Problem With LS2 Ignition Coils

[LuckyX2]

Hey guys, I decided to swap to the GM LS2 truck coils because I was getting some spark blowout at higher boost. I spent the day yesterday wiring them up and mounting them but I'm getting a strange problem. When I go to start it, it cranks over but doesn't start. The strange part is that the second I turn the key off, there's a loud bang as the excess fuel ignites and shoots a fireball out my exhaust.

So basically it seems as if the coils aren't firing until the second I turn the car off...

I had started the car with the stock coils a few days before I put in the new ones so I know my Haltech ECU is set up correctly and the car is set to run fine. The only thing I've changed since then is the ignition coils, so that must be where the problem is.

How I wired the coils up is as follows: I took the four 12v+ lines, soldered them together and soldered them to a switched 12v+ source, took the four ground lines, soldered them together and attached them to ground on my intake manifold, took the four signal grounds, soldered them together and soldered that to the signal ground that was going into the igniter chip which I removed and lastly, soldered the four individual signal wires into their respective signal wire that was going into the igniter chip. The four wires coming out of the igniter chip are not being used now so I taped them off and the whole part of the harness connecting to the stock coils is removed and the plug taped off.

What could be going on? Is there something I need to change in the ECU settings besides setting the dwell to 5ms? I'm pretty certain the wiring is ok so I'm a little stumped.

Any suggestions would be greatly appreciated.

[LuckyX2]

Well I fixed it just by switching to a different 12v source. But now it's idling really rough haha. Always something...

[Blown240sx]

Ok your wiring sounds funny to me. You may have just explained it wrong or something but here is how I would run it. This is how we wired a set of MSD coils on an RB25.

I like to use a relay to ensure the power source is strong and not pulled by anything else. Run a power from the battery to the Relay then the output to the coils. That way its a direct link for the coils. 10 gauge wire would be best for good power source.

[Sil240]

ls2-truck-coil-swap-t478565.html

[Blown240sx]

ls2-truck-coil-swap-t478565.html

So the only thing else thats different than the MSD is that the coil has its own ground also. So Add a ground wire for that to the negative terminal of the battery.

I guess the MSD coils ground through their mounting spots.

[LuckyX2]

Blown240sx: I did wire it up like that, sorry if I wasn't clear. I got a little too wordy it seems. The only thing is that I'm not using a dedicated relay. I'm using what I believe to be the 12v signal from the stock ignition relay which also has my radiator fan pulling off of it. I could post up a picture of exactly what wire I'm talking about but it's the thicker gauge black wire with a red-ish/purple stripe on it that is coming from the blue relay attached to the chassis by the battery tray. Like I said, I could get a picture up here probably and that would make it clearer. Actually if anyone would like to post a picture of what wire to take the 12v from, that would be great.

Either way, it's running and I'm getting much stronger spark than before. I just need to tune my haltech now because it's giving it way too much fuel with the base map. It thinks I have the stock 370c's but I have 550cc's so it's keeping them open longer than needed and thus a rich condition and poor idle. 370/550 is .67 so I should just be able to multiply the entire fuel base map by .67 and that would give me a tune that would run like the base map but with 550cc injectors right?

Sil240: Thanks for your link, I actually have that bookmarked on a computer at work already haha, it was plenty help in my research phase of planning to do this. Thanks again.