Yet another MSD crank trigger wiring question

[Rob Petrie E395]

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.

[pmrphil]

swap the wires, check the timing, and then you'll have that answer, at least.

[Robin Lawrence]

There are a few possibilities here.

I am not a fan of the 2 wire magnetic crank sensor when triggering the Holley EFI.
I assume that you are running the timing through the Holley HP ECU.

I prefer the Holley 554-118 Hall Effect Sensor. It uses the same 4X Wheel and Bracket that you already have from MSD.

In the ignition configuration I would look at the settings for the crank sensor and the output to trigger the MSD box. The default signal output is 1.5ms. I have seen boxes that wanted more dwell time for the MSD box to trigger properly. Try 5ms and then 9ms if the 5 doesn't work.
Be sure that the crank sensor if setup to magnetic with the 2 wire MSD sensor and not digital.

Does this engine use a Cam sensor?

Robin

[Adger Smith]

Do you run an electric water pump?
I had a pump go bad(Leak) at a race. I had a spare in the trailer. No issue because I had time to change between rounds.
Next round I had a hi RPM stutter show up..
Changed the crank trigger pick up. Stutter is still there.
Sat there in the pits and thought the problem through.
Next round I kept the pump on during burn out and turned it off as I staged.
No miss that run.
When I got home I put a seal in the first pump and put it back on the car.
No miss next time I ran the car.
My conclusion is the pump was a radio station that produced RFI that interferes with the MSD. Probably the pickup since my V-6 uses a cam trigger and close to the pump.

[Dirk Olson]

May be out in left field here but sounds like a noise issue? check your grounds.

Dirk

[Joe Schweigert]

Do you have a TPS ? I also had a similar issue with a Holly System Probably not the crank trigger

[Rob Petrie E395]

It is a 93-97 LT1 Firebird so no cam sensor. Right now, it still has the Commander 950 Pro FI system in it. Yes timing through the C950. But I have the Holley HP system here now. Hopefully within the next couple weeks I can start installing it. Going to order the 554-118 Hull effect crank trigger you suggested and the 558-431 Cam/Crank harness unless you have a better suggestion. I see they say to use the 558-306 universal harness. I don't see a harness that is just for the Hull Effect Crank Trigger. Unless I buy the universal unterminated 306 Harness and make one. Will it hurt anything to use the 431 and just leave the cam sensor connector tied back out of the way?

Originally Posted by Robin Lawrence

There are a few possibilities here.

I am not a fan of the 2 wire magnetic crank sensor when triggering the Holley EFI.
I assume that you are running the timing through the Holley HP ECU.

I prefer the Holley 554-118 Hall Effect Sensor. It uses the same 4X Wheel and Bracket that you already have from MSD.

In the ignition configuration I would look at the settings for the crank sensor and the output to trigger the MSD box. The default signal output is 1.5ms. I have seen boxes that wanted more dwell time for the MSD box to trigger properly. Try 5ms and then 9ms if the 5 doesn't work.
Be sure that the crank sensor if setup to magnetic with the 2 wire MSD sensor and not digital.

Does this engine use a Cam sensor?

Robin

[Rob Petrie E395]

I think I posted about this problem several years ago. And you had told me about the water pump EMI back then. So I tried that by putting the water pump on its own switch. Didn't help. But it was worth a try. Thank you for the suggestion. I'm leaning towards a EMI problem. Just have not found it. Hoping when I rewire the car this time for the new HP system I find the problem.

Originally Posted by Adger Smith

Do you run an electric water pump?
I had a pump go bad(Leak) at a race. I had a spare in the trailer. No issue because I had time to change between rounds.
Next round I had a hi RPM stutter show up..
Changed the crank trigger pick up. Stutter is still there.
Sat there in the pits and thought the problem through.
Next round I kept the pump on during burn out and turned it off as I staged.
No miss that run.
When I got home I put a seal in the first pump and put it back on the car.
No miss next time I ran the car.
My conclusion is the pump was a radio station that produced RFI that interferes with the MSD. Probably the pickup since my V-6 uses a cam trigger and close to the pump.

[Rob Petrie E395]

Originally Posted by Dirk Olson

May be out in left field here but sounds like a noise issue? check your grounds.

Dirk

I'm thinking that too. I suspect since the MSD box and the FI ECM are both inside the car on the passenger floorboard. Thats got something to do with it. Because the crank trigger is on the left side of the engine. And the coil is on the front of the Left Cyl head. Don't know if the wires are just too long. Or if the long coil wires are causing noise and messing up the crank signal. I can't data log it. Because my data logger is part of my FI. And it does it when it first starts. Any ways I'm making a ton of changes to the engine. So it'll require tuning. Rather than keep fighting the C950. I figured I'd just make the switch now and redo all the wiring. And hope I find the problem.

[Rob Petrie E395]

Originally Posted by Joe Schweigert

Do you have a TPS ? I also had a similar issue with a Holly System Probably not the crank trigger

Yes on TPS. Its a GM TPS sensor. Same one GM used when these cars were built. I'll look at it before I tear the C950 out. And see if its acting unusual. But don't remember seeing anything on data logs in the past.