#1
IP: 75.74.240.203
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Coil issue? Runs for 90 minutes and quits
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 |
#2
IP: 71.118.13.238
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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 |
#3
IP: 173.48.103.104
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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.
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#4
IP: 24.152.132.65
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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.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others Last edited by ndutton; 04-15-2015 at 11:52 PM. Reason: added hybrid comment so as not to be too absolute |
#5
IP: 72.45.14.161
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14.7 will have you replacing batteries AND coils.
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#6
IP: 75.74.240.203
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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? |
#7
IP: 24.152.132.65
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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.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
The Following User Says Thank You to ndutton For This Useful Post: | ||
HalcyonS (04-06-2016) |
#8
IP: 72.45.14.161
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Also note some people use aftermarket regulators on the Motorola and leave the stock reg in place as a spark shield, me included
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#9
IP: 75.74.240.203
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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?
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#10
IP: 72.45.14.161
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#11
IP: 107.0.6.242
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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.
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#12
IP: 24.152.132.65
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__________________
Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
#13
IP: 107.0.6.242
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Last edited by hanleyclifford; 04-16-2015 at 08:40 PM. |
#14
IP: 75.74.240.203
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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? Last edited by pdecker; 04-19-2015 at 01:22 PM. Reason: copied too much |
#15
IP: 107.0.6.242
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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.
Last edited by hanleyclifford; 04-19-2015 at 03:10 PM. |
#16
IP: 24.152.132.65
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Here we go again
Hanley and I have very different views on the subject and frankly I'm weary of the exercise. Regarding coils and electronic ignition, the following are FACTS and not subject to interpretation:
Same example, different numbers. Coil input 14.2 volts and a Moyer 4.3 ohm coil. Whaddya think now? Huge input voltage per Hanley's rule yet the system amperage is 3.3 amps WITHOUT any supplemental resistance. Notice too that without supplemental resistance you'll have two less wire connections aka potential failure points in the primary ignition wiring. My point is - now and for the past several years - amperage - amperage - AMPERAGE! Within reason, the coil input voltage does not matter as long as the system has sufficient resistance via coil, supplemental resistor or a combination of both to render the system amperage below 4 amps (per Pertronix). Good engineering practice is to build in a margin of safety below the maximum.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
#17
IP: 107.0.6.242
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#18
IP: 24.152.132.65
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Is there any question the example system is doomed to failure? Even at 9 volts? How about 8 volts? Following your voltage rule, no fair calculating amperage, it's volts only. We have members coming here for help with what was once a vexing problem (successfully resolved a few years ago) and sending them down a 'voltage only' path that might work depending on whatever coil they might have picked up at the local auto parts boutique (there are 3/4Ω coils too) just adds confusion. There's more to it than just voltage. Don't get me wrong, voltage is a factor but not the only factor. We have to give these members the whole picture if they are to become self sufficient and expert troubleshooters. Isn't that really the goal? Kelly's 'Coil Input Information" thread should be required reading as a condition of forum membership. I can't believe after solving the problem nearly 3 years ago we are still going through this. edit: Phil, I apologize to you for the haranguing on your thread. There is a great deal of information in the forum archives on this problem. Your boat, your choice, the solution is ultimately up to you. Best of luck.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others Last edited by ndutton; 04-19-2015 at 08:48 PM. |
#19
IP: 107.0.6.242
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Does anyone know what is the minimum amperage that will fire the coil and run an A4?
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#20
IP: 73.55.66.163
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this is all covered by a simple linear relationship:
E=IR, which says that voltage equals amps times resistance. Amps=volts divided by resistance. It seems simple to me: You get a coil that has resistance, what ever that is. You have an alternator that has a voltage, whatever that is. Plug these into the equation, and you find the amperage. If it is over 4 amps, you add resistance by adding a resistor. |
#21
IP: 24.152.132.65
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RC, yes it's as simple as that, has been all along. Don't forget to build in a safety cushion. It's risky designing to the ragged edge.
__________________
Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others Last edited by ndutton; 04-19-2015 at 09:07 PM. |
#22
IP: 107.0.6.242
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#23
IP: 107.0.6.242
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You are sounding rather authoritative (authoritarian?) tonight, Neil. The question is a reasonable one. I know from many years of hot rodding and working on engines that no increase in performance comes from increasing an already adequate spark. At 6 to 1 compression do we really need 4 amps?
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#24
IP: 73.55.66.163
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Good question Hanley. I thought that the 4 amps was an "accepted limit".
Maybe not? Also, I am making it a bit simpler then it actually is. I just dont want to get into more advanced concepts when this way would work just fine in calculating the current. It is about making spark, and could be considered independent of the engine. The accepted 4 amps, I understand, is the upper limit of current for the battery-coil system. As long as the spark is made and the engine runs at a lower current, it would work fine. Is longevity an issue? Would a coil have a shorter, and less reliable life at 4 amps versus less? I dont know, do we have data on this issue? |
#25
IP: 107.0.6.242
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Tags |
coil, ignition coil, resistor |
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