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

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J.B. said:
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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If it starts, but stops when you release the key, it's the ballast resistor. Usually on the driver's side firewall. It's white, about 3/4 x 3/4 x 4"
 
J.B. said:
The magnetic pickup base needed adjustment and baseplate must of got bumped off set pin
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I just saw this thread on the weekly email I get from the forum on popular threads. As soon as I read the beginning of the thread I was almost 100% sure that the issue was with the magnetic pickup gap being too wide. I used to sell a ton of MSD boxes back in the 80's and 90's and I ended up having to diagnose a ton of no start issues. One thing that happened all the time was that customers would install an MSD box on a car that was running perfectly and as soon as they installed the box the car would not start. We would check the box and it was working fine, and the installs would also be correct. The issue was with the magnetic pickup gap being too wide. It seems that the factory box can pick up a signal if the gap is a bit too wide, but the MSD box could not. So, your car could have the pickup gap be twice as wide as it needs to be and still run fine with the OEM trigger box, but it will not run with the MSD box.
 
HSDemon said:
I just saw this thread on the weekly email I get from the forum on popular threads. As soon as I read the beginning of the thread I was almost 100% sure that the issue was with the magnetic pickup gap being too wide. I used to sell a ton of MSD boxes back in the 80's and 90's and I ended up having to diagnose a ton of no start issues. One thing that happened all the time was that customers would install an MSD box on a car that was running perfectly and as soon as they installed the box the car would not start. We would check the box and it was working fine, and the installs would also be correct. The issue was with the magnetic pickup gap being too wide. It seems that the factory box can pick up a signal if the gap is a bit too wide, but the MSD box could not. So, your car could have the pickup gap be twice as wide as it needs to be and still run fine with the OEM trigger box, but it will not run with the MSD box.
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That should be easy to check and correct. It's the same as setting the gap on a set of points. Let the guy know what the gap should be.
 
To check the distributer pick up, connect test light ground to battery positive terminal, other end to coil negative terminal. test light should flash when engine is cranking.
 
HSDemon said:
I just saw this thread on the weekly email I get from the forum on popular threads. As soon as I read the beginning of the thread I was almost 100% sure that the issue was with the magnetic pickup gap being too wide. I used to sell a ton of MSD boxes back in the 80's and 90's and I ended up having to diagnose a ton of no start issues. One thing that happened all the time was that customers would install an MSD box on a car that was running perfectly and as soon as they installed the box the car would not start. We would check the box and it was working fine, and the installs would also be correct. The issue was with the magnetic pickup gap being too wide. It seems that the factory box can pick up a signal if the gap is a bit too wide, but the MSD box could not. So, your car could have the pickup gap be twice as wide as it needs to be and still run fine with the OEM trigger box, but it will not run with the MSD box.
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That was exactly my problem i closed the gap to a folded in half dollar bill another guy told me. It snaps on and fires quick now!
 
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