Holley Smart coils
Holley Smart coils So out of curiosity for those who have installed the Smart Coils, how critical is it that they're grounded directly to the battery?
I installed a set on my car, set the dwell and what not in the Holley EFI, but the car won't light off. When switching back to the OE coils it fires immediately.
I have the 'big wire' harness and both grounds going to separate points on each of their respective cylinder heads since the battery is remote mounted in the trunk... is relocating this ground that critical to get it to run, or am I facing a different issue here?
Any insight is appreciated!
I installed a set on my car, set the dwell and what not in the Holley EFI, but the car won't light off. When switching back to the OE coils it fires immediately.
I have the 'big wire' harness and both grounds going to separate points on each of their respective cylinder heads since the battery is remote mounted in the trunk... is relocating this ground that critical to get it to run, or am I facing a different issue here?
Any insight is appreciated!
TECH Regular
Joined: Jul 2019
Posts: 460
Likes: 44
I’ve never used coils but wiring wise, nothing should have to go back directly to the battery. As long as your battery has a big solid ground to the chassis, you will provide plenty of ground with a clean chassis where ever.
nice solid, clean ground strap to chassis/Trans/engine and battery, should provide you with solid ground anywhere you please after that.
nice solid, clean ground strap to chassis/Trans/engine and battery, should provide you with solid ground anywhere you please after that.
I have a 4/0 ground to the engine from the chassis, and a 4/0 ground from the battery to the chassis, again mounted in the trunk.
My multimeter shows the same impedance from 2 points on the same head as it does from the cylinder head to an OE ground point on the core support, which is <0.1 ohms.
Same measurements I get from the lead ground terminal to the sheet metal of the grounding point in the trunk.
It doesnt want to fire with the smart coils, but lights right off with the OE truck coils. Needless to say I'm confused.
My multimeter shows the same impedance from 2 points on the same head as it does from the cylinder head to an OE ground point on the core support, which is <0.1 ohms.
Same measurements I get from the lead ground terminal to the sheet metal of the grounding point in the trunk.
It doesnt want to fire with the smart coils, but lights right off with the OE truck coils. Needless to say I'm confused.
I’ve never used coils but wiring wise, nothing should have to go back directly to the battery. As long as your battery has a big solid ground to the chassis, you will provide plenty of ground with a clean chassis where ever.
nice solid, clean ground strap to chassis/Trans/engine and battery, should provide you with solid ground anywhere you please after that.
nice solid, clean ground strap to chassis/Trans/engine and battery, should provide you with solid ground anywhere you please after that.
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9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
So out of curiosity for those who have installed the Smart Coils, how critical is it that they're grounded directly to the battery?
I installed a set on my car, set the dwell and what not in the Holley EFI, but the car won't light off. When switching back to the OE coils it fires immediately.
I have the 'big wire' harness and both grounds going to separate points on each of their respective cylinder heads since the battery is remote mounted in the trunk... is relocating this ground that critical to get it to run, or am I facing a different issue here?
Any insight is appreciated!
I installed a set on my car, set the dwell and what not in the Holley EFI, but the car won't light off. When switching back to the OE coils it fires immediately.
I have the 'big wire' harness and both grounds going to separate points on each of their respective cylinder heads since the battery is remote mounted in the trunk... is relocating this ground that critical to get it to run, or am I facing a different issue here?
Any insight is appreciated!
You've done something wrong.
Let's face it , many will have rear mounted batteries, so the notion of having to wire direct to the battery is a little odd.
Mine certainly arent, and have been using them for 2+ years without issue.
Just make sure all terminations/connections are good and sound.
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Verdad Gallardo So I got sent out of town on business finally got a chance to sit down with a meter and check these things out.
I've found that Motion has the Pin C and Pin D tied together, a pair of coils in the harness is sent to Pin B thick gauge ground, and the other pair is sent to Pin C on the thick gauge ground sub-sub harness. I called Motion and they insist this is normal, and wired as expected; all the literature I've read from the OE's (Holley, AEM, Merc racing, etc) all insist those two grounds are supposed to be seperate, with the high current ground going to a strong battery-direct (not sheet metal?) ground point.
See the link for the harness I'm referencing.
https://www.motionraceworks.com/coll...-brackets-pair
Anyone have any insight on this aspect of it? I'm half tempted to just order the Holley (https://www.holley.com/products/igni.../parts/558-318) harness and see. I wish they included a wiring diagram on their website as to how they have theirs wired just to confirm. You'd think it would make more sense to leave the Odd and Even Bank's cylinder head reference ground (pin C) going thru the 7 pin metripak connector back into the LSx Main Harness rather than tying it into high current ground.
To make things more interesting, the coils are firing when I hook up a tester to the ignition wires. So apparently the timing with these coils is just waaaaaaay off somehow.
Again, if I unplug this harness and put the old D585 coils back it fires right up.
tl;dr the only deviation from the instructions is the pre-made harness has C & D tied together.
I've found that Motion has the Pin C and Pin D tied together, a pair of coils in the harness is sent to Pin B thick gauge ground, and the other pair is sent to Pin C on the thick gauge ground sub-sub harness. I called Motion and they insist this is normal, and wired as expected; all the literature I've read from the OE's (Holley, AEM, Merc racing, etc) all insist those two grounds are supposed to be seperate, with the high current ground going to a strong battery-direct (not sheet metal?) ground point.
See the link for the harness I'm referencing.
https://www.motionraceworks.com/coll...-brackets-pair
Anyone have any insight on this aspect of it? I'm half tempted to just order the Holley (https://www.holley.com/products/igni.../parts/558-318) harness and see. I wish they included a wiring diagram on their website as to how they have theirs wired just to confirm. You'd think it would make more sense to leave the Odd and Even Bank's cylinder head reference ground (pin C) going thru the 7 pin metripak connector back into the LSx Main Harness rather than tying it into high current ground.
To make things more interesting, the coils are firing when I hook up a tester to the ignition wires. So apparently the timing with these coils is just waaaaaaay off somehow.
Again, if I unplug this harness and put the old D585 coils back it fires right up.
tl;dr the only deviation from the instructions is the pre-made harness has C & D tied together.
Last edited by Silvrfsh; Oct 12, 2019 at 04:24 PM. Reason: Added info
So I got sent out of town on business finally got a chance to sit down with a meter and check these things out.
I've found that Motion has the Pin C and Pin D tied together, a pair of coils in the harness is sent to Pin B thick gauge ground, and the other pair is sent to Pin C on the thick gauge ground sub-sub harness. I called Motion and they insist this is normal, and wired as expected; all the literature I've read from the OE's (Holley, AEM, Merc racing, etc) all insist those two grounds are supposed to be seperate, with the high current ground going to a strong battery-direct (not sheet metal?) ground point.
See the link for the harness I'm referencing.
https://www.motionraceworks.com/coll...-brackets-pair
Anyone have any insight on this aspect of it? I'm half tempted to just order the Holley (https://www.holley.com/products/igni.../parts/558-318) harness and see. I wish they included a wiring diagram on their website as to how they have theirs wired just to confirm. You'd think it would make more sense to leave the Odd and Even Bank's cylinder head reference ground (pin C) going thru the 7 pin metripak connector back into the LSx Main Harness rather than tying it into high current ground.
To make things more interesting, the coils are firing when I hook up a tester to the ignition wires. So apparently the timing with these coils is just waaaaaaay off somehow.
Again, if I unplug this harness and put the old D585 coils back it fires right up.
tl;dr the only deviation from the instructions is the pre-made harness has C & D tied together.
I've found that Motion has the Pin C and Pin D tied together, a pair of coils in the harness is sent to Pin B thick gauge ground, and the other pair is sent to Pin C on the thick gauge ground sub-sub harness. I called Motion and they insist this is normal, and wired as expected; all the literature I've read from the OE's (Holley, AEM, Merc racing, etc) all insist those two grounds are supposed to be seperate, with the high current ground going to a strong battery-direct (not sheet metal?) ground point.
See the link for the harness I'm referencing.
https://www.motionraceworks.com/coll...-brackets-pair
Anyone have any insight on this aspect of it? I'm half tempted to just order the Holley (https://www.holley.com/products/igni.../parts/558-318) harness and see. I wish they included a wiring diagram on their website as to how they have theirs wired just to confirm. You'd think it would make more sense to leave the Odd and Even Bank's cylinder head reference ground (pin C) going thru the 7 pin metripak connector back into the LSx Main Harness rather than tying it into high current ground.
To make things more interesting, the coils are firing when I hook up a tester to the ignition wires. So apparently the timing with these coils is just waaaaaaay off somehow.
Again, if I unplug this harness and put the old D585 coils back it fires right up.
tl;dr the only deviation from the instructions is the pre-made harness has C & D tied together.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
It's not like there aren't dozens of wiring diagrams for these coils.
The cylinder head ground, pin C, is not a reference ground. It IS a power ground.
Pin B is the reference ground for the 5v trigger and is common and should go back to ecu sensor ground.
The cylinder head ground, pin C, is not a reference ground. It IS a power ground.
Pin B is the reference ground for the 5v trigger and is common and should go back to ecu sensor ground.
I don't know if they are or aren't a sponsor here. They're seem reputable, but they're insisting I did something wrong... which I can't seem to figure out what. Aside from the goofy wiring scheme of this specific harness I haven't had any issues with their other products.
If you read the instructions on the Holley website, it doesn't specify what kind of ground Pin C is specifically. But it does specify Pin D is a high current ground that needs to go to the battery. Either way, Pin C does go to the cylinder head to a dedicated ground point on the head (Ohms between the 3 pin connector and the cylinder head is .01Ohms (same reading I get when I short the leads together of the meter). The problem I see is that Pin D is also wired to go to this point as well, because that's how the harness was manufactured.
Last edited by Silvrfsh; Oct 13, 2019 at 08:05 PM.
Well, I said screw it and got the Holley harness and wallah, fired right up. Moral of the story, if the instructions say grounds should be separate.... the manufacturer should separate them.
