Any way to trigger a MSD CD?

[tomeric914]

I searched but could not find...

Is there a way to trigger a MSD 6A using output direct from a '79 SC distributor? Someone's had to have done this already.

Also need a way to check and see if the hall effect sensor even works in the distributor I have. Is there a simple way without having a distributor test setup?


thanks!

[TimT]

Yes, it can be done. My cars are hibernating now, and I don't recall exactly how to wire it..so I can't easily check the wiring

[James Brown]

I don't get the question, OF COURSE a SC distributor will trigger a MSD or stock ignition system. Do you have the instillation instructions from MSD? if not go to there website and download a copy. Don't use the white wires.

[James Brown]

wiring diagram for your approval.

[tomeric914]

Naw, it can't be that easy. It's not a magnetic pickup.

This was what was posted on the MSD forum:

“Unfortunately Hall effect signals will not trigger an MSD Box. However if your VW is an old air-cooled model you can replace the stock distributor with an MSD Distributor, PN 8485. This will allow you to use an MSD Ignition System because the MSD Distributor uses a magnetic pickup system.”

[RoninLB]

MSD 6AL How to wire

[TimT]

Naw, it can't be that easy.

Actually it is...

That wiring diagram sparked my memory, and yes the SC dizzy on my 3.2 in the 914 is connected in that fashion..

[tomeric914]

Thanks! Finally an easy solution!

Is there a way to test the distributor to make sure the Hall effect sensor is good?

[Steve@Rennsport]

FYI,...SC distributors use magnetic triggers,....

I use my Sun 504 distributor machine to check these things.

[tomeric914]

Bad assumption on my part. Thanks for the clarification!

[Eagledriver]

The green and purple pair on the MSD are the trigger wires. The green goes to the green on the dizzy and the purple goes on the braided shielding of the green wire on the dizzy. You can check the magnetic trigger a couple of ways. Hook up an analog volt meter on a sensitive setting (1 volt or so). Rotate the dizzy and you'll see the needle move back and forth on the meter. Also can check the resistance on the trigger. A good trigger will have low resistance and a bad one will have vitually infinit resistance (open circuit).

-Andy

[tomeric914]

Thanks Andy. Easy enough to do as a high level check.

[whiteSC]

Greetings all. I’m grappling with a no spark issue on my 83 SC, which no longer starts. This seems to be the perfect thread to jump in with my first post on Pelican.

While the factory CD box still emits its signature whine, no spark jumps from the disconnected distributor center wire to ground while cranking. Replaced the cap, rotor, coil and braided plug wires. Pulled the plugs and found them all dry and light brownish. Both the old and new stock Bosch coils ohm tested within the range spec’d in Bentley. With 101 Projects book in hand, I decided now was a good time to try the MSD 6AL and blaster coil conversion.

Got a nice spark from the coil wire doing the test in the MSD instructions, by making and breaking the purple and green wires. That tells me the MSD box and coil are good. I then put the MSD trigger wires into the disconnected plug from the factory CD box using male terminals per Fred Cook’s method in the above “How to wire” thread, green to factory green (terminal 7) and purple to shield (T 31d). Again no spark from the coil while cranking.

The resistance between those two terminals is about 550 ohms. Andy, is that in the ballpark for low? Regarding the voltage check for the trigger, is measuring it by cranking the engine with the distributor in place ok, versus pulling it and spinning it by hand?

Would the next step be trying to locate a spare distributor from somewhere to see if my magnetic trigger is the problem?

Regards, Jeff

[James Brown]

Jeff, welcome-make a formal "new guy" post on the forum. Sounds like the CD unit is not receiving the signal from the dissy. check the green wire at the CD unit with a multimeter while cranking the engine and see if there is a signal from the coil inside the dissy (it's micro voltage). Ohm out the green wire to make sure there is no opens in the wire. You can get a new dissy pick-up from any NAPA if there is no signal from the dissy. Not a cheap wire, but cheaper than a MSD unit. Better check in with us prior to doing any "fixen".

[Pazuzu]

Originally Posted by whiteSC

Got a nice spark from the coil wire doing the test in the MSD instructions, by making and breaking the purple and green wires. That tells me the MSD box and coil are good. I then put the MSD trigger wires into the disconnected plug from the factory CD box using male terminals per Fred Cook’s method in the above “How to wire” thread, green to factory green (terminal 7) and purple to shield (T 31d). Again no spark from the coil while cranking.
The resistance between those two terminals is about 550 ohms. Andy, is that in the ballpark for low? Regarding the voltage check for the trigger, is measuring it by cranking the engine with the distributor in place ok, versus pulling it and spinning it by hand?

The green wire should be around 600 ohms across the terminals, so 550 is appropriate. However, the wire is sensitive. Put the ohmmeter back on it, and then wiggle the wire all around to see if there's a crack somewhere. It would change the way the engine runs based on temp, vibration, etc.

So, your coil and MSD (and presumably your CD box) all work, as you thought. The Green Wire is at least somewhat stable from your measurements. Next step is to pull the dizzy (not hard at all). Then, you can check the Green Wire connector to the dizzy (which gets very very brittle, be careful). If that checks out, then you can go to a full system check:

Dizzy pulled out. You don't need the cap, rotor or any sparkplug wires. MSD wired. Take a plug wire and go from the coil to a sparkplug directly, ground the side of the sparkplug.

Now, you can manually rotate the dizzy via the bottom gear, and see if you get 6 clean sparks per rotation. You can really tell if it's sparking 6 times, and how cleanly this way. If you have an intermittent short in the green wire, this is a great way to check it out in action.

[whiteSC]

JB and Mike : thanks for the guidance on checking the green wire etc. I'll try the half in situ/half bench test - a very cool idea. The brittleness of that plastic connector that's been cooking in the engine bay for the last 27 yrs will be minded.
Jeff