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How to Troubleshoot an MSD 6A/6AL Ignition Control

By: Todd Ryden | 09/03/2020 < Back to Motor Life Home

Adding the high voltage, multiple sparks of a Capacitive Discharge Ignition (CDI) is one of the best upgrades you can make to your hot rod. Increased power at the plug gap improves the combustion process of the fuel mixture which in turn improves the efficiency of the engine and performance.


One of most popular CD ignitions available is the MSD 6A series. There are different models available that all have unique features and accessories. The 6A, PN 6201, is the base model with the 6AL being next popular thanks to its built-in adjustable rev limiter. Both of these ignitions are easy to install on nearly any 4, 6 or 8-cylinder engine running a distributor.


Though MSD builds these ignitions to be as heavy-duty as possible, there are still times when it may be necessary to check out your ignition system to confirm everything is working as it should. Intermittent issues can generally be tracked down to a faulty ground or loose connection and if you have trouble starting your engine, there are easy steps to take to confirm the operation of your ignition. Before getting into those steps, let’s review a few installation tips to confirm the system is installed properly and for best operation. 


A multimeter is an essential tool to any automotive electrical diagnostic test.


Installation Tips

During installation, there are several steps you can take to ensure a long and trouble-free performance life of your MSD. Mounting the ignition, routing of the wires and using high quality terminals for each connection are important. The 6A is designed to be installed under the hood but is recommended to be mounted away from direct heat sources such as the exhaust system. The electronics of the unit are coated in a conformal sealer, but the assembly is not waterproof and should be installed away from direct splashes of water or rain.


Once the unit is mounted, it’s time to focus on the wiring. An MSD must be connected directly to the positive battery terminal to ensure that its transformer and capacitor receive a direct 12 volt power supply. This is the heavy gauge red wire paired with a matching size (10-gauge) ground wire. Ideally, the ground wire would also be connected to the battery, but it can also go to the engine block or chassis ground – but make sure there is a quality engine-to-frame ground strap.


Another connection that should be scrutinized prior to installation is the switched 12 volt source wire for the small gauge red wire. This wire turns the MSD on and off with the ignition switch. Generally, it will be connected to the wire that used to go to the coil’s positive terminal. It is very important to check for 12 volts on this wire when the key in on (in the run position) as well as during cranking. Some older vehicles had a bypass that occurred during cranking and when that happens the reduction in voltage during cranking will essentially turn the MSD box off. Make sure to test the 12 volt on/off wire while cranking the engine!


There are several other simple installation tips for the rest of the wires. The paired black and orange wires are the ONLY wires that will be connected to the coil terminals (black to negative, orange to positive). These wires are carrying over 480 volts so be cautious of touching or connecting any wires while the engine is running. Also, be sure to route these wires separately from the from the other wires, especially the magnetic pickup harness to prevent electrical interference.


The mag pickup harness is one of two ways to trigger the MSD; a magnetic pickup from a distributor (or crank trigger) or the points/amplifier white wire. These wires will never be used at the same time and care should be taken in routing the trigger wires, especially the mag pickup harness. It is best to route this harness away from the two coil wires and any spark plug wires. Running it along a fender well or the block creates a ground plain for the harness to reduce any electrical interference.

Troubleshooting Tips

MSD has always built the 6A series of ignitions to be as robust as possible. In fact, each ignition is run under load on a test stand for over two hours to ensure full operation. That said, if you’ve experienced an issue or no-start situation, there are several items you can easily troubleshoot to assist in determining if the ignition is at fault, or move on to another system on your vehicle.


Your troubleshooting should always start with the battery terminal connections while confirming the condition of the battery. If you’re not using the negative terminal for ground (which is the preferred method), make sure your ground source is clean, tight and there’s a path from the engine to the chassis and to the battery.


First thing to check is the status of the LED on the housing of the MSD. With the key in the on position (not running), the LED should flash five times to indicate all systems are go. If not, check the battery connections and the battery itself. The battery needs to be fully charged and in good health, then check the MSD connections to the battery positive terminal as well as the ground. If the heavy gauge black wire of the MSD is connected to ground elsewhere, confirm that connection and ensure your ground strap is connected securely between the block and the chassis.


Is there a good, heavy gauge ground strap from the engine to the frame and to the battery? If not, you better get one!



Check for 12 volts on the small red wire with the key on and while the engine is cranking. Many applications experience a voltage drop during cranking which will cause a no start situation.


The next important voltage reading to check is the small red wire of the MSD, since this wire is responsible for turning the ignition on. After checking the connection and terminal condition, use a volt meter to check for 12 volts with the key in the on position. Next, have someone crank the engine over while checking for voltage as well. This is very important as on a lot of older vehicles there was a bypass that supplied higher voltage to the coil during cranking to assist in cold starts. Since the factory wiring is no longer connected to the coil, an interruption in the voltage could cause the engine to try to fire, then fail and try to catch again. You need to confirm 12 volts during cranking. (Make sure the car is in park and all wires are clear of the fan and any moving parts.)


The only two wires connected to the coil are the Orange and Black wire from the MSD. Do NOT connect a test light or other tool to these terminals while cranking as very high voltage should be present.


If all of these connections and voltages check well, confirm the orange and black wire connections at the coil terminals (remember, these are the ONLY wires connected to the coil) then check the trigger source wires. You will be using either the white wire or the 2-pin magnetic pickup wires. Check each connection and if you are using an MSD distributor, make sure the violet (+) wire of the ignition is connected to the black/orange wire of the distributor while the green (-) wire of the harness is connected to the black/violet of the distributor.

Field Testing/False Trigger

Remove the coil wire from the distributor cap and place it about ½” from ground. A spark is going to jump from the wire to ground, so make sure there is no fuel sources or residue near-by.


After checking all of the voltages and connections as listed above, it’s time to physically check the output of the MSD. Thankfully, there’s a simple way to trick the ignition into sending a spark to the coil which confirms that it is wired correctly and working properly. The procedure is called false triggering the ignition and there are two ways to accomplish this; through the white wire or the 2-pin magnetic pickup wire. (Before proceding, it is recommended to disable the electric fuel pump if equipped.)


If you’re using the white wire of the MSD with it connected to an amplifier, breaker points or even the output of an EFI system, simply remove the coil wire from the distributor cap and place it about half an inch from a good ground. Make sure the wire is away from any fuel supply or fumes as you’re going to be causing a spark to jump from the wire to ground. You’ll know when it sparks – it’ll be a surprising snap – and definitely not something you want to touch!

Next, turn the ignition to the on position (no cranking) then take the white wire and tap it to ground several times. This process should trigger the MSD sending a spark to the coil and out the coil wire. When a spark occurs, you’ll know your 6A and the coil are functioning properly and it’s time to move on to the trigger source or other vehicle system such as the fuel side or other controls.


If you trigger the MSD through the 2-pin magnetic pickup harness, you’ll need a paperclip or a bare piece of wire. Disconnect the connector from the distributor and just like with the white wire, remove the coil wire from the distributor cap and position it about half-inch from ground. Without cranking the engine, turn the key to the on position then take the paperclip and short the violet wire to the green wire of the 2-pin connector over and over. A spark should jump when you remove the short.

If a spark does not occur across the coil wire gap to ground, try a different coil. Remember, the voltage from the MSD needs to go through the windings of the coil to build up a higher voltage so the coil could also be at fault. You can get away with swapping most any standard coil just to confirm this test.


If there is still no spark and all the connections and voltages check okay, the issue points at the MSD box and you should send the unit to the MSD Customer Support team. Remember, these units have a one year warranty, plus most of the 6A series can be rebuilt so it’s worth sending the unit in after you’ve taken the proper steps and checks.

Troubleshooting your MSD Ignition can easily be accomplished as explained earlier, but if you’re looking for a better way to confirm the operation of the coil, ignition and much more, MSD offers an easy to use hand held Ignition Tester. This Tester, PN 8998, simulates a trigger signal on the mag pickup or white wire of the MSD and has a digital read out allowing you to ‘control’ the rpm. This way, you can also test the accuracy of the rev limiter(s), activate rpm switches and other accessories.


The tester simply connects to a 12 volt source and ground plus is supplied with a clip-on test plug that puts a small load on the coil that connects to ground. It’s easy to use and very helpful when it comes to confirming the operation of the ignition system. 

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