wtbuck12 wrote:

You say it's a "mud" boat can we assume the engine works hard at high
revs & power???

Do you still have a failed coil??? how have the coils failed?? Primary
open circuit?? leaks to case (ground)?? High internal resistance??? Any
cracks or physical signs ??

If it "appears" fine with a multimeter & has no outward signs, then
open it up (it's junk anyway yes??) & have a look for signs of a
breakdown in the secondary windings, the backfire on dying might be a
good clue that high resistance & heat buildup has caused a high voltage
leak which kills the coil at the same time.

If you see such signs of over heating inside, shorts or open circuit
when hot then maybe consider;

Position on the engine; does it get overly hot near a manifold exhaust
EGR heat path?? or an exhaust manifold??

Are the plugs, all leads (incl coil lead) cap, rotor etc all OK with a
standard plug gap?? Some people like larger than usual plug gap. However
anything that offers resistance (which should show on a multimeter or
much better an engine analyser, will even tell you which lead or plug is
to blame:-)) can firstly make the coil run hotter & if the resistance is
too high the coil's internal insulation can fail. i.e. never run engine
with lead disconnected the spark will try to escape anywhere it can,
including inside the coil itself. So make sure the rest of the system is
up to snuff.

You say the dist. "pickup" has been replaced?? but is the low voltage
switching system correct for the coil(s), most are expecting a capacitor
discharge type of primary supply (no dwell) but if you have an old
system it's worth investigating if the type of primary supplied is OK
for the coil, assuming the pickup does nothing more than what an old set
of points/condenser did.

Getting desperate now:-) Sorry.


K


Dave Hall wrote:

On 19 Dec 2004 19:24:09 -0800, wrote:


I have an early 1980's modle 318 Chrysler engine installed in a
mudboat. About 2 years ago I developed a problem with the Ignition
coil burning up. The engine has the original electronic ignition
system installed, but has been completely rewired by a Dodge
dealership, the control module, ballast resistor, and the

distributor

pick-up assy. have been replaced. However, I continue to have the
problem. The engine runs perfectly for about 3 months and then

without

any warning, will backfire and die. There will be no ignition fire
until the coil is replace, then the engine will start up and run

fine

for another few months. Any help or suggestions with this problem

would

be GREATLY appreciated.


Sounds to me like your coil is being "fried" because there is too

much

voltage being run through it. Most coils are designed to run at the
full 12V when starting, but then switch in a dropping resistor which
drops the voltage down to about 8V when running. If this dropping
resistor is absent, the coil will get the full charge at all times.

Another thing to check is your charging voltage. If your alternator
regulator is acting up, and the charge voltage runs up to 16 or 17 V
the same thing could happen. Although, you'd probably notice your
batteries boiling over and very bright lights as well.

Dave


I appreciate all the responses very much. The resistor resistance is
app. 1.2 ohms and running voltage is 8.2 volts. Alternator output is
14.4 volts. The coil is mounted directly to the block and the bracket
seems to be tight and clean, no signs of corrision. I tried install a
higher resistance resistor and dropped the running voltage to 7 volts,
but that made the ign. fire too weak. I have tried using Mopar coils
as well as aftermarket coils with no noticeable differance. Someone
suggested using a HEAVY DUTY coil, where can I buy one and what do I
ask for? This problem certainly has myself, the Dodge dealership and
several local independent mechanics scratching our heads.
Thanks again
Ronnie

On 20 Dec 2004 16:52:07 -0800, "wtbuck12"
wrote:


Dave Hall wrote:
On 19 Dec 2004 19:24:09 -0800, wrote:

I have an early 1980's modle 318 Chrysler engine installed in a
mudboat. About 2 years ago I developed a problem with the Ignition
coil burning up. The engine has the original electronic ignition
system installed, but has been completely rewired by a Dodge
dealership, the control module, ballast resistor, and the
distributor
pick-up assy. have been replaced. However, I continue to have the
problem. The engine runs perfectly for about 3 months and then
without
any warning, will backfire and die. There will be no ignition fire
until the coil is replace, then the engine will start up and run
fine
for another few months. Any help or suggestions with this problem
would
be GREATLY appreciated.


Sounds to me like your coil is being "fried" because there is too
much
voltage being run through it. Most coils are designed to run at the
full 12V when starting, but then switch in a dropping resistor which
drops the voltage down to about 8V when running. If this dropping
resistor is absent, the coil will get the full charge at all times.

Another thing to check is your charging voltage. If your alternator
regulator is acting up, and the charge voltage runs up to 16 or 17 V
the same thing could happen. Although, you'd probably notice your
batteries boiling over and very bright lights as well.

Dave

I appreciate all the responses very much. The resistor resistance is
app. 1.2 ohms and running voltage is 8.2 volts. Alternator output is
14.4 volts. The coil is mounted directly to the block and the bracket
seems to be tight and clean, no signs of corrision. I tried install a
higher resistance resistor and dropped the running voltage to 7 volts,
but that made the ign. fire too weak. I have tried using Mopar coils
as well as aftermarket coils with no noticeable differance. Someone
suggested using a HEAVY DUTY coil, where can I buy one and what do I
ask for? This problem certainly has myself, the Dodge dealership and
several local independent mechanics scratching our heads.

Well, Sherlock Holmes once said something along the lines that when
you eliminate the obvious, what's left, no matter how improbable, must
be the answer.

If your operating voltage is correct, and the coil is mounted properly
and not exposed to the corrosive effects of water then I have to think
that perhaps the shape of the ignition pulse is too sharp.

If there is a sharp spike, which exceeds the operating voltage, over a
period of time, it could cause the insulation in the coil to break
down. The only way to see this is with an oscilloscope. The cure is
simple though, a capacitor from the "cold" side of the coil to ground,
somewhere around .1uF should do it.

Dave

Dave Hall wrote in message
...
On 20 Dec 2004 16:52:07 -0800, "wtbuck12"
wrote:


Dave Hall wrote:
On 19 Dec 2004 19:24:09 -0800, wrote:

I have an early 1980's modle 318 Chrysler engine installed in a
mudboat. About 2 years ago I developed a problem with the Ignition
coil burning up. The engine has the original electronic ignition
system installed, but has been completely rewired by a Dodge
dealership, the control module, ballast resistor, and the
distributor
pick-up assy. have been replaced. However, I continue to have the
problem. The engine runs perfectly for about 3 months and then
without
any warning, will backfire and die. There will be no ignition fire
until the coil is replace, then the engine will start up and run
fine
for another few months. Any help or suggestions with this problem
would
be GREATLY appreciated.


Sounds to me like your coil is being "fried" because there is too
much
voltage being run through it. Most coils are designed to run at the
full 12V when starting, but then switch in a dropping resistor which
drops the voltage down to about 8V when running. If this dropping
resistor is absent, the coil will get the full charge at all times.

Another thing to check is your charging voltage. If your alternator
regulator is acting up, and the charge voltage runs up to 16 or 17 V
the same thing could happen. Although, you'd probably notice your
batteries boiling over and very bright lights as well.

Dave

I appreciate all the responses very much. The resistor resistance is
app. 1.2 ohms and running voltage is 8.2 volts. Alternator output is
14.4 volts. The coil is mounted directly to the block and the bracket
seems to be tight and clean, no signs of corrision. I tried install a
higher resistance resistor and dropped the running voltage to 7 volts,
but that made the ign. fire too weak. I have tried using Mopar coils
as well as aftermarket coils with no noticeable differance. Someone
suggested using a HEAVY DUTY coil, where can I buy one and what do I
ask for? This problem certainly has myself, the Dodge dealership and
several local independent mechanics scratching our heads.

Well, Sherlock Holmes once said something along the lines that when
you eliminate the obvious, what's left, no matter how improbable, must
be the answer.

If your operating voltage is correct, and the coil is mounted properly
and not exposed to the corrosive effects of water then I have to think
that perhaps the shape of the ignition pulse is too sharp.

If there is a sharp spike, which exceeds the operating voltage, over a
period of time, it could cause the insulation in the coil to break
down. The only way to see this is with an oscilloscope. The cure is
simple though, a capacitor from the "cold" side of the coil to ground,
somewhere around .1uF should do it.

Dave

Dave's response rang a dusty old bell in my head. I seem to recall an issue
with electronic ignition systems for cars, particularly when they first came
out and were being retro-fitted to the older points and condenser systems.
Coils were dying a quick death due to the sharper pulse of the electronic
ignition. A higher performance coil was required to cure the problem.

Eisboch

On Tue, 21 Dec 2004 12:16:55 GMT, "Eisboch"
wrote:

~~ snippage ~~

Dave's response rang a dusty old bell in my head. I seem to recall an issue
with electronic ignition systems for cars, particularly when they first came
out and were being retro-fitted to the older points and condenser systems.
Coils were dying a quick death due to the sharper pulse of the electronic
ignition. A higher performance coil was required to cure the problem.

The man is hot today.

Another good point.

Later,

Tom