MSD No Spark Intermittent fault Issue.

[Shep69 149]

So I went to start the motor today and it wouldn't start. Checked for fuel and it was all good. Checked spark and nothing. Im running a MSD pro billet dizzy with a MSD 6A box. I changed out the magnetic pickup in the dizzy about 6 months back when I found it a bit rusty . So I  changed the coil and no go. The funny thing is if i do the paperclip test on the trigger plug i have spark. As soon as i plug the coil lead and trigger wire back  in the motor starts first turn.  This is an intermittent fault and has just started . Sometimes it starts and sometimes it doesn't.  Anyone have any other ideas . Could the 6A box be on its way out . Its probably about 12 years old but hasn't had much use from new.  TIA

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[Mach1 Driver 560]

As I'm sure you know by now, intermittent problems are the worst sort of problem to fix. Check the circuit for good connections (including grounds) and as a last resort start replacing parts.

[1969_Mach1 333]

I think Mach1 Driver is right.  Your options will probably come down to try another pick up coil, if that doesn't fix it, then another ignition box.  If when there is no spark and you immediately do the paperclip test and that triggers the MSD box, I'd suspect the magnetic pick up again.

I've been using the MSD 6ALN with good luck.  It's basically a more robust version of the 6AL.  Performance is the same as a 6A or 6AL, just built more robust for dirt circle track racing.  They're more expensive so wait for a sale if you can.  I recently purchased another one for another project.  At least the 6ALN doesn't have a label anywhere that indicates made in China.

[danno 128]

Coils are a likely place for intermittent problems. It sounds like you changed the coil, though. If you changed the coil and the problem still happens, then the second chance is the wires going to the coil.  One idea is to install a test wire from the coil to inside of the car. Monitor the voltage on the coil with a voltmeter.  See what the voltage is when the car runs, and see what it is when the car does not work. 

The paper clip trick works well, but it is a simple test of the system for a very short period of time.  When the coil fires 4000 times  a minute, it will heat up and react differently. 

[Shep69 149]

Thanks for the tips guys. 

I can definitely rule out the coil as the new one still didn’t have spark when fault finding. Both coils also test ok using a multimeter. 

I pulled the dizzy cap and double checked the magnetic pickup gap and it’s all good. Rotor to cap gap it good. 

Funny thing is I started the motor on the weekend about 6 times and it fired up first crank so the saga continues. If it does it again I’m just going to start replacing parts starting with the magnetic pickup . 

[Mystang 11]

   Usually it will be the pick-up. I've had the same thing happen to me a couple times over the years. The last time was on my 69 convert. Brand new dizzy, ran fine for a few months. Then it would start and run fine till it warmed-up under the hood (not over heated) and it would die and not start until it cooled off. 

   Now I keep a replacement dizzy in the garage. (Plug and play) I also have an extra coil, but I would start with the pick-up/distributor every time.

[Shep69 149]

Is there any way you can test the magnetic pickup with a multi meter?

[1969_Mach1 333]

On 2/22/2020 at 5:37 PM, Shep69 said:

Is there any way you can test the magnetic pickup with a multi meter?

Yes, you can check the resistance in the magnetic pickup using an ohm meter.  If MSD doesn't list values for the correct range you can search for that information for a Ford magnetic pickup used in Duraspark ignitions during the 1970's.  I think the MSD magnetic pickup is a Ford style.  At least that's what it looks like.