Coil input information

[Marian Claire]

Had a chance to do some testing on the MC. Here are some of the #s. Battery rested 12.4 vdc, remotely located coil installed spring of 2011 is 3.3 ohms and EI. After a 30 minute run under load the coil + readings, 13.38 @ 900 rpm, 14.07 @ 1600 rpm, 14.2 @ 2000 rpm. All are producing above the 4 amp upper limit. I did not have a way to check coil temp but I can say it was never to hot to keep my hand on it. Very subjective I know.
Other thoughts:
I ran for years on my old coil before it failed this spring. Many hrs at 2000 rpms. No idea what resistance it was. Prier to the spring trip I did some "spaghetti removal" and connection cleaning. Also about 7 days before the failure, the morning my wife flew into Marsh Harbor of course, my old 4 way, off/fan/fan-ign/ign switch died and as I rewired I eliminated the switch and several feet of wire from the ignition wiring.

Any harm in just putting in a 1 ohm resistor? That would easily cover my high, 15 vdc, Edit "estimated" reading but would only provide 2.92 amps at my lower,13.15 vdc, reading with the spare coil that is 3.5 ohms. Dan S/V Marian Claire
Edit: I should point out that I normally cruise at 2000 to 2400 rpms.

[sastanley]

Dan,

I am going to throw my own opinion out on this one, so I'll use Jerry's disclaimer, YMMV! - I think the key to this whole thing is to get the running coil input voltage as low as possible while still giving it just enough with the starter cranking to fire the plugs and start the motor.

I am still having issues here on my boat too, so you may not want to take any of my advice! Engine ran at 1,800 RPM this weekend for well over an hour, took a 15 minute rest while we pumped out the holding tank, and then re-started, ran for one minute, and quit 15 minutes from the slip. New coil would not start it up either...Neil and I have chatted offline and he suspects I've probably fried the Pertronix EI unit now, since I have some visual spark, but not enough to fire the engine I guess.

Yay boats!

[ndutton]

Dan,

Is your coil resistance actually measured or as reported by the manufacturer? We've seen that manufacturer's specifications can be off by as much as 10% or slightly more.

Based on the current information and testing it's my opinion that the addition of a 1 ohm resistor would be prudent. There's some concern with performance at lower RPM but your own testing will tell the tale.

It's my opinion (opinion only) that coils tend to tolerate a little excessive amperage for a while but I think the greater the amperage the shorter the life. This applies to the EI module as well. You're running at 4.3 amps at 2000 RPM or only 7% over the maximum recommended. If you were running at say, 6 amps you'd likely cook the coil and possibly the module in less than an hour. Ask Shawn, I didn't make up the 6 amp example!

Why the big voltage out of the alternator? Are you charging AGM batteries? I can't think of any other reason for a charging voltage that high.

[rrranch]

I just bought my first boat with an inboard engine but I have a LOT of experience with antique tractors and hot rods. I think everyone is overthinking this stuff. Coils were always made for 6 volt systems to the best of my knowledge. 9 volts to allow for generator output. Later adaptations were made to allow them to be used with 12 volt generators and alternators by coming up with external ballast resistors and internal to the coil ballasts reducing the voltage anywhere from 4.5 volts in an old chrysler to almost 8 volts in a chevy. The only time I ever fried a coil is when I converted my last farmall from 6 volt positive ground to 12 volt negative. I completely forgot to hook up the ballast resistor. I always used one meant for a chrysler. Like a 68 dodge duster or something with a 6 cylinder. It was a 4.5 volt ballast. Coils lasted forever on that thing. Sure it was low voltage but so what? Those old slant 6's were not exactly hot rods. On my wifes car, a 73 Buick with a souped up 455 in it and original delco points distributor, I still use an original resistor wire in it. Those allow 7 volts to the coil. Never had a problem with that one either. I'm a little anal about keeping the points properly dressed on that one and keeping the drwell set perfectly. I have a big old antique sun machine in my shop that does that nicely. On the farmall, I file the points once a year if that and set the gap. I usually replace the ballast too because it is exposed to the weather but even when I have a dead battery on that thing and use the hand crank it popps off on the very first turn every time.

I have learned that external ballasts get wet and break. They run kinda hot while doing their job. They must be prone to corrosion too on a boat. Just guessing. That will change the resistance for sure. Another thing I have learned is that plug wires make a lot of difference. Industrial engines, tractor engines and most others like ours never used these silicone supression type wires. I tried a set of those once on the farmall and they just absolutely sucked. The only reason for them is to reduce radio interference on an old amjam radio. You shouldn't hear it on a FM band or VHF. Solid core tractor wires definitely rule. They last forever and allow every bit of the current from the coil through to the plugs almost. Much more than silicone ones would. In watching the o scope on my sun machine it makes a huge difference in the dwell angle and when the field collapses on the coil too. It's a much cleaner straighter line. I always run solid wires.
As for burning coils though. The only thing that will do it is pretty much too much juice. Just run a chrysler ballast and change it when you do the plugs. That's what I plan to do. Mine has electronic ignition in it now but I am converting it back to original just to keep it simple.

[sastanley]

Dan,

It's my opinion (opinion only) that coils tend to tolerate a little excessive amperage for a while but I think the greater the amperage the shorter the life. This applies to the EI module as well. You're running at 4.3 amps at 2000 RPM or only 7% over the maximum recommended. If you were running at say, 6 amps you'd likely cook the coil and possibly the module in less than an hour. Ask Shawn, I didn't make up the 6 amp example!

Neil, since we've brought it up, can you help the electrically challenged folks like me and explain how you arrived at 6.51 amps? (if I remember correctly) based on the info I provided??

If I remember it, here is what I had on Sunday:
12.9 volts @ bus bar
2.2 ohm resistor in line
9.77 volts at 1.5 ohm internally resisted coil (+) terminal while running.

[Marian Claire]

Thanks guys. Will try and answer but this is not my strong suite. I measured the coil resistance for both coils. I have the old prestolite ALE 5204?? alternator. It has a external regulator vbv 6201 I believe. I get 13.8v+- at the battery during charging. The reading at the alt out generally ran .5 v higher than the coil +. I did not check the voltage out of the voltage regulator at the ignition connection. Its a PITA to get to. The 15vdc # was not actually observed. I based it on: The highest I actually saw at coil + was 14.85 @ 1600 rpm under load at the very beginning of the last "warm" load test. I did not get a 2000 rpm #. I also had a alt out reading of 15.5 at the very first start up but could not get a solid reading at coil +. Clear as mud right. Dan S/V Marian Claire

[thatch]

"Not so fast"

rrranch,
You no doubt have had considerable experience with different types of ignition systems on many different engines. What we are dealing with here is a group of guys who are trying to update and assemble a dependable, low maintainance ignition system that will perform well. If some in the group want to stay with a points system and deal with the mandatory maintainance involved, that's up to them, I personally would rather not. In building an updated "electronic" system, one of the things that has proven to be a definate "no no" is the addition of solid core spark plug wires. Aside from the obvious radio interferrence, the decreased resistance of these wires places an excess load on the ignition control module. After chasing a habitual shutdown problem years ago in my hot rod, the Pertronix engineers finally ask the question "are you running soild core wires?". The replacement of those low resistance wires cured the problem.
Tom

[rrranch]

I never thought about that with electronic ignition. Good point and thanks for correcting me.
Although, there is one bad thing about electronic ignition in my opinion. They either work or they don't work. It's an expensive spare part to carry and I learned with my 69 mustang to carry a spare. I had a mallory unilight system on it and it fried 2 or 3 times I think. The first one was out by Barstow California before there was anything in Barstowe! That sucked.
With points, a spare condensor and a point file ( maybe a can of WD40 in case they get wet also) is all you really need to carry. They are super easy and reliable systems but maybe just because it's such old tech people often misunderstand them and are afraid of them. I love points.

It's kinda like the difference between my wifes old Eddison hand crank record player and the new TV that got hit by lightening. We've been listening to the Eddison a lot lately. haha.

[ndutton]

ranch,

I'd say you're not a candidate for EI and there's no shame in that. Points systems have worked fine for 70 or 80 years in engines in general and decades in A-4's too.

I wanted to respond to a couple of your comments though:

Although, there is one bad thing about electronic ignition in my opinion. They either work or they don't work. It's an expensive spare part to carry and I learned with my 69 mustang to carry a spare.

Virtually all of us with EI keep our old points/condenser still mounted on the distributor plate (EI comes with a new plate) and pre-adjusted for gap/dwell. In the event of EI failure it's easily installed and costs nothing to carry, we already owned it in the first place.

. . . . maybe a can of WD40 in case they [the points] get wet also . . . .

WD-40 is highly flammable (excellent diesel starting fluid) so in the presence of a breaker points spark you'll likely have a little poof under the distributor. cap.

[ndutton]

Neil, since we've brought it up, can you help the electrically challenged folks like me and explain how you arrived at 6.51 amps? (if I remember correctly) based on the info I provided??
If I remember it, here is what I had on Sunday:
12.9 volts @ bus bar
2.2 ohm resistor in line
9.77 volts at 1.5 ohm internally resisted coil (+) terminal while running.

Here's how I saw things Shawn:
Regardless of what's going on ahead of the coil (alternator, buss bar, resistor, whatever), at the coil you're reading 9.77 volts. The other end of the coil's primary winding (the - post) goes to a switched ground through the electronic ignition module (in ranch's case it would be the points) to complete the circuit. So following Ohm's law, V=IR (Volts = current x resistance). Algebraically manipulated, I=V/R or Current = 9.77 volts (at the coil) divided by 1.5 ohms (coil resistance).

9.77/1.5= 6.51 amps or over 150% of Pertronix's recommendation.

That amperage not only flows through the coil but also the EI module through which the system gets its ground path. Hence, my off-list conclusions we discussed, aka the double-poof opinion. I'm not sure which died first, the coil or the module but regardless, your engine would not restart and you know me well enough by now, CHANGE IT ALL!!

Now I'm not suggesting there aren't other ignition systems working fine with a variety of voltages and coil resistances. In this thread my goal has been to follow Pertronix's advisement of a 4 amp maximum system amperage with their Ignitor electronic ignition and to monitor the effect the lower amperage had on coil temperature, a known factor in coil failure. My suggestions earlier built in an additional safety factor in consideration of the 4 amp number being a maximum.

I believe we also discussed the option of installing the old points system with your brand new 3 ohm coil in the interim.

[rrranch]

I wish I had another plate with points. My boat came with electronic ignition. Looking for another whole distributor now to rebuild and keep on hand.
I never saw or heard of WD40 catching fire but I guess it can happen. I personally hate the stuff but I do keep a can around for my wifes car. I used to use cases of it at work getting tractors started by spraying under the dist cap and on the points. It sure got the water out.

Does it say on the ignition module anywhere what brand they are in case I wanted to order another one like I have? I haven't pulled the cap yet to look at it? I was guessing these distributors have the oil wick in the top of the shaft for the bushing. I planned to oil that this week and check it out.

[sastanley]

Neil, thanks for those details.

I might as well put out all of the laundry to help others related to today's events.

I managed to get the boat back to her slip this afternoon under her own power...no tow boats, or sailing into the dock required after she sat at the local sailing club's dock since Sunday afternoon.

I changed out the Pertronix 1146a EI with my (new) spare unit. I also put the 0.8ohm resistor in front of the (also new) Pertronix 3.0 ohm coil.

After much cranking and fiddling with the EI unit magnet's (finicky) placement on the distributor shaft, and a few rags full of gas out of the carb/flame arrestor area & finally blowing out all the crud/raw gas, etc. that was in the motor...she started and ran. Much to my surprise, I was seeing 15.78volts at the alternator post and 14.xx at the coil (+) post. When it rains it pours!

I am possibly deducing now that the regulator on the alternator failed, and for some point in time, I was frying everything with excessive voltage when the engine last ran this past weekend...although I did not see any excessive voltage on the volt meter in the cockpit during that time. But, when the motor is running well and you are busy looking at oncoming boats in a busy harbor...who's staring at the gauges??

After the above readings at the safe haven of the club's dock, but realizing I needed to get the boat home to her berth soon, I pulled the alternator belt and ran just off the battery (a trick I learned from Dave Neptune!). The engine ran great for 35 minutes at 1,850 RPM with ~11 volts on the instrument panel gauge in the cockpit to the dock. I had another fully charged battery (starting battery) ready if I needed to switch over, but I suspect the 90Ah house battery would have powered the motor for probably an hour more or two if necessary, as the battery itself (via volt meter reading in the slip) was still about 12.4v.

I obviously have some other issues to deal with. I know what you are saying already, Neil...lose that silly adjustable regulator and get something fixed at the right voltage...trust me..I am listening. I may be calling Ken for the proven 55A alternator in a few days.

(edit - This issue turned out to be a bad voltmeter, but it was a fun experiment to run the engine without the alternator.)

[ndutton]

I know what you are saying already, Neil...lose that silly adjustable regulator and get something fixed at the right voltage

Sheez Shawn, do I nag that much??

Truly though, great information. Your voltage measurements were timely and point you on a path of resolution. You have issues but it looks like you have them surrounded. I wonder how long the high voltage existed.

ranch,
The two common electronic ignition systems found on A-4's are the Pertronix 1146A (magnetic pickup) and the Indigo optical trigger system. In this thread we've been working with the Pertronix. I think the unit Moyer sells is a Pertronix. There's a third one out there, the Hot-Spark 3DEL4U1. I've never heard of anyone around here with a Hot-Spark.

And is my way, here's a bit of useless trivia - the 'WD' in WD-40 stands for 'Water Displacement.'

[hanleyclifford]

Shawn - Before you convict and execute the regulator I have a question: where are you sensing with your regulator? It must not be at coil + or anyplace where the voltage is being reduced with a resistor (or anything else for that matter). The best place to sense is at batt common or on the main buss bar if so equipped. There is always a danger of "fooling" a regulator into calling for more output from the alternator than is really wanted. Of course the sensing circuit must be switched (with an OPS) and fused.

[roadnsky]

Sheez Shawn, do I nag that much??

Nag, nag, nag!

And is my way, here's a bit of useless trivia - the 'WD' in WD-40 stands for 'Water Displacement.'

...and the '40' is the 40th version of the formula