Mandic

Lowest I have see is low 10V, I will have to watch again. I am most curious what the voltage at the Opti, Coil, and ICM are during cranking.

Battery is up front grounded direct to frame, with another cable attached to that ground and direct to the block. I am a fanatic about grounding FI engines. This motor has 4 separate grounds(1 to battery neg cable, one to frame, and 2 to body). Power is distributed from a junction block on the passenger side(battery is on driver's side). Main power and ground with 0ga cable.

The oddest thing about all of this, isn't the hard start, it is that after it does start everything is fine. Maybe the next start will be a tiny bit hard, but not anything unacceptable for a swapped car. Today I tweaked the tune(for the new fuel pressure) and then tweaked it again to try and balance the split BLM. Let the car sit with key on for a good 10-15 minutes, but not running. It fired right back up without skipping a beat.

Oh and battery is a brand new Red Top Optima.

Mandic

The one thing I can say is the power pickup for the Street and Performance harness is designed to be off the Battery terminal on the Starter. I don't care for that, but it is how it is currently hooked up. If I find I am not loving the voltage in the ignition system tomorrow I think I will relocate that to the Battery Junction Block where the main power feed is coming from. It is only a single 0ga wire away from that block now, but I'd far rather see it closer to the battery and not AT the point of the voltage draw(the starter). I don't love using Starters as junction points, but a lot of aftermarket harnesses seem to love it.

Ed Wright

iTrader: (1)

Low tens is too low. I would be doing some voltage drop tests. Even a new cable could have a terminal not making good connection. Put a volt meter on the battery for a cold start. If low there you have a battery problem. If OZkbthete you have a cable or wiring issue.

Mandic

About 11v at the battery cranking, 10.75v at the coil and ICM. So I'd like to see more but don't think that is the issue.

I just hooked up my scope real quick and started playing with it a bit. I just got this new one last week so not 100% I have it setup right, but pretty sure I do.

I am getting a fairly hashy 12kv ignition spike out of the coil consistently. So that seems a hair weak but I am picking up through an 8.5mm wire, so that could be playing a role. AT the #1 cylinder I am getting less than a 3kv spike. Somewhere in the Opti I am losing a LOT of spark energy. About to call MSD and run it by them.

Mandic

MSD Tech was useless. "Try a different coil." Rattled off my ignition numbers from the scope and didn't get much response, just "yea try a stock coil." Helpful.

95blackm6

My tuner told me that Bosch O2's do not work properly for LT1's, he said to only use AC Delco, Delphi or Denso.... I just put brand new Denso's in mine, so we'll see if it makes a difference.

Ed Wright

iTrader: (1)

I have found MSD tech about useless.

If you are talking about start up, O2 sensors have zero to do with start up, or voltage levels.

95blackm6

Ed, I understand it wont solve his cold start or voltage issue, I wasnt sure if it might help his split BLM's or not. Thank you for clarifying.

Mandic

I've never had trouble with Bosch O2s. Except that Bosch sells those JUNK "Universal" O2s that come with a flying lead and you are supposed to pin them to the specific cars connector. I have had some serious drivability issues that were fixed by replacing those. Heck I've replaced them with the specific fit Bosch unit and it worked fine.

Mandic

Swapped to a factory LT1 coil. Fired up nicely. Let it sit for about 3 or 4 hours, tried it, fired right up. Going to cold soak overnight again and see how it is. I really am starting to dislike MSD. Had a 6AL box die last week on a big project and now this damn near brand new coil.

BALLSS

Mandic

MSD=Must Suddenly Die

FWIW I chased more parts than I care to admit on a high rpm stumble when I had a new motor AND a MSD Opti.

BTW Ed, IMHO, is without a doubt the best at tuning these LTx motors so I would follow his advice

in the end it was a bad "new" MSD opti. After changeing every ignition part, valve springs, swaping injectors...put in my "old" GM opti and all has been fine since. MSD cap and rotor are good replacements for GM opti if needed....their opti's themselves I had no luck with.

O2's, many feel the only ones to use are the AC Delco's

If you have a GM/AC Delco/Delphi opti I would put it in to rule out Opti as being the problem to some of your issues.

Mandic

Sure as hell, it fired up like a champ this morning. That is after I removed the MSD coil and put on a factory one yesterday. Let it sit overnight in upper 40 degree weather, fired up within a few cranks, very acceptable. So looks like that MSD coil is shot.

Ed Wright

iTrader: (1)

You may not have heard what MSD stands for: Must Soon Die.
Guys say "You guys all have their stuff on your race cars."
Yeah, and we all carry plenty of spares. If somebody made comparable components that were more reliable, most would use them.
Go by the MSD trailer in the pits at a big race on the first day, check out all the racers there for parts testing & replacing. And, we don't put any miles on our stuff. I would never use any of it on my street car.

quik95lt1

iTrader: (7)

ive been pretty lucky with msd stuff for the most part never had a huge failure but again i dont street drive much at all and i dont race nearly as much as ed.....i race maybe twice a month in the summer fall months.......ive busted two of their coils thats about it......but over 5 years