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Discussion Starter · #1 ·
I have an MSD 6520 hooked up in my 80 Cutlass. Just did an engine swap and was at the point of checking for spark. There is no spark, started checking voltages etc. There is no power at the MSD and no power at the coil. Tried a few things the instructions and Holley site said to try like using a number wire to harness/coil and no spark. No lights coming on on the MSD. Is the box cooked? Or what else should I be trying. Not a new MSD or coil, was given to me with the new engine I bought. Back working on it this weekend and trying to figure out more thanks guys.

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The large red wire goes to battery + voltage. Do you have power here?
The small red wire goes to an ignition switch sourced power. Do you have power here?
Black wire is ground.
The LED only flashes when there is a trigger signal from the distributor. Also for low or high supply voltage. Each time a trigger signal is received it will flash. At idle, you may see the flash, but at higher speeds, the led appears to be lit continuously.

You will not see power at the coil + with a MSD...Because the MSD is a Capacitive Discharge ignition and it receives a direct 12 volt source from the battery, there will not be any voltage at the Coil Positive (+) terminal even with the key turned On. During cranking or while the engine is running, very high voltage will be present and no test equipment should be connected.

CHECKING FOR SPARK If triggering the ignition with the White wire: Figure 11 Checking for Spark with the White Wire. WHITE WIRE TRIGGER Figure 12 Checking for Spark with the Mag Pickup. MAGNETIC PICKUP TRIGGER 1. Make sure the ignition switch is in the “Off” position. 2. Remove the coil wire from the distributor cap and set the terminal approximately 1/2" from ground. 3. Disconnect the MSD White wire from the distributor’s points or ignition amplifier. 4. Turn the ignition to the On position. Do not crank the engine. 5. Tap the White wire to ground several times. Each time you pull the wire from ground, a spark should jump from the coil wire to ground. If spark is present, the ignition is working properly. If there is no spark skip to step 6 on page 10:

If triggering with the Magnetic Pickup: 1. Make sure the ignition switch is in the “Off” position. 2. Remove the coil wire from the distributor cap and set the terminal approximately 1/2" from ground. 3. Disconnect the MSD magnetic pickup wires from the distributor. 4. Turn the ignition to the On position. Do not crank the engine. 5. With a small jumper wire, short the MSD’s Green and Violet magnetic pickup wires together several times. Each time you break this short, a spark should jump from the coil wire to ground. If spark is present, the ignition is working p

What are you using as a trigger? What type and brand distributor?



Here's the instruction sheet...https://documents.holley.com/6520.pdf

Don't touch any bare wires while triggering or running, you will get knocked on your ash.
 

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For MSD,

The MSD box will drive the coil, both wires
The two large cables, as stated above, directly to the battery, red, positive, black, negative.
The SMALL red wire should go to the IGN or IGNITION terminal on the stock fuse box, which gives a full 12 volts in ignition switch start and run positions, and no current flow in the rest of the switch positions.

The two wire connector in your hand goes the corresponding connector from the distributor, plugs right in. These are the magnetic trigger wires

Alternate WHITE wire, trigger for other electronic and points ignition systems, DO NOT GROUND THIS WHITE WIRE, OR, NO SPARK.

A couple of words, yet again, on coils, DON'T MOUNT THEM ON THEIR SIDES. Not even the useless epoxy ones on the car, mount it in a stock Chevrolet coil mount, upright. And, check the coil for defective, and not with an ohm meter, Take the coil off the car, and to a parts store with an off vehicle electrical tester, let it run, let it get HOT, operating temperature.
 

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Discussion Starter · #4 ·
So everything is wired properly as you said, large red to battery and small red to ignition and proper ground. All connections are good. There is still no live reading directly at the MSD box. It somehow has no power going through it. When using a jumper wire to trip the green and purple wire there is still no spark. It’s an MSD pro billet I believe. Going to test the ignition coil and pickup coil here
 

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By using either test method, you effectively remove the pickup coil or trigger method from the equation. When you make and break the connection, you should see the led blink once indicating a trigger event. The other test method involves shorting the white wire to ground. I would try that also to rule out a wiring deficiency in the green and violet wires.

It's possible that you have a defective coil.

If you substitute a known working coil and still see no spark, the MSD box is junk.
 

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Discussion Starter · #6 ·
I’ll see about picking up another coil and trying it. Is there anything that would cause the MSD to not power up? Such as no oil pressure? It has a terminal for psi
 

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I’ll see about picking up another coil and trying it. Is there anything that would cause the MSD to not power up? Such as no oil pressure? It has a terminal for psi
I'm not aware of any oil pressure requirements or lockouts for this unit.

To get the unit to power up requires 12 volt to the larger wire and 12 volts to the small red wire and a good ground. Tap the white wire to ground and the led will flash and you'll see a spark. No spark means bad coil or bad box.
 

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Discussion Starter · #8 ·
Alright well thank you very much for your help. I’ll see about getting some new stuff here and get it working. Sorry about any dumb questions, first time dealing with one of these units myself. Thanks again!
 

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Hate to tell you the Digital 6 is a failure prone unit. The one I have died and they replaced it under warranty than a year later it died again, too bad for you they pretty much told me. My buddy gave me his old 7AL2 after he went to a 7AL3, put it in my car and have not had any trouble with it. If you look on You tube there is some kind of test to see if the box is bad or not to test MSD units.
 
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