YJ Ignition conversion to MSD - JeepForum.com
 
LinkBack Thread Tools
post #1 of 7 Old 05-29-2019, 08:45 AM Thread Starter
lakelotman2
Registered User
1990 YJ Wrangler 
 
Join Date: May 2015
Location: Rome
Posts: 11
YJ Ignition conversion to MSD

90 YJ 4.2 bypassed computer installed MSD distributor years ago, Then last year she needed a new alternator and yep I probably picked the one with most amp out. So the charge is going to the ignition module and apparently that is what is burning ignition module since i have replace it over 6 times and it would crank and run after. So anyone know what resister to put in front of it?

lakelotman2 is offline  
Sponsored Links
Advertisement
 
post #2 of 7 Old 05-29-2019, 09:29 AM
Siva283
Registered User
 
Siva283's Avatar
1993 YJ Wrangler 
 
Join Date: May 2011
Location: Baltimore
Posts: 4,686
Your ignition gets power from the battery. It only pulls what it needs. I think your issue is elsewhere. I however dont know your set up so I cant offer any real help. So heres a bump for you to keep it up in the list

1995 YJ. 2 inch BDS Spring lift. 1 inch shackle lift. 1.25 inch JKS Body Lift 33x12.5x15's. Engo 10,000 pound winch.

Quote:
Originally Posted by Magnum View Post
I gave the Jeep the required offering of $$, sweat, and blood, and everything works fine now. -- Jim
Quote:
Originally Posted by ldso View Post
. It started with a $200 axle, and a few thousand dollars later I was done :)
Quote:
Originally Posted by Luuca View Post
diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

Ask me how I know...
Quote:
Originally Posted by Overhead View Post
this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.
Siva283 is offline  
post #3 of 7 Old 05-29-2019, 11:00 AM
bpounds
Web Wheeler
 
bpounds's Avatar
1988 YJ Wrangler 
 
Join Date: Jun 2013
Location: Whittier
Posts: 3,037
You need to know whether the MSD distributor you have is supposed to have a ballast resistor, or if it is supposed to get a full 12v source. If it was designed to get the 7-9v like the original, blasting it with 12v will burn them out.

Your original distributor used the lower voltage, and the resistor was in the form of a resistor wire. Not a resistor mounted somewhere like was commonly used on other vehicles at the time. The resistor wire was just a yellow wire, same color as all the other ignition power wires that run all over the place, and it was really easy to confuse it or not realize that it was something special. The length of that wire was important. Every inch cut off of it would result in higher volts to the distributor (not a good thing). Usually you will find it was looped back and forth on itself, inside the firewall loom, so that it would be much longer than was really needed to reach the distributor. Another common mistake is to cut off all the extra wire, in an effort to make it nice and tidy, resulting in higher than designed voltage.

I have no idea what your MSD needs, but I think you are right to consider it as the problem. MSD makes a ton of different stuff, even plain old replacement coils that are nothing but OEM equivalent. So time to figure out what you've got, or maybe the path of least resistance (pun) is to just replace it next time it fails with a CRT HEI distributor, which definitely needs a full 12v source.

Bill
Jeepers drive high!
1988 Wrangler,4.2L I-6, Howell EFI JP-1,CRT HEI Ign,AX15 ext slave conversion, Zone 2.5" lift + 1/2" booms, BFG 31 x 10.5, Bestop.
bpounds is offline  
 
post #4 of 7 Old 05-29-2019, 11:10 AM
1project2many
Registered User
1995 YJ Wrangler 
 
Join Date: Oct 2018
Location: Lakes Region
Posts: 351
Coil for use with ballast resistor is different from coil for use without. Most electronic ignitions limit current so resistor not necessary but that's not a definite rule. We usually check the resistance of coil with ohmmeter to tell. If you need a resistor there are many apps to get one from. 1991 XJ is probably an easy one stocked at many stores.
1project2many is offline  
post #5 of 7 Old 05-29-2019, 07:52 PM
Que89YJ
Web Wheeler
2004 LJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit
Posts: 25,625
Actually if the ballast resistor is still installed going to the MSD it would source voltage too low causing high current and burn the coil out.

Sent from my SM-G955U using Tapatalk

Fault codes:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Mean Max pics of everything:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

How to use Google to search the forum:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

No Start:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Que89YJ is offline  
post #6 of 7 Old 05-29-2019, 09:25 PM
bpounds
Web Wheeler
 
bpounds's Avatar
1988 YJ Wrangler 
 
Join Date: Jun 2013
Location: Whittier
Posts: 3,037
Quote:
Originally Posted by Que89YJ View Post
Actually if the ballast resistor is still installed going to the MSD it would source voltage too low causing high current and burn the coil out.

Sent from my SM-G955U using Tapatalk
Good point!

Bill
Jeepers drive high!
1988 Wrangler,4.2L I-6, Howell EFI JP-1,CRT HEI Ign,AX15 ext slave conversion, Zone 2.5" lift + 1/2" booms, BFG 31 x 10.5, Bestop.
bpounds is offline  
post #7 of 7 Old 05-30-2019, 04:30 AM
1project2many
Registered User
1995 YJ Wrangler 
 
Join Date: Oct 2018
Location: Lakes Region
Posts: 351
Reducing voltage through the primary winding below the expected level typically results in weak or no spark. Without enough current the coil never reaches saturation. A current limiting module would never switch to limiting mode while a time based switch such as points or a simple electronic ignition will follow the same "on-off" pattern regardless of current. This same situation occurs when a "12V coil" is installed on a 6V system with a ballast resistor or when saturated injectors are used with a peak-and-hold injector driver.

FWIW when I look up an MSD distributor for the 4.2 the only one listed is part no 8516 which is designed to be used with a complete MSD ignition and blaster coil 8228.


The MSD coil compatibility list doesn't list the 8228 coil but notes that "A ballast resistor is not necessary with any MSD Series Ignition but can be left in-line if originally equipped." This suggests that the MSD uses a current limiting switch and that failing ignitions are not likely to be caused by a missing ballast resistor.

If an actual diagnosis is requested I think more complete information is required.

Edit: Wanted to say I agree fully with this:
Quote:
just replace it next time it fails with a CRT HEI distributor
There is a reason MSD ignitions have earned the name Must Soon Die in some circles. Run a 7 series or trailer it home. lol.
1project2many is offline  
Reply

Tags
alternator , ignition , ignition module , msd , YJ

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may 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
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome