No Spark with MSD

[rheng]

The car in question is a 1971 240z with a 280z engine and 280zx distributor.

 

I'm currently having some issues getting spark from my 6A MSD. At one point, the car did run fine with this exact setup and wiring shown in the attachment to this post (and here: https://www.classiczcars.com/uploads/monthly_2016_10/1918msd_zx_240z_1r2.jpg.9235e4af03e7d71e6584ff639ad81311.jpg) . However, the car currently isn't starting with this configuration. I was having some stuttering issues in the past, and the last two times I took the car out, it died and had to get towed home.

 

The car seems to run fine if I bypass MSD entirely and wire the ignition module and tach directly to the coil. With the MSD, I do not get spark from the coil. I have a brand new cap, rotor, ignition module, and wires installed. 

Here's where I am currently at with my troubleshooting:

- I am able to get spark from the coil wire when doing the green/purple and white wire test indicated in the MSD manual (see below). I think this suggests that the MSD is wired correctly and is capable of firing.

- New MSD. Did not work. I replaced with a 6AL and did not get a flashing LED when cranking. So, it doesn't look like the MSD is picking up any signal from the ignition module. This also came with a new wiring harness, so I'm thinking all the wiring should be good.

- Replaced ignition module. Didn't seem to help.

- Bypassing the MSD. Car starts and runs just fine.

- Bypassing the tach adapter. Still no spark.

- Directly wiring the B/W wire from MSD to the battery to eliminate the possibility of the ignition switch causing any issues. No spark. Its also worth noting that I have confirmed that, when the MSD is wired as shown in the diagram (ie not directly wired to the battery as previously mentioned), this connection sees 12V when switched on and around 9.6v - 9.8v when cranking.  

 

Running out of ideas here, so I'm hoping someone here can help me out!

 

 

MSD Manual test procedure: https://www.jegs.com/InstallationInstructions/100/121/121-6425.pdf

 

[NewZed]

13 hours ago, rheng said:

However, the car currently isn't starting with this configuration. I was having some stuttering issues in the past, and the last two times I took the car out, it died and had to get towed home.

 

Can't tell if you tried all of the different options after it finally quit starting or after the starting, running, then dying.  But the starting, running, then dying suggests that something is overheating.  Coils can overheat and go open circuit, and I think that the MSD boxes put more load on the coil with the multiple sparks.

 

Anyway,  try a new coil.  I didn't see that in your list.  Edit - actually, use a meter and check the coil's properties if you have one.  But, even then, it might be overheating as soon as it sees current.  A coil swap is probably worthwhile.

Edited September 12, 2020 by NewZed

[rheng]

On 9/12/2020 at 10:17 AM, NewZed said:

 

Can't tell if you tried all of the different options after it finally quit starting or after the starting, running, then dying.  But the starting, running, then dying suggests that something is overheating.  Coils can overheat and go open circuit, and I think that the MSD boxes put more load on the coil with the multiple sparks.

 

Anyway,  try a new coil.  I didn't see that in your list.  Edit - actually, use a meter and check the coil's properties if you have one.  But, even then, it might be overheating as soon as it sees current.  A coil swap is probably worthwhile.

 

So, the coil appears to be in line with the manufacturer specs for resistance. Also, the car seems to run fine if I directly wire the ignition module to coil. 

 

Based on this, I'm thinking the coil is probably okay, but I might try replacing it just to be sure?

 

To clarify, the bullet point troubleshooting items occurred after the car started and then died. Here's the series of events:

• Car was running but stuttering at higher revs. After about 45 min of driving, it died and wouldn't start. Started the next morning, but I didn't drive it around.
• Replaced carb jets and confirmed adequate fuel pressure to the carbs (initially, I though this was a fuel issue). Drove it for about 15 min, but then died and again and wouldn't restart. Same as previous bullet point.
• Replaced cap, rotor, and wires. Original cap that was replaced had visible signs of the rotor rubbing on the sides. Started for a couple minutes and then died. 
• Started troubleshooting with the items listed in my original post. 

 

 

Edited September 16, 2020 by rheng