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