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-   -   Ignition / Electrical Gremlins (http://www.clubcobra.com/forums/ignition/138713-ignition-electrical-gremlins.html)

cycleguy55 06-30-2017 04:27 PM
Ignition / Electrical Gremlins
 
Environment:
  • MSD 8477 distributor
  • MSD 6A analog ignition control box p/n 6200
  • MSD Blaster 2 coil (mounted vertically)
  • Optima Yellow Top battery in trunk - unknown vintage (I've had car 3 years, and it was in it when I bought the car)

Scenario:
  1. Car running fine no problems.
  2. Shut car off, came back 10 minutes later and there was barely a click from the starter when I turned the key. Voltmeter showed 11 volts (14+ when engine running).
  3. Had recently been having some hot start issues that seemed to be getting worse, so thought perhaps battery was failing. Replaced battery and got a small spark when hooking up ground - that tells me something was drawing power.
  4. A few key turns with weak 'clicks' from starter, but then starter engaged and engine turned over like crazy - but it wouldn't fire. There's fuel, but no spark.
  5. Coil was wet on top, appeared to be oil. Touched coil and it was so hot I almost burned myself. Removed + / - wires and checked battery again - no spark. Coil was hot electrically and thermally, even with ignition off.
  6. Noticed gauges (e.g. voltmeter, electric coolant and oil temperature) were no longer working. Switched 12V electric accessory outlet also dead. Hmmmm
  7. Replaced coil with new coil, heard a 'pop' from MSD box when + /- wires to coil touched each other (not a good sound, suspect I now have problems with MSD 6a - but that's secondary). No longer any current draw on coil with ignition off.
  8. Still lots of cranking, but no spark.
  9. Have checked all the fuses I could find, none of them have blown.

Questions:
  1. One suggestion I got was to look at the ignition switch - could this have failed, leaving ignition on and coil energized, while at the same time not providing current to gauges and accessory outlet?
  2. Could MSD 6A box fail in such a way as to cause coil to remain hot with ignition off?
  3. Other suggestions?

Gaz64 06-30-2017 04:56 PM
Hi Brian,
I would say you are replacing the 6A module now, shorting the black and orange on the coil has probably blown a large capacitor in the module.
Sounds like the module is always on, and being triggered somehow while the engine is not running?

Do you know how to perform the spark test on an MSD ignition?
The test quickly determines a module fault, a coil fault, wiring or distributor as the cause for no spark.

Gary

cycleguy55 06-30-2017 05:39 PM
Quote:
Originally Posted by Gaz64 (Post 1424964)
Hi Brian,
I would say you are replacing the 6A module now, shorting the black and orange on the coil has probably blown a large capacitor in the module.
Sounds like the module is always on, and being triggered somehow while the engine is not running?

Do you know how to perform the spark test on an MSD ignition?
The test quickly determines a module fault, a coil fault, wiring or distributor as the cause for no spark.

Gary
My biggest and first concern is whatever caused this in the first place - is that a fault in the MSD 6A, or is it possible a failed ignition switch caused the: a) MSD 6A and coil to remain energized even though the switch was in the 'Off' position) ; and b) gauges and accessory power to become inoperative even when the switch was in the 'On' position? In nearly 50 years of driving I don't recall ever having an ignition switch failure.

I've used MSD diagnostics / troubleshooting before, so I'm comfortable with that. I'll work through that and figure it out once I get the big problem sorted out.

MikeInOH 06-30-2017 07:08 PM
I would suggest laying under the dash and check the electrical spade connectors especially on the ignition switch but also gauges etc. I chased a number of ghosts in my superformance when I first got it (car was 15yrs old) and it turned out to be some simple loose connections. I ended up slightly crimping each spade and putting a dab of dielectric grease on all of em and havent had a single issue since. These cars have a ton of vibration so tight connections are key. Its an easy thing to rule out....good luck

Gaz64 06-30-2017 07:09 PM
Hi Brian,

It does sound like a ignition switch issue with both scenarios.

The MSD modules switches a primary voltage of 400-500 volts to the coil depending on model , but only when triggered by the distributor, as in engine spinning above 100 rpm.

If the module is somehow faulty, then it could be the reason for the on/off of the coil primary circuit.

Especially if the coil is hot with a cold engine that has not run for some time.

I would check to see what voltage is at the coil, be wary that the coil positive (orange) is at 400 volts plus with engine running normally, so be careful if this is in fact somehow "live", while the key is off.

I have replaced one ignition switch on one of my cars in 37 years.

But ignition switch failure is becoming more of an issue in some cars these days.

Gary

CompClassics 06-30-2017 08:43 PM
I actually just had a client that had a very similar problem with his 1972 Corvette with a Pertronix and a MSD Balaster 2 coil. Check your supply voltage to the coil (+) post when the engine is running, if the supply voltage is greater than 12.5V you may have found the problem (you should not have anything more than 12.5V). My client had recently replaced his alternator with a higher output unit, the supply voltage to his coil was greater than 14V causing the coil to overheat and fail. I figured out how much to reduce the voltage with resistors, installed a resistor assembly and he has not been left on the side of the road since.

520SC 06-30-2017 09:18 PM
This will reduce your coil supply voltage from alternator output voltage (14V -
14.5V) down to 12.5V

http://www.ebay.com/itm/1-4-External...pRdYo9&vxp=mtr

https://i.ebayimg.com/images/g/dU8AA...Yo9/s-l500.jpg

Gaz64 06-30-2017 09:45 PM
Coil voltage is not 12 volts like inductive ignition systems.

450 volts typical of capacitive discharge ignitions, CDI.

cycleguy55 07-01-2017 11:27 AM
Thanks for the ideas / comments / suggestions.

I'll start with some basic sleuthing (E.g. do I have power to the MSD box, is the ignition switch the cause of that, etc.), then go on to coil voltage, etc. Obviously I can't check running voltage until such time as I can actually get it running, but definitely something to do when I get there.

Question (which perhaps is due a thread all on its own): If the MSD 6A is blown, do I replace it with another, or switch out the MSD distributor as well and go to an all-in-one Pertronix distributor? If the latter, I'm leaning toward the Ignitor II version, FWIW - just due to the ability to use regular coils. Or I guess I could go Ignitor III and carry a spare coil.

Thoughts?

CompClassics 07-01-2017 02:50 PM
You should be able to run the MSD distributor as a stand alone without the amplifier box.

Texasdoc 07-01-2017 03:49 PM
Quote:
Originally Posted by CompClassics (Post 1425030)
You should be able to run the MSD distributor as a stand alone without the amplifier box.
Not the 8477 distributor. Per MSD's website:
"These distributors require the use of a separate ignition box, such as an MSD 6, 7, 8, or 10 Series ignition."

If you don't want a CD ignition, you need another way to fire the coil since that distributor doesn't have an ignition module.

(I've got a CB Performance Black Box that I am planning on installing. It will take the magnetic pickup from the distributor and output to the coil or the 6AL. That way if my 6AL box dies on me, I can switch two wires and keep going. I just haven't installed it yet. )

Gaz64 07-01-2017 07:58 PM
Quote:
Originally Posted by Texasdoc (Post 1425033)
Not the 8477 distributor. Per MSD's website:
"These distributors require the use of a separate ignition box, such as an MSD 6, 7, 8, or 10 Series ignition."

If you don't want a CD ignition, you need another way to fire the coil since that distributor doesn't have an ignition module.

(I've got a CB Performance Black Box that I am planning on installing. It will take the magnetic pickup from the distributor and output to the coil or the 6AL. That way if my 6AL box dies on me, I can switch two wires and keep going. I just haven't installed it yet. )
I am very keen to try one the CB Black boxes.

Fully programmable, high energy module all in one.

cycleguy55 08-05-2017 12:37 PM
Surge / Miss: Ignition or Carburation?
 
I've got the car running again, but get a surge / miss on light throttle cruise between 2,000 and 2,500 RPM. There's also more exhaust 'popping' or 'burble' on throttle-closed deceleration than before I replaced the ignition box and coil. There are no apparent issues at idle, when accelerating, or cruising < 2,000 RPM. I have not yet checked the timing but, other than replacing the magnetic pickup and distributor cap, the distributor was not touched.

Environment:
  1. MSD 8477 distributor (magnetic pickup swapped from old MSD 8577 distributor in process of getting car running)
  2. Summit Multi-Spark digital ignition control box p/n , mounted behind dash ( https://www.summitracing.com/parts/sum-850610 )
  3. Summit Epoxy coil ( https://www.summitracing.com/parts/sum-850500 )

Questions:
  1. Does this sound like an ignition or a fuel issue?
  2. Where do I start?

Texasdoc 08-05-2017 02:06 PM
Usually popping on decel is lean fuel.

Gaz64 08-05-2017 09:59 PM
MSD is known for poor rotor phasing.

They make an adjustable rotor to correct it if wrong.

cycleguy55 08-07-2017 11:06 AM
Quote:
Originally Posted by Gaz64 (Post 1427730)
MSD is known for poor rotor phasing.

They make an adjustable rotor to correct it if wrong.
I'm running the same rotor I had before changing the ignition box - and all was well before that. Can 'poor rotor phasing' happen overnight or while the car isn't running?

cycleguy55 08-07-2017 11:11 AM
Quote:
Originally Posted by Texasdoc (Post 1427697)
Usually popping on decel is lean fuel.
And the surge / miss feels to me like a classic 'lean surge'. It was worse when I finally got the car running after 3+ weeks, then seemed to fade after being driven a bit. The biggest improvement was in the first 5-10 miles, then less after that.

I wonder whether the 3+ weeks of not running and the hot weather we had evaporated the fuel in the carb and left some deposits / varnish behind that are causing the problem.

I'm going to try running some carb or fuel system cleaner through it and see if that helps or resolves the problem. If not I'll be pulling the carb and tearing it apart.

Gaz64 08-07-2017 06:28 PM
Quote:
Originally Posted by cycleguy55 (Post 1427837)
I'm running the same rotor I had before changing the ignition box - and all was well before that. Can 'poor rotor phasing' happen overnight or while the car isn't running?
You have changed from an analogue 6A to a digital summit.
I know changing from 6A to 6AL causes issues with rotor phasing.
Get a spare distributor cap, drill a large hole in the top, and observe phasing with a timing light.

Texasdoc 08-23-2017 09:47 AM
Another thought is to make sure you connected the new Summit 6AL box to the distributor correctly. Does your distributor have green and violet wires or two black wires? MSD in their infinite wisdom made the wire colors wrong. If you have two black wires, make sure the black wire with the orange stripe connects to the violet wire on the Summit box. The black wire with the violet stripe goes to the green wire. The black wire with the violet stripe DOES NOT go to the violet wire!

cycleguy55 08-24-2017 01:53 PM
Quote:
Originally Posted by Texasdoc (Post 1428811)
Another thought is to make sure you connected the new Summit 6AL box to the distributor correctly. Does your distributor have green and violet wires or two black wires? MSD in their infinite wisdom made the wire colors wrong. If you have two black wires, make sure the black wire with the orange stripe connects to the violet wire on the Summit box. The black wire with the violet stripe goes to the green wire. The black wire with the violet stripe DOES NOT go to the violet wire!
My distributor has one wire that's black with green and the other is black with violet. The black wire with the orange stripe is connected to the violet wire on the Summit box, and the black wire with the violet stripe goes to the green wire. The polarized plug and colour coding on the wiring is exactly the same as MSD so therefore pretty difficult to get wrong. That's not surprising considering MSD makes these boxes for Summit.


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