Some comments about coils
 

There’s a technical matter that deserves our attention. Our faithful Web Shepherd is constantly looking behind every digital rock in cyberspace, to warn us of any “wolves” that might be threatening our flock from the outside. Currently, he’s frantically waving a red flag about reports of premature coil failures in the immediate aftermath of installing an electronic ignition kit. To be fair, I should point out that he has been waving this particular flag at least once or twice each year for the past several years, so the subject clearly deserves a closer look.

BACKGROUND:

Electronic ignition systems (by design) provide a slightly higher dwell time within the primary circuit, which means that coils will normally operate at a somewhat higher temperature in an electronic system than they would in a comparable conventional system.

Technical representatives from Pertronix (the manufacturer of the Ignitor) continue to tell us that any good quality automotive oil-filled coil, with at least 3 ohms resistance in its primary windings, will work well with their Ignitor in our Atomic 4 application. There also seems to be agreement among other experts with whom we network that oil filled coils are somewhat more efficient in terms of dissipating the additional heat created in electronic systems than are solid epoxy coils (which is no doubt why oil filled coils typically feel hotter to the touch).

Epoxy filled coils are reported to have an advantage where high vibration is anticipated, or where a coil is to be mounted in any position other than upright. Oil filled coils apparently have somewhat of a tendency to leak oil from the bottom of their high tension post in any orientation other than upright. Solid epoxy coils are also somewhat more resistant to mechanical damage and the effects of corrosion in a marine environment.

Our own experience tends to support all of the foregoing rationale. Our experience also suggests that heat buildup is the most tangible threat to coil life, so the coils that we have been using and marketing for over 8 years are metal-jacketed oil-filled coils with 4 ohms of resistance within the primary circuit. They have been extremely reliable, in both conventional and electronic ignition systems, with a failure rate so low as to never have made it to our radar screen of concern.

A CLOSER LOOK:

In more recent conversations with the folks from Pertronix, we have gleaned the following information:

If your coil appears to be an original unit (perhaps 30 or more years old), has noticeable rust on the outside of the metal jacket, signs of mechanical damage or any indication that oil has leaked out of the metal jacket, it’s definitely wise to replace the coil. Realistically, it would be a good idea to replace such a coil, even if one were not installing an Ignitor.

Pertronix also recommends (as a matter of Ignitor reliability) that the current flowing within the primary ignition circuit should not exceed 4 amps. You can determine the current within your primary circuit as follows:

1) Measure the ohms of resistance across the primary terminals of your coil (with all leads disconnected).

2) Reconnect the coil leads, and ground the negative terminal of the coil with a wire of approximately 14 gauge. With the negative terminal of the coil grounded and the ignition switch on, read the voltage at the positive terminal of the coil.

3) Calculate the amperage within the primary circuit by dividing the voltage measured at the positive terminal of the coil by the resistance measured across the primary terminals of the coil. Example: 12 volts (as measured at the positive terminal of the coil) divided by 3 (the normal resistance measured across the primary terminals of a coil) = a maximum primary ignition circuit current of 4 amps.

NOTE: By comparison, the coils listed in our online catalog (with 4 ohms internal primary resistance) would result in only 3.5 amps within the primary ignition circuit, even if a high output alternator were installed to raise the system voltage to 14 volts.

RECOMMENDATIONS:

1) We have no failure data to suggest that you need to automatically replace your existing coil, as long as it meets the criteria in the above recommendations from Pertronix.

2) If you do decide to replace your coil (for any reason), and vibration and/or concerns over corrosion are not a primary consideration, we continue to believe that a standard good quality, metal-jacketed, oil-filled coil is a very prudent choice.

Best regards,

Don Moyer

Don-

Is there an disadvantage going with the flamethrower epoxy filled coil? I chose it because of vibration, but wonder if this my be contributing to my immediate shutdowns I've mentioned in prior thread.

Thanks.

John

John,

There's no reason to believe that the Flamethrower coil has anything to do with your intermittent shutdowns.

Don

engine electronic trouble
 

I own a 1977 SeaRay SR200. Its powerplant is the original Mercruiser 250 V8. My trouble comes in usually about half way through the season. When I try to pull a skier and really hit the throttle the engine "caughs and sputters" and i get very little power. If i replace the plug wires the problem goes away, but i only get a single season out of a set of wires (i have tried marine wires and automotive wires with the same result) My season is not long either, i usually boat 6 or 7 times a year if i am lucky. I am considering upgrading my engine to electronic ignition, will this take care of my problem? if not, any suggestions as to how to fix my problem?
thanx
busam2004

Your Mercruiser is a far cry from our little four cylinder flat head Atomic 4 sailboat engine, but when an engine coughs and sputters when accelerating, it's usually an indication of a lean fuel mixture or a timing issue. I'm suspicious that your symptoms might come and go somewhat randomly (perhaps more prevalent when the engine temperature was high), and as you replaced your plug leads you picked up the mistaken impression that changing the leads was correcting the problem.

If you have an adjustment for your high speed fuel system, I'd make it a bit richer, and I'd check the timing as well. You may be a bit on the advanced side.

Don Moyer

Coil Swapout
 

My coil was possibly an original 1974 installation. I believe that occasional stoppages were from coil overheating. I ordered an epoxy coil to go with my electronic ignition, from Moyer last year. In swapping out the 7 wires on the coils I possibly put BOTH distributor wires on the plus terminal. This is a No-No according to the installation instructions. I now have no spark. Power gets to the coil all right. Have I destroyed the electronic ignition? How can I check this? May be an expensive lesson.
Regards,

Harley,

You probably did ruin the module in your electronic ignition system. It would be best if we could talk on the phone to be sure. If you did ruin your module, I'll try to come up with a fix for you without replacing your entire system. Our tech service line is (410) 810 - 8920. If you email your phone number to info@moyermarine.com, I'll try to reach you as well to save time.

Don

A Recent Coil Experience
 

Thought you might find this interesting.
When I acquired my C&C 35 this spring (came with an A4) I motor/sailed her from Deale MD to Quebec. I purchased, and had hoped to install, an electronic ignition upgrade before the trip but weather precluded that happening.

We were about 45 minutes underway when the engine sputtered and died. After fiddling for about 30 minutes it restarted. Ran for another 30 minutes or so and died again. At this point I remembered reading about "infant death" syndrone in coils. I installed the coil that came with the upgrade kit and for the rest of the 10 day trip I had no coil problems.

Now it gets interesting. A week after arriving I tried to start the engine and it wouldn't. Finally I swapped the old coil back in and the engine fired up immediately.

This past week I finally installed the electronic ignition upgrade (along with a new water pump and adjustments to the "clutch") and I switched back to the new coil. 45 minutes into the sea trial the engine died. By now I had purchased a new backup coil. Swapped it in and the engine immediately fired up and ran for the next 20 minutes, back to port.

Friends have started to suggest I buy coils by the caseload <grin>
Ken

Ken,

I'm not sure you need more coils. It seems you would only need a pair of
quick disconnects to swap the two you have.

Actually, I'm not at all sure that coils are your problem. I fear that you
may have fallen into the "snapping fingers to keep elephants away" syndrome,
and you're now afraid to stop snapping. Intermittent shutdowns tend to set
one up for this dilemma. When the engine shuts down only intermittently, no
matter what you change, the engine is likely to start back up and give you
the impression that what you changed fixed the problem.

You might try connecting a jumper wire between the positive of the coil and
the big battery cable on the starter solenoid. If your shutdowns cease,
your problem is most likely a loose connection somewhere in the primary
circuit between the big battery cable, the ignition switch, and back to the
positive terminal of the coil.

Important: you cannot leave the jumper wire installed between usage since it
is exactly the same as turning the ignition switch on, which would deplete
the batteries or burn out the coil - whichever occurs first.

Don

no spark
 

This spring I can't get any spark on the Atomic 4 in my '73 Columbia 30. I can hold the end of the wire coming out of the center of the coil, and touch the block firmly with the same hand, while cranking with ignition on, and not feel a thing. I can hold the wire end 3/8 to 1/16 inch from the block and not get a spark.

I've replaced and gapped the points. I've replaced the condenser. I've replaced the coil. The coil I took off read "use with external resistor", the one I put on reads the same thing, but I can't find any external resistor or resistive wire. I've always asked for ignition parts for a mid 60's Chevy II.

A low-voltage tester lamp with the probe on the - side of the coil wavers in intensity, though always on somewhat, while I crank. My cheap multimeter shows 12 volts at the + side of the coil when my ignition switch is on. I measure maybe 5 ohms internal to the both the old and the new coil (between the +/- poles). The ohmmeter doesn't find much resistance if any in the wire between the - pole and the condenser attachment point on the contacts. I get about 60 ohms between the moving and fixed part of my points when they are apart, which surprised me, I figured that would be infinite.

Any ideas?

John,

I'm attaching our troubleshooting guide for absence of spark.

In the meantime, you should either install a 1 to 2 ohm ballast resister in the circuit from the ignition switch and the positive of the coil or replace the coil with an internally resisted coil. Using a coil designed for external resistance without external resistance will reduce its life to little more than a year.

In another matter, I would check your volt/ohmmeter. The resistance between the positive and negative terminals of the coil should read only about 1 1/2 ohms for an externally resisted coil. Even an internally resisted coil only measures approximately 3 1/2 ohms across the primary terminals.

Yet another matter: I recommend connecting your 12 volt test light between the positive and negative terminals of the coil. The lamp will then turn on and off as the points open and close (in parallel with the coil) which makes timing seem more logical; i.e., you place the engine with the first cylinder at the flywheel end of the engine at the top of its power stroke and then slowly rotate the distributor until the test light goes off. This is then also the time that the primary circuit of the coil is energized to create a strong secondary discharge from the center post.

Good luck

Don

Just a reminder to folks:
There's no reason you can't move your coil from the block.

Having it right next to the exhaust and bolted to the engine gives it plenty of heat and vibration, both of which it doesn't like. Buy a longer center wire and move it over to a bulkhead where it will be nice and cool.

How does a coil problem manifest itself?

I recently rebuilt my engine and may have replaced a new coil with a questionable coil that I had saved as a spare (As I recall this coil question occurred just after installing the Ignitor a few years ago!) The engine has been running great until this weekend. It was the first extended trip. I motored Saturday afternoon for about 2 hrs. When we anchored the engine stalled at idle as I was preparing to drop the anchor. I couldn't restart it. I noted a spark from the coil wire and decided it was a fuel problem so I left it for the next morning. However, the next morning she starred right up so I didn't investigate further. After a great sail on Sunday I again motored for a couple of hours back to our mooring to meet friends. Again, as I slowed to an idle and was I was just about to pick up the mooring lines, the engine stalled. Like earlier it could not be restarted.

Now I went right to a fuel condition and took off the fuel line. A crank instantly proved this wrong as fuel gushed out. Incidentally, some gas spilled onto the coil and vaporized. The coil was extremely hot. I again pulled the coil wire and cranked and this time noted that though there was a spark it was anemic and barely jumped a 1/4 inch gap. Suspecting the coil was being effected by the heat I applied a hunk of ice to the coil for a few minutes and cooled it down enough that I could touch it. The engine then started right up.

Does this sound like an coil problem or should I keep looking?

Pertronix also recommends (as a matter of Ignitor reliability) that the current flowing within the primary ignition circuit should not exceed 4 amps. You can determine the current within your primary circuit as follows:

Don, how do you limit the current flowing within the primary circuit to 4amps if it is greater than that?:confused:

It's my understanding that their minimum specification of 3.5 ohms resistance in the primary windings of the coil (as measured between the primary terminals) is designed to insure that the current draw in the primary circuit will not be exceeded. I'm hoping that one of our electrical experts will check in quickly since you're dragging me a bit out of my comfort zone in things electrical with this question (I wasn't even aware of the 4 amp restriction).

Don

to calculate amps the formula is voltage / resistance(ohms) = amps

14.2(output from Alternator) / 3.5 (coil resistance) = 4.05 amps

The Pertronix coil states is has a resistance of 3.0 ohms which would make
the amp draw of 4.7.

The Pertronix Web site does say 4 and 6 cyclinder engines should not exceed
4 amps. I would of thought that if this was the case then they would of designed the coil for a higher resistance instead of adding a ballast resistor.

Smosher - are you saying that the Pertronix coil has a "ballast resistor" that must also be connected to the ignition circuit - or do you mean a ballast resistor must be added to the circuit in the above example in order not to exceed 4.7amps?:confused:

If so, what would a schematic of the circuit look like?:confused:

(I was under the impression a ballast resistor is added to a 12 volt ignition circuit to reduce the current to 6 volts when using a 6 volt coil so as to obtain an adequate spark when starting the motor.)

I have the pertronix coil and it didn't come with a ballast resistor.

I should measure the coil but if the 3.0 ohm coil is actually 3.5 or greater then it would be close enough to 4 amps. I'm kinda literal so when I see 3.0 I assume 3.0.

A ballast resistor would go between the ignition switch and the + side of the coil

Steve

Don, thanks so much for this thread (and all of your other bits of wisdom)- once again, you saved me lots of anguish and expense.
After motoring for about 4-5 hours, my trusty A4 just stopped. Checked the fuel, found some crud in the Racor, installed new filter, drained gas from carb bowl, removed and cleaned jet, restarted, and thought "that was easy".
About 1 hour later, engine quit again. While scratching my head, I recalled this discussion about coil failures and after a bit of observation, satisfied myself that coil overheating was indeed the problem.
One interesting twist that I can't figure out is that with the faulty coil, there was no charging of the batteries by the alternator (found this a bit later when I got a low battery alarm while engine was running) but BOTH problems were fixed when I installed a new coil.
How is charging related to coils? I didn't change or replace any wiring, just hooked existing wires to the new coil.
Thanks again for your invaluable interest and services.

It may be because it's so late in the day, but I can't think of a single explanation for how a coil would be involved in a charging issue. Fortunately there is a lot of electrical expertise now on the Forum that is hopefully even now swooping in to enlighten us.

Don

Don, I managed to leave my ignition switch on for several days...yep, I am definately getting older!

I returned to the boat and after discovering I left the switch "on" (my on- board charger kept the batteries charged) attempted to start the motor. Normally it started on the first turn of the engine but after 3 tries concluded I must have damaged either the ignition module and/or the Pertronix Flame Thrower coil.

I replaced the ignition module as routine and then checked for spark - it appears orange couloured and weak and the motor still won't start. Fuel is flowing to the carb and I am getting a nice fuel vapor from the plug holes if I rotate the motor with the fuel tap on. (Something I don't do for long after having a similar experience with my 1975 Norton Commando where I started a beautiful fire at the plug hole whilst testing for a spark!)

Any thoughts on whether it is time for a new coil?:o

PS - I think my description as a "senior member" particularly appropriate at this time!

While awaiting Don's reply, maybe I can chime in with a couple of thoughts. Might be a good idea to check the whole primary ignitiion circuit, to make sure no other electrical components overheated leading to poor electrical conduction. When we bought this boat and had it checked by a mechanic, the first thing he said was to install a high engine temp/low oil pressure alarm. It buzzes incessantly if the ignition key is left on. I got this one from MMI and it has been working great: http://www.moyermarine.com/cgi-bin/s...ey=KTAS_01_191.

I have the same alarm system as Rigsy with one additional component, a delay-on-make relay. Once the ignition is turned on, the alarm system doesn't arm until 10 seconds later allowing me to start the engine without any initial alarm noise. Here's where I found it:

http://www.mcmaster.com/#77055k63/=3pobtk

Ccorv,

Whenever an ignition switch is left in the "ON" position a three-way struggle takes place between the battery(s), the coil, and the electronic ignition module. If the electronic module fails first, the coil and batteries might be saved. If the electronic module (or for that matter the points and condenser) hangs on, a good coil will normally win over the batteries and continue working till the batteries are gone.

Unfortunately, with shore power connected, the batteries hold a big trump card so the coil and electronic module are left to fight it out among themselves. In your case, it does appear that the electronic module hung on long enough to do serious damage to the coil through over-heating.

To build on rigspelt's point a bit, whenever an ignition switch is left in the "ON" position, the "soldering iron" concept sets up the possibility that the primary circuit itself can heat up over time and create damage to wiring below the current flow required to blow a protective fuse - even if a proper 20 amp fuse is installed in the circuit.

Don

NDUTTON,
Thanks for the info on the relay. I am curious though as to how you wired it into the circuit. When I got "Solution" it would not start. Instead of an ignition switch and starter button, she has a regular momentary on type ignition switch and as a result, a small car type relay wired into the circuit. I was able to diagnose that the relay was bad and hot wired it. Even though I was able to find a generic replacement from NAPPA, I carry a little remote starter switch for when the new relay corrodes.
Do you have your timer relay wired the same way? In other words, is the timer relay suitable to serve as a starter relay as well as an alarm?

Mark
Cat 27, "Solution"