Coil issue? Runs for 90 minutes and quits

[hanleyclifford]

Good to hear that you are closing in on a solution. That run down the ICW must have been nerve racking. Your voltage at alt+ sounds a little low but your voltage at coil+ is in a very safe range. Your experience demonstrates that this is not a "one size fits all" matter that is quickly and arbitrarily solved. It would be interesting to know what your amperage is thru coil+: far below 4 amps, I'll warrant. 0-10 amp analog gauges can be had for $4 plus shipping.

[BunnyPlanet169]

Phil - 13.2 VDC is really low for an alternator output - is that measured right on the alternator? Where's the ground? 13.2 is barely charging, that's lower than nominal float charge of about 13.4. Here's where focusing on coil voltage potentially ignores other problems....

[hanleyclifford]

Phil - 13.2 VDC is really low for an alternator output - is that measured right on the alternator? Where's the ground? 13.2 is barely charging, that's lower than nominal float charge of about 13.4. Here's where focusing on coil voltage potentially ignores other problems....

Focusing on one voltage point is perilous indeed. Saturday I did a check on Destiny and found voltage at alt+ to be 14.8v. At the main buss bar the reading (which displays on my digital voltmeter) was 14.26. Voltage at fuel pump was 13.2v and coil+ was 10.5v to 11.0v. Clearly, voltages can (and should be) all over the map. Each one is important for reason(s) specific to loads and position in the distribution "tree". I do agree that Phil needs to address his voltage at alt+ but the specific target voltage is a function of many parameters most of which are specific to each boat.

[Administrator]

Focusing on one voltage point is perilous indeed. Saturday I did a check on Destiny and found voltage at alt+ to be 14.8v. At the main buss bar the reading (which displays on my digital voltmeter) was 14.26. Voltage at fuel pump was 13.2v and coil+ was 10.5v to 11.0v. Clearly, voltages can (and should be) all over the map. Each one is important for reason(s) specific to loads and position in the distribution "tree". I do agree that Phil needs to address his voltage at alt+ but the specific target voltage is a function of many parameters most of which are specific to each boat.

What!?

Bill

[hanleyclifford]

What!?

Bill

Yeah, it's "messy". When the engine is running voltages can vary all over the system.

[ndutton]

It's time to put a stop to this

Yeah, it's "messy". When the engine is running voltages can vary all over the system

I'm sure it's "messy" on some boats but the cold hard fact is the ABYC* specifies an allowable maximum 3% voltage drop on essential circuits. What this means is if you're measuring more than a 3% loss on a circuit, you need to redesign the circuit with larger wire** to mitigate the loss. Adding loads to an existing circuit (electric fuel pump, electric coolant pump, whatever) affects the voltage drop so these additions mean the entire circuit needs to be re-evaluated from source to end. That is basic electrical system design and proper execution.

For example, if your alternator output is 14 volts, you should not measure anything less than 13.6 volts anywhere in the boat's low voltage system.*** If you do, it's time for a wiring upgrade to handle the loads properly.

Clearly, voltages can (and should be) all over the map.

No they shouldn't and the ABYC is clear on this point. Measuring objectionable voltage drops all over one boat does not establish the standard for everyone else to follow. Analyzing your own reported numbers using 14.8V alternator output**** as a starting point:

Main buss @ 14.26V = 4% voltage drop, already substandard
Fuel pump @13.2V = 11% voltage drop, nearly 4 times the allowable ABYC standard
Coil + @ 10.5 - 11.0V = probably have resistor(s) in the circuit so the calculation would be skewed

Don't agree? Take it up with the ABYC and the NEC (National Electric Code)*****

Before repeating your "voltages can (and should be) all over the map" belief, for your benefit and that of the forum with Don's good name at the top of every page I implore you to read the ABYC Standard on allowable voltage drop (ABYC E-11.14.1.2.7). It is clearly presented, not subject to interpretation or opinion.


Footnotes:
* and the entire electrical industry
** poor connections, wire damage, etc. notwithstanding. We're not talking ignition secondary either so don't go there.
*** for essential circuits. Non-essential circuits are allowed a 10% voltage drop per the ABYC
**** far too high for conventional lead acid batteries according to Dan Pires, owner of the iconic Newport Beach Marine electrical business Lewco Electric. They've specialized in marine charging systems for 60 years.
***** Citations available if you really need them

[warefuller]

Power

Wow, you guys had a lot to say between 4/15 and 4/19. Don't know why the thread is listed in the 'current' ones on the web site.

But anyway, it is Power, not current (amps) that heats the coil. Power (Watts) is the product of amps x volts.

Furthermore, to get a bit more technical: In operation, it is not a DC system , but an AC system. In an AC system, particularly with an inductive load (the coil), the voltage and current are not in sync - one lags the other. That is why one needs a true RMS power meter to accurately measure power in an AC system. This may not be a big deal. Just shooting my mouth off.

[ndutton]

Actually Ware, there are other contributing factors, dwell being a big one. Electronic ignition has roughly twice the dwell of points ignition and we found that to be the tipping point in old coil destruction when 'upgrading' to EI.

The extreme example is leaving the ignition on when the engine is not running. There is a 60% chance the coil will be energized (@ the dwell of EI) although in real life it seems it's more like 95%. This is the ultimate dwell scenario and is guaranteed to cook off a coil in short order regardless of voltage, resistance or current.

The AC nature of the ignition system is more accurately a modified RMS system with only the positive side of the squared off sine wave and an unbalanced frequency partially as a function of dwell.

edit (added after HC's following post):
RMS = Root Mean Square

[hanleyclifford]

Wow, you guys had a lot to say between 4/15 and 4/19. Don't know why the thread is listed in the 'current' ones on the web site.

But anyway, it is Power, not current (amps) that heats the coil. Power (Watts) is the product of amps x volts.

Furthermore, to get a bit more technical: In operation, it is not a DC system , but an AC system. In an AC system, particularly with an inductive load (the coil), the voltage and current are not in sync - one lags the other. That is why one needs a true RMS power meter to accurately measure power in an AC system. This may not be a big deal. Just shooting my mouth off.

Not sure what RMS is but I do have a multi meter that gives good readings everywhere in addition to the gauges on the boat which agree with the multi meter. As you are late to the party you will soon see that this is an ongoing issue on this forum. Looking forward to your future input.

[hanleyclifford]

If you think this forum chases it's tail on the subject - have a chuckle with this one: http://board.moparts.org/ubbthreads/.../443002/2.html

[smosher]

Wow, you guys had a lot to say between 4/15 and 4/19. Don't know why the thread is listed in the 'current' ones on the web site.

But anyway, it is Power, not current (amps) that heats the coil. Power (Watts) is the product of amps x volts.

Furthermore, to get a bit more technical: In operation, it is not a DC system , but an AC system. In an AC system, particularly with an inductive load (the coil), the voltage and current are not in sync - one lags the other. That is why one needs a true RMS power meter to accurately measure power in an AC system. This may not be a big deal. Just shooting my mouth off.

If I remember correctly the freq at which the dist revolves has little effect
on the inductance on the circuit. As the freq increases the inductance increases. I did the calc and its posted.

Steve