Coil issue? Runs for 90 minutes and quits

[pdecker]

After having intermittent engine problems for a year in which I replaced the wiring harness, instrument panel, carburetor, fuel filter/water separator, and installed electronic ignition, I was still having some hard starting, rough running problems with my late model A-4. I finally replaced the Flamethrower coil that still has 3.0 ohms resistance with a new Moyer coil that has 3.8 ohms resistance. Now it starts easy and runs smoothly! But only for 90 minutes. The engine shuts down suddenly and will not re-start until the next day. The coil is screaming hot when it shuts down. I have a total of about five hours of running time on the coil, since I've done some shorter trips.

I now know that my electronic ignition (EI) wants 4.0 amps max, and the 3.0 ohm coil, it was possibly getting 4.9 amps since the the open circuit output of the alternator was measured at 14.7 V. I have not measured the voltage output at the coil with power on yet. I have removed the alternator and will have it bench tested tomorrow since I haven't done that in many years.

Is my new coil or my EI toast? Could something besides the alternator be causing the coil to get so hot? Should I try an external ballast resistor?

Phil Decker
S/V Catmandu
1982 Catalina 27

[Dave Neptune]

Phil, if you have no spark when it dies it is the coil probably. Get a coil and do not hook it up without a RESISTOR!!!! At 14.7 you will fry many a coil!!

Dave Neptune

[hanleyclifford]

You should get a voltmeter on coil + and if it reads more than 12 volts with the engine running shut it down and put in another resistor until you get below 12 volts.

[ndutton]

Well, as expected I disagree

The root problem is your alternator output is too high (should be more like 14.0 to 14.2 volts) and heaping on resistance to compensate for it protects only the coil, not everything else like pumps, lights, electronics, etc. Why not fix the problem instead of masking it with a work-around?

Regulator replacement (if fixed) or adjustment (if adjustable) down to the values mentioned above will make your batteries happier, they'll probably last longer, your other 12V equipment on board will be happier and you won't need ANY supplemental resistor for your engine with a new Moyer coil. You need a new coil, this one is toast but as Dave said, replacing it without dealing with the voltage (via supplemental resistance or regulation or a hybrid of the two) will destroy the replacement as well.

[joe_db]

14.7 will have you replacing batteries AND coils.

[pdecker]

Just had the alternator bench tested

I just took the alternator to the shop, and Nick, the guy with 35 years experience said it was good. It went up to 14.0 to 14.1 V nicely. Perhaps I measured wrong before when I saw 14.8. But he said it might be a regulator problem and that my alternator is externally regulated. I disagreed, and said the regular is on the back of the alternator, and my alternator looks just like all the Motorola 35A alternators in the manuals. The alternator Aux output is always wired directly to the coil + side, and there is no regulator in between. Nick would not hear it, but I think Nick is wrong.

What would it do differently if I had a bad regulator? Should I take it to another shop since the alternator is out anyway?

[ndutton]

Technically you're both right Phil. Based on your description (just like the Motorola) the regulator is mounted on the back of the alternator body and serves as a sealed lid for an ignition proof chamber for the spark producing components.

Nick is looking at the regulator in electrical terms. It is not integral to the alternator, connects with external wires. It could just as well be mounted on a bulkhead and connected with longer wires and work just as well with the exception of compromising the ignition proof integrity.

Back to your problem, you need to determine beyond question the output voltage before deciding on a remedy. BTW, we have reports of Motorola regs drifting their voltage up on their own. It's time to get a real measurement. Also, an alternator with 15V output may work fine on a Crown Vic police cruiser but such an application does not have a current limited Pertronix 1146A electronic ignition. There are considerations in our application of which Nick may not be aware as he pronounces the alternator healthy.

[joe_db]

Also note some people use aftermarket regulators on the Motorola and leave the stock reg in place as a spark shield, me included

Technically you're both right Phil. Based on your description (just like the Motorola) the regulator is mounted on the back of the alternator body and serves as a sealed lid for an ignition proof chamber for the spark producing components.

Nick is looking at the regulator in electrical terms. It is not integral to the alternator, connects with external wires. It could just as well be mounted on a bulkhead and connected with longer wires and work just as well with the exception of compromising the ignition proof integrity.

Back to your problem, you need to determine beyond question the output voltage before deciding on a remedy. BTW, we have reports of Motorola regs drifting their voltage up on their own. It's time to get a real measurement. Also, an alternator with 15V output may work fine on a Crown Vic police cruiser but such an application does not have a current limited Pertronix 1146A electronic ignition. There are considerations in our application of which Nick may not be aware as he pronounces the alternator healthy.

[pdecker]

Measure alt output connected to load, or open circuit?

Neil, should I have the alternator output wired in when I test the voltage, or test it open circuit with the ground of the meter on the engine?

[joe_db]

Read this thread:

http://www.moyermarine.com/forums/showthread.php?t=8910

Neil, should I have the alternator output wired in when I test the voltage, or test it open circuit with the ground of the meter on the engine?

[hanleyclifford]

One thing you should keep in mind is that voltages vary widely throughout the system when the engine is running. Wiring and consumers of power all have their influence on voltage. You should get a quality digital voltmeter and have good lookaround of your system while the engine is running. You might be surprised at the variations. An alternator putting out 15 volts may work great on a dirty wiring system or one that has many users while the engine is running, while the same alternator will wreak havoc on a clean wiring system. A weak alternator putting out maybe 13.8 volts may service a clean new system nicely. But do not be misled, coil+ is where the rubber meets the road.

[ndutton]

Neil, should I have the alternator output wired in when I test the voltage, or test it open circuit with the ground of the meter on the engine?

Have it wired in. With enough RPM for the alternator to kick in plus a little more, test at the alternator output post, the connected battery post and the small coil + terminal, all tests to a good ground (the small coil - terminal is NOT a ground) and please report back. The state of charge of the battery does not matter as long as it can start the engine.

An alternator putting out 15 volts may work great on a dirty wiring system or one that has many users while the engine is running, while the same alternator will wreak havoc on a clean wiring system. A weak alternator putting out maybe 13.8 volts may service a clean new system nicely.

It has already been determined Phil recently replaced his wiring (post #1 in this thread) so although possible, it's not likely in a typical deteriorated condition. The tests outlined above will indicate harness integrity by actual measurement without speculation.

But do not be misled, coil+ is where the rubber meets the road.

Only within a very narrow view of the ignition system. It is not an indicator of electrical system health and performance anywhere else on the boat. If Phil's measurements come back with a high, potentially damaging output voltage this is a whole boat issue, not just the coil as Joe and I mentioned previously. For example, the initial suggestion of 14.7 ~ 14.8 volts puts the batteries at risk too.

[hanleyclifford]

Have it wired in. With enough RPM for the alternator to kick in plus a little more, test at the alternator output post, the connected battery post and the small coil + terminal, all tests to a good ground (the small coil - terminal is NOT a ground) and please report back. The state of charge of the battery does not matter as long as it can start the engine.

It has already been determined Phil recently replaced his wiring (post #1 in this thread) so although possible, it's not likely in a typical deteriorated condition. The tests outlined above will indicate harness integrity by actual measurement without speculation.

Only within a very narrow view of the ignition system. It is not an indicator of electrical system health and performance anywhere else on the boat. If Phil's measurements come back with a high, potentially damaging output voltage this is a whole boat issue, not just the coil as Joe and I mentioned previously. For example, the initial suggestion of 14.7 ~ 14.8 volts puts the batteries at risk too.

Exactly why I recommend a detailed analysis of all voltages in the system. Edit: The system should be tested hot and running in gear at cruise with all normal users on line such as electric fuel pumps, blowers, electric cooling pumps etc. As an example, on Destiny I might have 14.7 coming off alt+ but lose .1 at the main buss bar. At batt + I might see only 14.2, due to all the consumers bleeding off pressure/voltage. Test each user or supplier/receiver with digital meter.

[pdecker]

Here is the live data!

I tested the engine today with two different coils. First, I had my old Pertronix Flamethrower in, since I forgot that I used it as a backup coil when my new coil failed last weekend. The Flamethrower is rated at 3.0 ohms. It was hard starting but seemed to run smoothly once running. After the test, I disconnected it and wired in the new coil that has already "failed" twice by the engine shutting down after 90 minutes. The engine started immediately and smoothly with the "new" coil installed. Both tests were at about 1200 RPM with blower, instruments, and cabin ventilation fan running, and shore power with battery charger disconnected.

Flamethrower:
Resistance between + and - on the coil, while hot after the test, unconnected: 3.2 ohms
Voltage between + and - on the coil, connected, warm, running: 6.6 V
Voltage between + on coil and ground on engine block: 13.5 V
Voltage from alternator output lug to ground, connected, warm, running: 13.7 V
Voltage on battery banks, connected, warm, running: 13.6 V (both batts separately).
Temperature of coil at end of 30 minute test: 171 F.

New Moyer coil with about five hours on it:
Resistance between + and - on the coil, cold, unconnected: 3.8 ohms
Voltage between + and - on the coil, connected, warm, running: 6.0 V
Voltage between + on coil and ground on engine block: 13.1 V
Voltage from alternator output lug to ground, connected, warm, running: 13.3 V

I did not test the voltage at the batteries again. I also observed that the temperature of the new coil was not rising noticeably during the test, and I did not want to wait around for 90 minutes in the 90 degree Florida heat to recreate the failure today.

From this data, we can calculate the current going to the EI:
Old coil: 13.5 V / 3.2 ohms = 4.2 A --> over the 4.0 A limit.
New coil: 13.1 V / 3.8 ohms = 3.4 A --> under 4.0 A limit.

Conclusions? Old coil = bad. New coil = seems good. If the engine shut off problem happens again, I need to test the coil for spark, and if there is spark, the problem is probably elsewhere.

I read somewhere that the Ignitor EI module shuts down if it overheats and resets once it is cooler. But the engine never gets over 180 F.

What do you think, guys? What's the next step?

[hanleyclifford]

Nice job testing, but I still don't like 13.1 volt at coil+. You don't need it. The A4 will run at 9 volts. I run mine at around 10.5 volts and it remains just barely warm to the touch after running for 10 hours, and the same coil has been doing it for 20 years. I do however, make use of the "R" terminal on the solenoid (Delco) to give full battery voltage while cranking. I suggest you put a 1 ohm 40 watt resistor in front of that Moyer coil.