MSD

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Ahoey

Ahoey

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I have an MSD streetfire ignition. In the instructions it tells you to hook the heavy red wire directly to the battery, heavy black to ground or negative post. The ignition works fine but the unit draws power with the key in the off position. Question 1, is this normal? checked wiring against instructions several times, positive it’s correct. Question 2, can I wire a relay to shut power off to MSD box when key is off? Any help is appreciated.
 
If it's anything like a 6AL-2, there should be a thinner red wire that connects to a switched 12v that triggers an internal relay that closes the circuit for the heavy red wire. Is that not the case?
 
mopowers said:
If it's anything like a 6AL-2, there should be a thinner red wire that connects to a switched 12v that triggers an internal relay that closes the circuit for the heavy red wire. Is that not the case?
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This is the wiring diagram I used from the msd installation Manual. Using the stock electronic distributor. It seems to be a plug and play package.
 
Is this small red wire connected to a switched 12v source? If so, my understanding is that no current should be drawn from the large red battery wire until 12v is applied to that small red wire. No additional relays should be necessary. If that small red wire has constant power, then that may be why there's a constant draw.

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mopowers said:
Is this small red wire connected to a switched 12v source? If so, my understanding is that no current should be drawn from the large red battery wire until 12v is applied to that small red wire. No additional relays should be necessary. If that small red wire has constant power, then that may be why there's a constant draw.

View attachment 1716311883
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Wouldn’t the +original coil wire be on switched power?
 
As said in post 4 hook that small red wire to switched power and all will be good . Good luck .
 
my guess would be because the small red wire is getting power when the key is off
 
And just how much power is being drawn? You should be able to not modify the factory wiring, and disconnect the original coil + wire, connect that wire ONLY to the small red

Also be absolutely CERTAIN you have NOTHING connected to the coil EXCEPT the two wires from the MSD. If you have a tach, use MSD destructions, and you may need a tach adapter. DO NOT connect your tach to the coil at all
 
67Dart273 said:
And just how much power is being drawn? You should be able to not modify the factory wiring, and disconnect the original coil + wire, connect that wire ONLY to the small red

Also be absolutely CERTAIN you have NOTHING connected to the coil EXCEPT the two wires from the MSD. If you have a tach, use MSD destructions, and you may need a tach adapter. DO NOT connect your tach to the coil at all
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Haven’t tested it yet but have a suspicion about the ignition switch. Thanks
 
The ign coil is powered from the MSD box, not the ign sw. You can see that in post #3.
 
Ok. I have completely disconnected the msd box from the car. When you put the meter between the power wires to battery, neg. Or pos. I get a 12 reading. The small red wire is disconnected. I guess the msd box is fubared
 
with the small red wire unhooked you should not get power to the coil positive wire . the two main wires going to the battery will show power full time . if that makes sense .
 
jimjimjimmy said:
with the small red wire unhooked you should not get power to the coil positive wire . the two main wires going to the battery will show power full time . if that makes sense .
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Not really because it kills my battery. My way of thinking is that there should be no power draw from ignition box when key is off
 
there should not be any draw if the small red wire is unhooked if there is i don't know whats wrong .
 
Where's the current draw? Does the orange wire have power with the small red wire disconnected? That small red one is the 'trigger' wire so to speak. With that disconnected, there should be no draw. The large red wire will still show 12v because it's connected to the battery - at least it should be.
 
jimjimjimmy said:
there should not be any draw if the small red wire is unhooked if there is i don't know whats wrong .
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The stock electronic ignition worked well just no rev limiter. Need a new tach anyway so I’ll have to shop around. Any suggestions
 
mopowers said:
Where's the current draw? Does the orange wire have power with the small red wire disconnected? That small red one is the 'trigger' wire so to speak. With that disconnected, there should be no draw. The large red wire will still show 12v because it's connected to the battery - at least it should be.
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When I put the meter between the battery and the wires that the instructions say either neg or pos unit is drawing power. All other wire disconnected
 
is there any power to the coil pos wire with the small red wire unhooked
 
Ahoey said:
Ok. I have completely disconnected the msd box from the car. When you put the meter between the power wires to battery, neg. Or pos. I get a 12 reading. The small red wire is disconnected. I guess the msd box is fubared
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If you are using a VOLT meter scale to measure this it is telling you nothing. This is sometimes known as 'phantom' voltage or current, and is caused by the very high sensitivity of the voltmeter. Put the meter into current and see if it shows current. Start with the highest scale of your meter, IE 10A or 20A and work down

HOW TO DO

Disconnect ONLY the big red. Leave the black connected. Put one meter probe, measuring current, on the hot terminal you connected the MSD to, and the other probe on the disconnected big red wire end. If you read a very few milliamps, it is fine
 
if there is no power at the coil pos with the small red wire unhooked your good and power when hooked up your good
 
You need to see if the MSD box is the problem.

It is very simple:
- leave the thick red & black wires connected to the battery
- disconnect all other wires.
- check for voltage on the thin red wire. If it has voltage, the box is defective.

A cheap fix, cheaper than a new box, with rev limiter:
- Cheap HEI dist [ Chinese, they work well ]
- MSD # 83647 4 pin module [ this mod has an adj rev limiter, mounts in place of existing module ]
 
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