Return to the home page...

Go Back   Moyer Marine Atomic 4 Community - Home of the Afourians > Discussion Topics > Ignition System

Reply
 
Thread Tools Display Modes
  #1   IP: 73.255.216.151
Old 05-02-2016, 08:51 PM
romantic comedy's Avatar
romantic comedy romantic comedy is offline
Afourian MVP
 
Join Date: May 2007
Location: florida
Posts: 1,912
Thanks: 13
Thanked 118 Times in 100 Posts
resistor before or after coil

I was thinking that some boats might be wired with a wire from the positive of the coil for a source of 12v to something else. Maybe the fuel pump?

If this is the case, the resistor before the coil would reduce the voltage to this wire.

Am I thinking right here? It has been a while since circuits class.
Reply With Quote
  #2   IP: 107.0.6.242
Old 05-02-2016, 09:13 PM
hanleyclifford's Avatar
hanleyclifford hanleyclifford is offline
Afourian MVP
 
Join Date: Mar 2010
Posts: 6,978
Thanks: 172
Thanked 280 Times in 226 Posts
Talking

Quote:
Originally Posted by romantic comedy View Post
I was thinking that some boats might be wired with a wire from the positive of the coil for a source of 12v to something else. Maybe the fuel pump?

If this is the case, the resistor before the coil would reduce the voltage to this wire.

Am I thinking right here? It has been a while since circuits class.
You are thinking right, and that is the reason why the ignition should have a dedicated circuit.
Reply With Quote
  #3   IP: 24.152.132.65
Old 05-02-2016, 09:46 PM
ndutton's Avatar
ndutton ndutton is offline
Afourian MVP
 
Join Date: May 2009
Location: Torrance, CA
Posts: 9,619
Thanks: 198
Thanked 2,208 Times in 1,425 Posts
Quote:
Originally Posted by romantic comedy View Post
I was thinking that some boats might be wired with a wire from the positive of the coil for a source of 12v to something else. Maybe the fuel pump?

If this is the case, the resistor before the coil would reduce the voltage to this wire.

Am I thinking right here? It has been a while since circuits class.
Put the resistor between the '-' coil post and the EI black wire. Issue solved.
__________________
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
Reply With Quote
The Following User Says Thank You to ndutton For This Useful Post:
edwardc (05-02-2016)
  #4   IP: 73.255.216.151
Old 05-02-2016, 09:54 PM
romantic comedy's Avatar
romantic comedy romantic comedy is offline
Afourian MVP
 
Join Date: May 2007
Location: florida
Posts: 1,912
Thanks: 13
Thanked 118 Times in 100 Posts
I thought this when I was reading a thread about poor running. Maybe it will help someone.

I have points and no resistor.
Reply With Quote
  #5   IP: 107.0.6.242
Old 05-02-2016, 10:02 PM
hanleyclifford's Avatar
hanleyclifford hanleyclifford is offline
Afourian MVP
 
Join Date: Mar 2010
Posts: 6,978
Thanks: 172
Thanked 280 Times in 226 Posts
Talking

No matter where you put the resistor, an accessory fed from coil+ is going to affect the voltage being delivered to the coil - IMO ignition should have a stable voltage, not affected by things going on and off. Besides a fuel pump connected at coil+ should have OPSS shut off capability. In fact ignition and fuel pump should be wired for shut off in the event of a shut down. I have both circuits on independent OPSS switches. I learned a while back not to crowd too much onto an OPSS>
Reply With Quote
  #6   IP: 24.152.132.65
Old 05-02-2016, 10:06 PM
ndutton's Avatar
ndutton ndutton is offline
Afourian MVP
 
Join Date: May 2009
Location: Torrance, CA
Posts: 9,619
Thanks: 198
Thanked 2,208 Times in 1,425 Posts
It's a reasonable concern. Better yet for those with EI, get a Moyer coil and keep your alternator output voltage within reason (like 14.4 volts or less) and there's no need for a resistor. If that sounds familiar, we've only said it about a hunnert times.

edit:
In a properly designed and executed electrical system additional loads fed from the coil '+' post DO NOT affect the voltage greater than 3%. If measurements indicate otherwise, the ignition system wiring is too small for the loads and must be increased. You don't just keep adding loads without revisiting wire gauge as it pertains to voltage drop. We've said that a hunnert times too.
__________________
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; 05-02-2016 at 10:11 PM.
Reply With Quote
The Following User Says Thank You to ndutton For This Useful Post:
Administrator (05-03-2016)
  #7   IP: 12.216.194.200
Old 05-03-2016, 06:26 AM
smosher smosher is offline
Afourian MVP
 
Join Date: Jun 2006
Posts: 489
Thanks: 0
Thanked 35 Times in 34 Posts
The resistor has to be tied in series between the coil and ground.
It doesn't matter if its tied to the + side of the coil and the Ignition voltage
or tied between the - side of the coil and the black wire of the ei. Its still in series which reduces the amp flow through the primary side of the coil.

fwiw I have mine tied between the -side of the coil and the black wire from the ei. No Issues.

To calculate accurately your ballast resistor size, measure the ignition voltage with the batteries fully charged. The goal is to keep the amperage below 4 amps, according to pertronix. I believe that between the coil resistance and the ballast resistor added together should be @ 4 ohms.
Reply With Quote
The Following User Says Thank You to smosher For This Useful Post:
ndutton (05-03-2016)
  #8   IP: 107.0.6.242
Old 05-03-2016, 07:58 AM
hanleyclifford's Avatar
hanleyclifford hanleyclifford is offline
Afourian MVP
 
Join Date: Mar 2010
Posts: 6,978
Thanks: 172
Thanked 280 Times in 226 Posts
Talking

Since everyone is restating their opinion on coils and voltage, I will do likewise: no more than 12 volts should be permitted at coil+ nor should any other loads be fed from coil+. It should always be possible to at least briefly hold your hand on the coil of a running engine. That is my position after more than half a century working on 12 volt ignition systems.
Reply With Quote
  #9   IP: 24.152.132.65
Old 05-03-2016, 08:53 AM
ndutton's Avatar
ndutton ndutton is offline
Afourian MVP
 
Join Date: May 2009
Location: Torrance, CA
Posts: 9,619
Thanks: 198
Thanked 2,208 Times in 1,425 Posts
Steve,
I'd like to propose a minor refinement to your post (which I thanked BTW):
Quote:
To calculate accurately your ballast resistor size, measure the ignition voltage with the batteries fully charged and at sufficient RPM for the alternator to be producing a charge.
The difference could mean as much as 1˝ ~ 2 volts and affect the resistor value calculation.
__________________
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
Reply With Quote
The Following 2 Users Say Thank You to ndutton For This Useful Post:
Administrator (05-03-2016), Bratina (05-03-2016)
  #10   IP: 107.0.6.150
Old 05-03-2016, 08:59 AM
hanleyclifford's Avatar
hanleyclifford hanleyclifford is offline
Afourian MVP
 
Join Date: Mar 2010
Posts: 6,978
Thanks: 172
Thanked 280 Times in 226 Posts
Talking

It should go without saying that all calculations pertaining to the coil should be considered with engine warmed, running at cruise rpm, and electrical system at equilibrium.
Reply With Quote
  #11   IP: 12.216.194.200
Old 05-03-2016, 12:39 PM
smosher smosher is offline
Afourian MVP
 
Join Date: Jun 2006
Posts: 489
Thanks: 0
Thanked 35 Times in 34 Posts
Quote:
Originally Posted by ndutton View Post
Steve,
I'd like to propose a minor refinement to your post (which I thanked BTW):
The difference could mean as much as 1˝ ~ 2 volts and affect the resistor value calculation.
Hi Neil, Yes you are right, engine running and alternator producing.

Steve
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Coil Tests Tim Ignition System 53 09-24-2015 05:47 PM
Coil Failure dvd Electrical 14 10-25-2011 05:35 PM
Hot Coil and High Alternator Output Triton106 Electrical 53 10-02-2011 07:12 PM
engine stops Possum Troubleshooting 4 04-20-2011 09:19 AM
Hi, new member with a problem cpdeeley Introductions 10 01-11-2009 01:43 PM


All times are GMT -4. The time now is 04:47 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.


Universal® is a registered trademark of Westerbeke Corporation

Copyright © 2004-2024 Moyer Marine Inc.

All Rights Reserved