1 more coil voltage question - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 01-01-2003, 09:16 AM Thread Starter
Journeyman
 
FNjeep's Avatar
 
Join Date: Mar 2002
Location: Northeast,Pa.
Posts: 132
Thanks: 0
Thanked 0 Times in 0 Posts
 
1 more coil voltage question

thanks for bearing with me all, but this has been kicking the crap out of me. I was wondering how much voltage I should have at the neg. coil terminal in the run and start positions. I was also wondering if anyone knows of a link for jeeps of the sequence/systems to check for no-start conditions. I found one for another type vehicle when the search was down that said I should have voltage there but not how much.quick recap: 78 cj-5 w/304 "can" type coil. low voltage in run(6.5) but it does come up somewhat now in the start pos.(9-10) whereas it was dropping to 1.something, although it's very low on the neg. side.(mid 2s) the coil tested ok at the parts store, but i'm leaning towards picking up a new and mounting it in an upright position as this one has been mounted on it's side. the mod. also tested good, and yesterday I replaced the distributor with a rebuilt, new cap,rotor,plugs and wires but still no spark getting to plugs. thanx for all the help so far. Happy New Year, and hope everyones not feeling it too much today, specially after trying to follow this train wreck. Alex
FNjeep is offline  
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 01-01-2003, 11:37 AM
 
Join Date: Oct 2002
Posts: 852
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: 1 more coil voltage question

Do you have the prestolite or motorcraft system?

My 77 had the prestolite system and it was common to have the module go bad once or twice a year so I got a rebuilt point dist and switched it and I didn't notice a performance decrease. Plus its easy to carry a spare set of points and condenser in the glove box. I just had to add the resister to the + side of the coil. I've changed many a motorcraft module too.

I have found those module test not to be very accurate I've found many times they test good but still are the problem.

Are you testing the voltage with the wire on the - side or off?
the module may be taking voltage away if its hooked up. It should be close to the same voltage on both sides with nothing hooked to the - side. A resistance test is more accurate then a voltage test though.

Can type coil failures are rare I can count on 1 hand the number I have seen bad in 20+ years and a few of them were from a hole being worn in them from being mounted wrong.

Modules on the other hand are the cause of a no start 90% of the time and pickup coils/wiring the other 10% from my experiance anyway. If it was me I would run a ground wire from the batt. - to the module (a bad ground can fry them quick) and replace the module. I'd almost bet money thats your problem




in2mud is offline  
post #3 of (permalink) Old 01-01-2003, 01:32 PM Thread Starter
Journeyman
 
FNjeep's Avatar
 
Join Date: Mar 2002
Location: Northeast,Pa.
Posts: 132
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: 1 more coil voltage question

I have the motorcraft system. I got a new pick-up coil with the dist. also tried with a new module(the one that was in was bad, but my spare checked out ok) though I haven't spliced into it yet, i'm just trying to get it to start right now. when I checked for voltage on the -side everything was hooked up like it would be if i was going to run it (painless kit couple of green and a purple for tach? seems excessive but it's been like this without trouble for quite a while. Thanx for the info,Alex
FNjeep is offline  
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 01-01-2003, 03:38 PM
Official Historian
 
WILL's Avatar
 
Join Date: Sep 1999
Location: Hot Springs, AR
Posts: 8,339
Thanks: 1
Thanked 5 Times in 5 Posts
 
Re: 1 more coil voltage question

It's not supposed to have full battery voltage in the run position.
WILL is offline  
post #5 of (permalink) Old 01-01-2003, 04:12 PM
Way Outta Control
 
Join Date: Sep 1999
Location: The Palouse
Posts: 13,432
Thanks: 1
Thanked 3 Times in 3 Posts
 
Re: 1 more coil voltage question

TFI and OEM Coils:
1. Full battery voltage in the Start postion.
2. About 8.4 to 8.7 volts in the Run position.

LEVE is offline  
post #6 of (permalink) Old 01-02-2003, 10:45 AM Thread Starter
Journeyman
 
FNjeep's Avatar
 
Join Date: Mar 2002
Location: Northeast,Pa.
Posts: 132
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: 1 more coil voltage question

thanks for the info so far guys, I touched on some of this in an earlier post, and I know I'm about 2 volts shy in both run and start, but my main concern now is the disparity in voltage on the neg. side of the coil. I'm only reading in the mid 2s in both positions and was wondering if this should throw up any red flags for me to check anything specifically.I'm planning on trying a new mod. and coil tomorrow, after I get one of those butane soldering irons to splice into the mod. I'm outdoors and don't want to run 100+ feet of extension cord for it.
FNjeep is offline  
post #7 of (permalink) Old 01-02-2003, 02:08 PM
Way Outta Control
 
Join Date: Sep 1999
Location: The Palouse
Posts: 13,432
Thanks: 1
Thanked 3 Times in 3 Posts
 
Re: 1 more coil voltage question

1. Don't worry about the negative side of the coil.
2. You don't have any control over it....
3. Until you undersand Kirchoff's law... the above statement don't make sense.
4. Remember that if the input voltage is low... the voltage at the other end of the coil will also be low...
5. So...
6. You're just gonna have to trust me. [img]images/graemlins/grin.gif[/img]
LEVE is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups 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 email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



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
Trackbacks are On
Pingbacks are On
Refbacks are On

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