Lost Spark

[albarnett_99 13]

Need help diagnosing why I've lost spark.  I'm running a MSD 8595 distributor and Blaster 2 coil in a 390 FE.  Battery has 12.49 volts and I get 11.63 volts at the + side of the coil.  However, when I disconnect #1 plug wire and try to ground it, I get nothing.  I also get nothing when I disconnect the coil wire from the distributor and try to ground.

Not sure where to go from here.  Any help you can provide is much appreciated!

[Midlife 814]

Does the distributor turn when you crank the engine?  That's the first thing I would check...

[mwye0627 44]

1 hour ago, Midlife said:

Does the distributor turn when you crank the engine?  That's the first thing I would check...

I remember a time back in 1976, I was driving my 1969 Mustang with a 351W engine down the road when it suddenly quit running...

I got it towed home, and when I checked it out it had no spark...   As it turned out, that was a lucky break for me...    The oil pump had somehow locked up and the roll pin through the distributor gear had sheared off!!!    Replaced the Oil Pump and Roll Pin and life was good again...    

These ignition problems are not Always Electrical...   :)  

[1969_Mach1 333]

Here is some diagnostic info from MSD.  I had to use it once.  Backed my car out of the garage.  Then it wouldn't restart to pull it back in.  I had a no spark condition.  In that case it was the magnetic pick-up inside the dist.

https://www.msdperformance.com/support/troubleshooting_techniques/

[Shep69 149]

This happened to me about a month ago. Im also using MSD gear on my windsor.  Before you do anything open the link that 1969Mach1 posted above and try that . That will eliminate a couple of things. If you have no spark using that method then either your coil is bad or the msd box is faulty.  I had spark so i changed the dizzy cap and magnetic pickup. This fixed my problem.

[1969_Mach1 333]

I realized the OP has a Ready-To-Run distributor.  I don't know how much tech info MSD has to diagnose those.  They have resistance specs for magnetic pick-ups.  So that can be checked.  Coils rarely fail but are easily checked.  Like others mentioned, make sure the rotor is rotating.  Also when checking for spark test it a the coil wire to the distributor as well.  It's very rare, but I have seen a rotor crack and the electrical current from the coil goes directly to ground through the cracked rotor.

[gordonr 4]

As most has mentioned, insure the rotor is turning. If it is do a visual inspection inside the dizzy while the cap is off.  Next inspect the  external ground (black wire) being clean corrosion free and tight.  Next use a test light on both the positive and negative terminals while cranking the engine. Positive terminal should show a steady light. The negative will show flashing on-off-on etc. if it does remove the coil Hi tension wire from the coil and put your test light a little less than 1/4" inside the coil tower and crank to visual see any spark jumping to you test light (You wont get shocked).If it does the the coil wire is bad.  From there if nothing else is found  or If the test light doesnt flash on the negative side, the possibility of excessive current draw from the coil taking out your ignition module in the dizzy or the module just gave up.

[gordonr 4]

Sorry forgot to mention to disconnect your tach wire before the test light diag.

[1969_Mach1 333]

On ‎5‎/‎28‎/‎2018 at 10:36 AM, albarnett_99 said:

Need help diagnosing why I've lost spark.  I'm running a MSD 8595 distributor and Blaster 2 coil in a 390 FE.  Battery has 12.49 volts and I get 11.63 volts at the + side of the coil.  However, when I disconnect #1 plug wire and try to ground it, I get nothing.  I also get nothing when I disconnect the coil wire from the distributor and try to ground.

Not sure where to go from here.  Any help you can provide is much appreciated!

If your distributor rotor rotates and you don't see anything visual or mechanical wrong.  My question is, does that ready-to-run distributor use a simple 4 terminal GM HEI style ignition module?  Let us know.  I am not certain, but thinking it might.  If so, they are easy to test with nothing more than a test light.

[albarnett_99 13]

Thanks to everyone for their replies.  I called MSD Tech Support today and they suggested I put a test light on the negative terminal of the coil and move my distributor ground from the intake manifold to the battery.  Before I attempted any of that, I pulled the distributor cap and validated that the rotor was turning.  Inspected the rotor and cap; all looked normal.

I then put the test light on the coil and it illuminated.  I relocated the ground to the battery and attempted to start.  It fired immediately.  

gordonr or Midlife - what would cause excessive current draw from the coil?

1969_Mach1 - no clue what type of ignition module is used in the MSD

While I am happy it is running again, I am still concerned that I have either a bigger ground issue or resistance problem.  I have been through multiple coils and instances like what happened above over the past 4-5 years.  I have purchased a refurbished harness from Midlife but have held off on installing it.  May have to finally get it done.

[Midlife 814]

When it comes to aftermarket ignition systems, I am no expert. 

That said, relocating a ground suggests that the block is not well grounded.  Do you have the ground strap from the passenger side head to the firewall?  How long ago did you check your battery ground cable?

[gordonr 4]

12 minutes ago, albarnett_99 said:

Thanks to everyone for their replies.  I called MSD Tech Support today and they suggested I put a test light on the negative terminal of the coil and move my distributor ground from the intake manifold to the battery.  Before I attempted any of that, I pulled the distributor cap and validated that the rotor was turning.  Inspected the rotor and cap; all looked normal.

I then put the test light on the coil and it illuminated.  I relocated the ground to the battery and attempted to start.  It fired immediately.  

gordonr or Midlife - what would cause excessive current draw from the coil?

1969_Mach1 - no clue what type of ignition module is used in the MSD

While I am happy it is running again, I am still concerned that I have either a bigger ground issue or resistance problem.  I have been through multiple coils and instances like what happened above over the past 4-5 years.  I have purchased a refurbished harness from Midlife but have held off on installing it.  May have to finally get it done.

If your current was too high it would have ruined your module. With most coils under 1 ohm  you can expect 15 amp draw or less dead headed to keep modules happy. By having a poor ground as in your case the current draw would have been less through the module than with a good ground. 

BTW I would have  installed Midlife's yesterday. 

 

[albarnett_99 13]

Midlife - I have the traditional ground strap from the head to the firewall along with the battery ground to block and block to frame.  About 2 years ago, I upgraded the battery to block and block to frame grounds with 1/0 gauge cables.  All paint was removed and surfaces cleaned.  At that time, I upgraded the cable from the solenoid to starter with the same gauge cable.

After a recent incident of a dancing tach, I decided to check all 3 original grounds and added a couple more.  I added a new ground from the back of the intake manifold to the firewall as well as firewall to frame.  

I have noticed a recurring pattern of the dancing tach just before I lose spark.  Most times, everything dies within a few minutes of the dancing tach.  The car will die with or without the aftermarket tach installed.  The last time it happened, I was able to get the car home before it lost power.  The next day, I had no spark.

[1969_Mach1 333]

When you say dancing tach, is this an original in-dash tach?  If so, how is it connected to your ignition system?

[gordonr 4]

" After a recent incident of a dancing tach, I decided to check all 3 original grounds and added a couple more.  I added a new ground from the back of the intake manifold to the firewall as well as firewall to frame."

A few things are going on here . Besides the ground providing  a  path for the ignition coil to saturate  then release  the high voltage  it is the  power "on" for the module itself to operate.  As with the conversation around the pertronics and bypassing the resistance wire because of low voltage issue  hurting the module,  a poor ground can have the same effect.  Testing electrics is testing for a difference of potential . For example  using your voltmeter on "volts DC" add attaching one lead to the negative battery terminal and the other to where your module ground was bolted. Measuring a ground point to another ground point will measure a difference  of "0" on your meter or "no difference" in a perfect circuit when cranking or running.  In your case it wont be. I would be checking your 4 gauge engine ground as it also supplies the path for your alternators charging system. The acceptable spec with engine  running with all your accessories on is .5 volts or less across your main ground. Your chassis ground can be measured the same way by moving your lead of the intake to a chassis point. Your goal is as close to 0 volts as possible as its responsible  for all the accessories on your car. 

[Midlife 814]

Hmmm....a dancing tach indicates a flakey connection somewhere in your primary ignition system or a coil that goes bad when it begins to warm up.  You could have something as simple as a semi-broken wire inside the insulation (I've seen that happen a couple of times), a bad splice, a not-so-tight connection, etc.

[albarnett_99 13]

Here are some additional updates:

1969_Mach1 - the tach is an aftermarket Autometer

gordonr - I will take your advice and use the multimeter to test all grounds

Midlife - yes the coils get very hot with a big block in a Mustang engine bay.  Interestingly enough, since I installed a stroker motor with ceramic coated headers, engine temps dropped significantly. It runs in 180-190 degree range well below what it did previously.

How do I isolate a wire with a potentially poor connection or splice?  Would I start with the wire that was inserted to bypass the pink resistor wire?  Or do you suggest another?

[Midlife 814]

The only way I know to find a bad wire is to ring it out for continuity, checking for the resistance readings and not the beeping sound used by many folks.  When I find a reading above 1 ohm, I wiggle wire ends to see if that helps.  If significantly above 1 ohm, I probe the wire with a needle reading resistance from one end to that point to isolate where the poor conductivity is located.  I obviously look for bulges in the wire/harness to determine if there was a previous splice. 

Finding bad connections (e.g. loose nuts, poor grounding against painted fenders, etc.) are even harder to find.

[Ridge Runner 1,112]

If you have the old style 6al modual it may have fried ,gone through a couple of them . The new ones are not transistor like the older ones

[albarnett_99 13]

Midlife - not sure if this matters, but the tach operates normally for extended periods of time (no bouncing, no wide swings in reading).  It is usually during a long drive when the tach starts to get erratic. After it gets erratic the car will often die suddenly.  Total loss of power and won’t start for an extended period of time. 

I initially thought it was caused by the coil getting hot. Not sure anymore. 

[Midlife 814]

Sure sounds like a bad coil to me.

[1969_Mach1 333]

The issue sounds like it might be heat related.  Coil like midlife mentioned, or ignition module or magnetic pick-up.  If you have a good hair drier (or carefully with a heat gun) you can try warming the coil.  Then open the dist cap and warm up the ignition module and magnetic pick-up.  This is an attempt to recreate a heat related issue.

[gordonr 4]

All coils get hot just by way of under hood temps. I mentioned dead heading the coil to ground through an amp meter earlier. This does a couple things. It checks the integrity of the coil and stress tests your ignition supply power to the coil. Trying to confirm if there is an intermittent power supply can be difficult. I would find a 194 bulb and socket and  temporarily wire it to the coil power supply and ground the other side. Bring the bulb assembly inside the car and you will have the info you need upon the next failure.  

[albarnett_99 13]

gordonr - not familiar with the term dead heading.  Are you referring to testing the primary and secondary sides of the coil to see if it’s within manufacturer spec?  Or are you referring to your tests of ground?

[gordonr 4]

6 hours ago, albarnett_99 said:

gordonr - not familiar with the term dead heading.  Are you referring to testing the primary and secondary sides of the coil to see if it’s within manufacturer spec?  Or are you referring to your tests of ground?

The term "Dead Head" comes from the current being tested is terminated to ground thru your meter. There is no spec in current draw as the specs are in measurements of "ohms". Whats the difference? Your meter outputs around 1.5 volts when it used in the ohms setting  for measurement.  Imagine having a wire in your harness hanging by a couple strands thats being tested feeding a coil, an ohm meter will show ok, Now disconnect the negative side of your coil while having the positive power supply terminal in place and turn on your ignition. Connect your amp meter in series with the negative terminal to ground.  As a set points being closed with key on engine off your meter will  measure the total current draw of the coil and if there is a loss of voltage  to the positive side of your coil with a second meter set to volts dc  measuring to insure no loss.