Yet another MSD crank trigger wiring question

Rob Petrie E395 · 02-12-2024, 11:07 AM

Rather than mess up the other MSD post about which way to wire the crank trigger. I figured I’d start another. Because my question is more specific to my junk. And a problem I’m having.

Assuming in the previously posted scenario a MSD crank trigger is being used directly on a MSD box. But if the crank trigger is wired to a fuel injection system which is then controlling and firing the ignition. Do we still need to do this (Checking wired both ways)?I would guess so. But I had never heard of this until just now. I always just wired it according to the wiring diagrams and the colors they show on the wires. What happens if it’s backwards but timing shows right? I guess what I’m asking is what happens if it’s backwards showing less timing. But you just advanced the timing so it shows right because you didn’t know this was a thing. And is it still
A thing if the MSD is being triggered by the FI system.

Reason I ask all this. Is because I’ve got this weird thing going on. Where about 1 out of 20 times I start the car. It sounds like it’s firing every cylinder at once, really rough idle and will pop back through the throttle body if you try to push the accelerator. But click it off and immediately fire it back up. And it’s fine again. I’ve changed EVERYTHING! ECM (3) FI wiring harness (2) rewired most of the car, new coil, new crank trigger everything. Now I’m now switching from Commander 950 to a HP system. Only thing that has made a difference was the MSD box. I put one in that PAT modified. And it’s gone from once every 5-10 times to once every 20 times. It’s not the end of the world. But it effs with my concentration if it does it right before an elimination run. I go from calm to Oh S! And it gets my heart racing. And I can’t concentrate like I need to and I make stupid mistakes. Been fighting it since the car was first put together. Thought I had it fixed when I swapped boxes and it went so much longer between doing it. I don’t know what’s up. But just learned this is a thing. So it’s something else to try I guess. If it’s not this. It’s gotta be some kind of EMI problem. But this car is wired and wires routed the exact same way as another car I own (bracket car) With the exact same components. (So in a emergency I can swap parts quickly and easily) And it’s been fine for over 20 years. Very frustrating to say the least.

02-12-2024, 11:07 AM	#1
Rob Petrie E395 VIP Member Join Date: Dec 2007 Location: Woodlawn IL Posts: 1,092 Likes: 162 Liked 216 Times in 77 Posts	Yet another MSD crank trigger wiring question Rather than mess up the other MSD post about which way to wire the crank trigger. I figured I’d start another. Because my question is more specific to my junk. And a problem I’m having. Assuming in the previously posted scenario a MSD crank trigger is being used directly on a MSD box. But if the crank trigger is wired to a fuel injection system which is then controlling and firing the ignition. Do we still need to do this (Checking wired both ways)?I would guess so. But I had never heard of this until just now. I always just wired it according to the wiring diagrams and the colors they show on the wires. What happens if it’s backwards but timing shows right? I guess what I’m asking is what happens if it’s backwards showing less timing. But you just advanced the timing so it shows right because you didn’t know this was a thing. And is it still A thing if the MSD is being triggered by the FI system. Reason I ask all this. Is because I’ve got this weird thing going on. Where about 1 out of 20 times I start the car. It sounds like it’s firing every cylinder at once, really rough idle and will pop back through the throttle body if you try to push the accelerator. But click it off and immediately fire it back up. And it’s fine again. I’ve changed EVERYTHING! ECM (3) FI wiring harness (2) rewired most of the car, new coil, new crank trigger everything. Now I’m now switching from Commander 950 to a HP system. Only thing that has made a difference was the MSD box. I put one in that PAT modified. And it’s gone from once every 5-10 times to once every 20 times. It’s not the end of the world. But it effs with my concentration if it does it right before an elimination run. I go from calm to Oh S! And it gets my heart racing. And I can’t concentrate like I need to and I make stupid mistakes. Been fighting it since the car was first put together. Thought I had it fixed when I swapped boxes and it went so much longer between doing it. I don’t know what’s up. But just learned this is a thing. So it’s something else to try I guess. If it’s not this. It’s gotta be some kind of EMI problem. But this car is wired and wires routed the exact same way as another car I own (bracket car) With the exact same components. (So in a emergency I can swap parts quickly and easily) And it’s been fine for over 20 years. Very frustrating to say the least.