No Spark, 6.4v at +coil

[cwestra]

Tried to start my car this morning and found no spark.  Researched a few threads here and found that I should be getting between 9 and 10v at the coil + with ignition switch on.  I am getting only 6.40v with old coil and new one.  Using MP orange box.  Any suggestions.

[dodj]

As a first step, check your bulkhead connector connections, column connections and the ballast resistor. Do you have battery voltage on the ign sw. side of the ballast resistor? If you don't, it could be just poor connections.

[cwestra]

As a first step, check your bulkhead connector connections, column connections and the ballast resistor. Do you have battery voltage on the ign sw. side of the ballast resistor? If you don't, it could be just poor connections.

On the side of the ballast resistor with the 2 heavier wires I am getting 6.8v (run position) and 8.8v (start position).  On the side with the single wire I am getting 10.6v (run position) and 6.1v (start position).

[Bullitt-]

Could be anywhere but as dodj suggested the bulkhead connector is a most common problem area, can have bad connections due to corrosion, also check the wide flat connector on the steering column. Other than those you just need to use your meter to see where the power drop starts, work forward starting at the battery.   

[cwestra]

What voltage ranges should I be seeing at the ballast resistor leads with the 2 ignition positions ("run" and "start") referenced above?  Can someone confirm that these are, in fact, too low?

[Bullitt-]

A fully charged 12V battery should read about 12.6V, check your battery and whatever reading you get (at least in an ideal world) is what you should see on the input side of the ballast resistor. I would expect to see a small drop off on any system due to normal resistance of wires and connections of less than 0.50V. 



See what brother BIGS found when chasing a similar issue  http://www.cuda-challenger.com/cc/index.php?topic=92845.msg917177#msg917177

[cwestra]

Thanks.  I actually did get it running but not sure how.  Here are the voltages I recorded.

Coil +                             8.6 (idle)   /   11+ (rev'd)              6.7 (on position but not running)              10.2 (cranking)
Coil -                              3.4 (idle)   /   7.3  (rev'd)              1.2 (on position but not running)                3.8 (cranking)
Ballast (Ign. side)          8.9 (idle)   /  11.8 (rev'd)              6.8 (on position but not running)              10.6 (cranking)
Ballast (VR side)          12.4 (idle)   /  14.4 (rev'd)            10.9 (on position but not running)                8.1 (cranking)

Battery voltage reads 12.7v.

Buiiltt, you mention wanting to see around 12.6v at BR-Ign (- losses est. < .50v).  Is this in the  "cranking" or "run" position?  I see that my readings indicate I have to much drop for either but I'm curious as to which one you are referring to.

Also, now that the car is running I see that the coil (+) and BR (Ign) have the same readings as before, in the "on" position, but the voltage at the BR (Ign) is now higher in the "cranking" position (10.6v compared to 8.8v before).  I'm not sure what could have caused that except maybe a low battery.  Any thoughts?

I'd still like to know how all these numbers compare against what they should be under these conditions.  Any help would be appreciated.

[Bullitt-]

Cranking will drop available voltage from a full charged 12.6V battery to 9.5V to 11V.   Your battery's relative charge and efficiency of the starter would effect those numbers.
  Your numbers "Ballast (VR side)          12.4 (idle)   /  14.4 (rev'd)" look pretty good but reflect the inefficiency of your charging system at idle, pretty typical from all I've read.
All of the other numbers are relatively lower due to the effect of the ballast resistor that drops the voltage in the "run" position which is a percentage of the available voltage.
  Your voltage shows higher when cranking because the ballast resistor is being bypassed in the "cranking" (many call this "start") position.

     Sounds like maybe you have/had a weak battery. 

[cwestra]

Cranking will drop available voltage from a full charged 12.6V battery to 9.5V to 11V.   Your battery's relative charge and efficiency of the starter would effect those numbers.
  Your numbers "Ballast (VR side)          12.4 (idle)   /  14.4 (rev'd)" look pretty good but reflect the inefficiency of your charging system at idle, pretty typical from all I've read.
All of the other numbers are relatively lower due to the effect of the ballast resistor that drops the voltage in the "run" position which is a percentage of the available voltage.
  Your voltage shows higher when cranking because the ballast resistor is being bypassed in the "cranking" (many call this "start") position.

     Sounds like maybe you have/had a weak battery. 

Sounds, good.  Thanks for the detailed analysis.  Very much appreciated.

[dodj]

When you are looking at the column connector with the large gauge wires, look closely at the red wire and it's metal connectors. Make sure they are clean and tight. There have been several pics from members posted about this wire melting the connector from overheating due to poor contact/corrosion.

[cwestra]

When you are looking at the column connector with the large gauge wires, look closely at the red wire and it's metal connectors. Make sure they are clean and tight. There have been several pics from members posted about this wire melting the connector from overheating due to poor contact/corrosion.

Thanks.  I will check that out this morning.

[j72440rallye]

I seem to remember an article in mopar muscle stating that you could bye bypass the resistor without any ill effects so long as you do not have a points set-up.  This would give you the full 12 volts to the coil.