PLEASE HELP IM IN DIRE STRAIGHTSNo spark MSD but test fine what am i missing!

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J.B.

J.B.

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Ok guys need some mopar help !!

I caught a random start two times past few days but havent been able to again.

Just bought a 72 challenger from a 19 year old whos grandfather passed as he needed money for college. He couldn’t figure out how one day it starts and the next few days it doesnt and so on bit was otherwise a stellar restored car. It has had intermittent starting issues since he got it. He replaced new coil, wires, plugs, starter relay, and neutral safety switch but still no success. The challenger has a 360 LA block with msd conversion that was all checked for proper wiring as well.

my problem is im not getting spark while crabking but have 12v to msd box

Here is what i have done to diagnose.

1. I checked the battery to block ground at
0 ohms.
2. I checked the firewall to block ground at
0 ohms
3. I have 12v of switch power and cranking power to the MSD 6a
4. I did the jumper test per MSD of the green and purple distributor trigger wire connection from the MSD 6a to coil, took coil wire distributor side off and grounded it to block then took screw driver and jumped the starter relay with key in on position with screwdriver and watched excellent spark popping off.
5.checked with test light IGN1 brown which was from positive coil under column and on bothside of bulk head
6. Checked blue/white-trace with test light on both sides of bulkhead
7.checked connection of 12v little red feed wire and its receiving the power from ign1 and ign 2
8. yellow cranking wire from ignition switch test lights up while cranking.

So what the hell is going on here i have complete spark down to spark plugs doing the trouble shoot jumping the magnetic Trigger wires with key on but cranking i have nothing dead as a door nail?

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Step 1. Pull all MSD and associated wiring off and find the nearest trash can.

Step 2. Install Mopar Electronic ignition.

Sreo 3. Drive and enjoy your car.
 
Not a bad idea can i buy all new under hood wiring
 
What distributor are you using? MSD, Chrysler electronic w/MSD box, or something else?
If it's the Chrysler electronic with the MSD box, make sure the polarity is correct going to the pickup in the distributor. Some of the newer repro (offshore) Chrysler distributors have been reported to be reversed from the get-go- colors were right, polarity was wrong.
If it's an MSD distributor made in the last 10 years, then I'm with Rusty.
 
I don't know "much" about electrical, but I can say with 100% certainty that 95% of starting issues on here are due to aftermarket bs stuff.
You won't get much better advice than what Rusty said.
Do a search on here for "MSD" and you will see the amount of threads.
Or switch to HEI.
 
4spdragtop said:
I don't know "much" about electrical, but I can say with 100% certainty that 95% of starting issues on here are due to aftermarket bs stuff.
You won't get much better advice than what Rusty said.
Do a search on here for "MSD" and you will see the amount of threads.
Or switch to HEI.
Click to expand...
Ok i will switch to electronic mopar kit
 
Please understand, I'm not an MSD hater. It has its place and lots of people like it. It's just a personal opinion of mine that the Mopar ignition can do anything that the MSD can do, even on an all out race car. Having said that, if you DO decide to go with another ignition, it would be very wise to diagnose what you have FIRST, in case the problem is elsewhere. If you go to all the trouble to change ignition systems, you want it FIXED.
 
You need to tie start qnd run circuits together with the small red wire. It sounds like what may be happening when the car intermittently starts is that it rolls over quick enough and catches the run circuit when the key pops back to that position. I have seen this happen many times with New MSD installs.

If the car still has ballast resistor wiring you can tie start and run together there and tag the little red wire to one of the terminals.

Personally I've had very good luck with MSD ignitions for the last 25 years. I still have my original 7al to box that I purchased in 2002 and MSD tested it a okay this spring.

On the other hand I have had nothing but problems with the Mopar ICM. Between bad modules faulty pickups and of course the beloved ballast resistor issues I am more of a Pertronix fan. As in I made 576whp on nitrous with an Igniter 1 points replacement module. Similar to the MSD I've had no issue with the points replacement modules in 25 years or more.
 
Car doesnt have ballast resistor, are you saying its wired wrong? The start and run circuit is ties all together to the red is this what you mean?

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I am saying you need to get a test light or a voltmeter and verify that you have a start circuit and a run circuit and they are both tied to the little red wire that turns the MSD on. Typically the Run circuit is dark blue and start circuit is brown. You need to be firing the MSD while the engine is cranking over and when the key returns to the Run position.
 
the problem is the MSD box needs at least 2 volts all the time and our Mopar OEM wiring cuts or often deduces the 12 volts except to the ignition side when cranking. So if you tie into the cranking circuit as soon as you let the key back when it barks...it dies.

to prove this run a hot wire directly from from the battery to the MSB box (red / switched wire) and have someone yank it off once it starts and continues to run. When the 12volt power is cut, the engine will die.

I usually grab two separate constant 12 volt circuits off the ballast resister, one circuit that has the 12 volts when the key is "on" and a separate 12 volt circuit that has power while cranking the engine.

test light will not cut it unless you can notice the light getting dimmer when you are cranking the starter. On mine, the voltage would drop just enough to no longer give enough signal (12 volts) to the fire the MSD box
 
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Jeremiah (jd) said:
I am saying you need to get a test light or a voltmeter and verify that you have a start circuit and a run circuit and they are both tied to the little red wire that turns the MSD on. Typically the Run circuit is dark blue and start circuit is brown. You need to be firing the MSD while the engine is cranking over and when the key returns to the Run position.
Click to expand...
I guess you didnt read my full post i test light and confirmed 12c from blue and brown and they are tied together and in both cranking and run i had 12v and no spark
 
J.B. said:
I guess you didnt read my full post i test light and confirmed 12c from blue and brown and they are tied together and in both cranking and run i had 12v and no spark
Click to expand...

Then the next troubleshooting step would be as mentioned by Denny is to run a temporary wire from the battery to the little red wire. If that does not solve your issue you likely have an issue in the distributor and it is not triggering the Box.
 
HemiDenny said:
the problem is the MSD box needs at least 2 volts all the time and our Mopar OEM wiring cuts or often deduces the 12 volts except to the ignition side when cranking. So if you tie into the cranking circuit as soon as you let the key back when it barks...it dies.

to prove this run a hot wire directly from from the battery to the MSB box (red / switched wire) and have someone yank it off once it starts and continues to run. When the 12volt power is cut, the engine will die.

I usually grab two separate constant 12 volt circuits off the ballast resister, one circuit that has the 12 volts when the key is "on" and a separate 12 volt circuit that has power while cranking the engine.

test light will not cut it unless you can notice the light getting dimmer when you are cranking the starter. On mine, the voltage would drop just enough to no longer give enough signal to the box.
Click to expand...
I have this done per instructions brown coil positive and switched blue wire white trace from ballast wiring tied together with the little red 12v feed wire to mad 6a
 
Jeremiah (jd) said:
Then the next troubleshooting step would be as mentioned by Denny is to run a temporary wire from the battery to the little red wire. If that does not solve your issue you likely have an issue in the distributor and it is not triggering the Box.
Click to expand...
I thought the box is triggered by ignition and sends spark to coil then coil energizes distubutor? The distributor feeds msd box?
 
J.B. said:
I thought the box is triggered by ignition and sends spark to coil then coil energizes distubutor? The distributor feeds msd box?
Click to expand...

a constant 12 volts is required all the time to keep the MSD box "alive". There are separate leads that go to the coil and separate leads to the distributor and a separate 12 volt "trigger" is needed to tell the box to "turn on" and do its thing.
 
J.B. said:
I have this done per instructions brown coil positive and switched blue wire white trace from ballast wiring tied together with the little red 12v feed wire to mad 6a
Click to expand...

and how is that working? the problem is as previously explained.

If you put a meter on the red trigger wire to the MSD box, I would bet that either a) it is only hot when cranking or b) it is NOT maintaining a minimum of 12 volts while cranking.
 
HemiDenny said:
and how is that working? the problem is as previously explained.

If you put a meter on the red trigger wire to the MSD box, I would bet that either a) it is only hot when cranking or b) it is NOT maintaining 12 volts while cranking
Click to expand...
Is there a possibility my distributor pickup is shot not allowing spark
 
I just put a 6al on my silver Duster and Butch's red Duster and have 2 tied to dual crank triggers on the Butch Leal / Direct Connection Hemi race car.

I love them. besides the 2-step rev limiter, you could weld with the spark.

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J.B. said:
Is there a possibility my distributor pickup is shot not allowing spark
Click to expand...

anything is possible.....but why guess?????. Do the simple test I gave you.
 
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This is what I'm talkin about. You're in good hands with these fellers. They're liable to get you right on track using your MSD and that would be the least cost and work.
 
J.B. said:
Can you tell me you did that what wires did you use
Click to expand...

wired as their instructions said.

2 leads to the distributor (green / purple)
2 leads to the coil (orange / black)
1 smaller red trigger wire to constant 12 volts (minimum) **** here is your issue

1 large red to battery
1 black lead to ground

grey wire to tac (normally green wire from tac)
blue wire to 12 volt from line loc when ativated

not bad from memory huh???
 
So i need a constant 12v thats hot all the time and the brown and blue switched ignition hot to the small red?
 
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