spark plug. Add it all up and we have voltage to spare. As coil temperature can
aggravate minor coil imperfections that normally wouldn't be a factor, the same
test can be done on a warm engine. Engine quits while running? Hook the tester up
in line with the spark plug and start the engine. When the engine quits, monitor
the window. If spark is present, the problem is not in your ignition coil. By the
way, this test stresses the coil well beyond the demand it would see in operation.
Think about it. We're asking the coil to build enough voltage to jump TWO gaps -
the tester as well as the plug. If your engine starts and runs OK cold and hot,
you've got a healthy ignition coil.
One additional test you can perform. Check the impedance (resistance) of the
secondary circuit at room temperature. Hook an ohmmeter test lead to the spark
plug terminal of the high-tension lead and another to the lamination stack
(ground). Your resistance reading should range between 2,500 and 5,000 ohms. If
infinite (no continuity), an internal open circuit exists. Replace the coil. If
infinite and the engine runs, your problem is an internal break of the high tension
lead, a poor attachment of the spark plug terminal or improper mating of the high
tension lead to the coil. A pin within the coil body skewers the lead. If the pin
does not contact the wire core, there will be no continuity. The coil will often
have enough available voltage to jump the gap, so you see spark. The internal
arcing that occurs within the high-tension lead will eventually create enough
resistance that ignition system performance will suffer. If your resistance
reading is much lower than 2,500 ohms, an internal short exists. Replace the coil.
Now, how about some of those old wives tales that just aren't true.
Rust on the flywheel magnets causes a loss of spark. Not true. A magnetic
field does not care about rust. It has no effect on it. Just can cause clearance problems like binding.
A bright blue spark is best. A yellow/orange spark signifies weak ignition.
Not true. Spark color determines virtually nothing. The hottest spark is
ultraviolet which we can't see. Blue spark is cold in comparison to ultra-violet.
Orange and yellow come from particles of sodium in the air ionizing in the high
energy of the spark gap.
Laying the spark plug against the block and pulling the engine over can
adequately test ignition coil output. Not true. The ignition coil will only
generate enough output to jump the gap of the plug. When under compression, the
plug requires twice the voltage to fire. This check is not an accurate test of the
coil and can be misleading.
An armature air gap that is too wide will prevent spark. Not true. Well, sort
of not true. Briggs & Stratton air gaps cannot be made too wide to prevent spark
providing the coil is healthy and the engine is spun over fast enough. A wide air
gap, say .030" will ever so slightly retard the ignition timing as the magnetic
field takes longer to build within the coil windings.
Ignition coils, particularly Magnetron™ coils, rarely fail. If one is suspect,
perform the outlined checks exactly as mentioned. MOST IMPORTANT: Be sure to
isolate the coil from the equipment wiring harness as well as the engine's wiring
harness. That's right, unhook the ignition grounding lead from the coil itself and
use the spark tester. Many a technician is fooled into replacing a good coil
because the coil grounding lead was shorting out against a piece of sheet metal.
DO NOT attach the tester to the spark plug for this test. The engine may start.
Without the grounding lead installed, you won't be able to turn it off. If the coil
is properly grounded to the engine block, engine speed is at least 250 RPM and the
flywheel magnets are OK, there should be spark present in the window of the tester.
If not, repeat the test double checking your procedure. Still no spark? Then and
only then, replace the coil.
A final bit of trivia - All Magnetron™ Ignition coils have the manufacturing date
code cast into the coil body. The coil manufacturing date will usually be within a
month of the engine's date code. That's an easy way for you to tell if the coil
has been changed before. We use this information to match returned parts to the
engine noted on a warranty claim as well as for internal tracking.
- Joined
- Feb 19, 2020
- Threads
- 77
- Messages
- 10,228
The configuration of new Magnetron coil may look like they removed the triggering device but in fact
it is just a redesign.
Now to answer your question what is inside the coil.
1 ea 13mm x 34.5mm single sided circuit board.
5 ea SMD transistors.
8 ea SMD resistors, inductors, and/or capacitors.
(SMDs were destroyed upon board removal so actually identification wasn’t possible.)
1 ea D13003 transistor.
Primary Winding reading is 1.5 - 1.7 Ω.
Secondary Winding reading is about 6 KΩ +- several hundred ohms.
The kill terminal is directly connected to the non-ground side of the primary; hence, explains why you
or anyone else can NOT test the primary trigger circuit. Otherwords this means you can not test to find
out if a Magnetron coil is good or not without installing it in most cases unless you have a specialized
coil tester.
The D13003 emitter is connected to non-grounded side of the coil’s primary via two SMD resistors in
parallel with total resistance value of 1.0 Ω. (One these SMD resistors marked with the 1R0 code for a
1.0 Ω resistor was ½ watt size.) The collector is connected the coil’s primary winding that is grounded.
The base is connected to the rest of the trigger circuitry.
The coil’s transformer turns ratio is approximately 1 to 18 with secondary closest to the core.
In theory if the output D13003 transistor should short the collector-emitter junction and the coil’s
primary winding is still good the ohms reading will drop to 0.5 Ω - 0.7 Ω. If the coil’s primary winding
should short then the ohms reading should be near zero. If the coil’s primary winding should open then
the reading will be well above 1.7 Ω. Applying any voltage to the kill terminal would result in either
coil’s primary winding shorting or opening due to high current experienced. Applying voltage also can
short out the electronics thus making the coil useless. It is also expected that a cold solder joint
connecting the external kill terminal to circuit board would lead to a non kill operation.
Also the high tension lead can be replaced if you wish to fight the glue considering the price of
aftermarket versions of this coil.
This info was acquired through the destruction of the new OEM version of this coil. It also explains the
configuration differences as they have gone to SMD trigger version.
Now for those that wondering why we put diodes in the kill circuit of the dual coil models it because of
the feedback loop created causing one coil to kill the other. This explains why they are destroyed when
12V is applied as these is no built-in reverse bias protection. Now with this in mind you might think
Kohler and Kawasaki coils would be the same wiring. Not so as these diodes are incorporated into coil itself thus
preventing many of the problems that the Briggs have because they don’t incorporate these diodes
it is just a redesign.
Now to answer your question what is inside the coil.
1 ea 13mm x 34.5mm single sided circuit board.
5 ea SMD transistors.
8 ea SMD resistors, inductors, and/or capacitors.
(SMDs were destroyed upon board removal so actually identification wasn’t possible.)
1 ea D13003 transistor.
Primary Winding reading is 1.5 - 1.7 Ω.
Secondary Winding reading is about 6 KΩ +- several hundred ohms.
The kill terminal is directly connected to the non-ground side of the primary; hence, explains why you
or anyone else can NOT test the primary trigger circuit. Otherwords this means you can not test to find
out if a Magnetron coil is good or not without installing it in most cases unless you have a specialized
coil tester.
The D13003 emitter is connected to non-grounded side of the coil’s primary via two SMD resistors in
parallel with total resistance value of 1.0 Ω. (One these SMD resistors marked with the 1R0 code for a
1.0 Ω resistor was ½ watt size.) The collector is connected the coil’s primary winding that is grounded.
The base is connected to the rest of the trigger circuitry.
The coil’s transformer turns ratio is approximately 1 to 18 with secondary closest to the core.
In theory if the output D13003 transistor should short the collector-emitter junction and the coil’s
primary winding is still good the ohms reading will drop to 0.5 Ω - 0.7 Ω. If the coil’s primary winding
should short then the ohms reading should be near zero. If the coil’s primary winding should open then
the reading will be well above 1.7 Ω. Applying any voltage to the kill terminal would result in either
coil’s primary winding shorting or opening due to high current experienced. Applying voltage also can
short out the electronics thus making the coil useless. It is also expected that a cold solder joint
connecting the external kill terminal to circuit board would lead to a non kill operation.
Also the high tension lead can be replaced if you wish to fight the glue considering the price of
aftermarket versions of this coil.
This info was acquired through the destruction of the new OEM version of this coil. It also explains the
configuration differences as they have gone to SMD trigger version.
Now for those that wondering why we put diodes in the kill circuit of the dual coil models it because of
the feedback loop created causing one coil to kill the other. This explains why they are destroyed when
12V is applied as these is no built-in reverse bias protection. Now with this in mind you might think
Kohler and Kawasaki coils would be the same wiring. Not so as these diodes are incorporated into coil itself thus
preventing many of the problems that the Briggs have because they don’t incorporate these diodes
Yes I did set the gap at 0.010. its runs great at my age 77. I am starting to learn more. I did pull the shroud a few times since I bought it and it works great now from the help I am getting here.I have neglected some what . i also did one other thing to my engine I put lock nuts to stop it from vibrating.I am new here