onetype

iTrader: (6)

Working on an Fbody with an LT 383. Motor was built by Calvin Automotive like 12 years ago.

Has a long crank time, buddy said it started doing it recently. Car sat for like 10 years, then he bought it back.

Checked for spark today both at the plug and from the coil and has no spark initially for at least 5 secs, then sparks, then fires.

Car has an MSD 6A in it.

Could it be the pigtail to the opti? Maybe the MSD is taking a ****?

Curious if anyone has had this problem.

96capricemgr

iTrader: (1)

would start by bypassing the MSD

onetype

iTrader: (6)

Yeah, just ran out of time today at the shop.

That's my first plan, just don't normally work on LT's with opti.

onetype

iTrader: (6)

Update:

Swapped in a stock ICM/Coil and same issue. MSD tested good.

Even ran the signal wire from coil directly to battery and same issue.

Car will fire and run fine, but doesn't get spark for 10secs or so.

PCM?

The only other thing I noticed which I thought was odd was the coil signal wire (keyed 12v) is getting 12v with ignition on, but when you actually crank it loses voltage. I thought maybe ignition switch going bad, but I tied into 12v constant and no change.

diaz90220

change the opti spark.

onetype

iTrader: (6)

Opti's either work or they don't. Plus, this condition is pre opti (coil wire), so this comment is rather absurd.

shbox

What do you mean? The coil won't fire, unless the opti tells the computer to tell the ICM.

Have you checked to see if the signals from the PCM to the ICM are being lost during this time of no spark?

Have you checked for any trouble codes? Some codes pertaining to the opti and ignition system don't light the check engine light.

How was the MSD 6A tested as good? Did you try completely bypassing it as 96capricemgr suggested?

onetype

iTrader: (6)

Not to be a dick, but if you had read what I posted you would have read that I checked it (using MSD's own methods), as well as swapping in a stock ICM/Coil from a good running LT1 and same issue.

It's a 383 there are several CEL's already.

As I stated, I'm not opti expert, but in my experience, they either work or don't.

96capricemgr

iTrader: (1)

Did you try without the MSD?

It isn't helping and there is still some chance it is a problem.

onetype

iTrader: (6)

Yes, for the 3rd time. I completely bypassed the MSD.

However, as I stated quite some time ago, the MSD tested perfectly fine.

Can we move on from the MSD? Thanks.

Not trying to be a dick, but asking the same questions I already answered doesn't help

96capricemgr

iTrader: (1)

Please quote the exact posts where you said you bypassed the MSD? It does nothing for an NA 383 but complicate the system and create another failure point

Optis are not necessarily black and white good or bad. They are also not a bad design if handled competently.

Figure out the CELs and clean all the grounds, consider adding larger gauge wiring to grounds.

You said there are several CEL's what are they?

Far as your attitude, keep it up and the knowledgeable folks who could actually help you like shbox and I are going to stop trying and you will be left with people who will chant opti or blindly agree with whatever you say and not be of any actual help.

shbox

I read what you posted. It said nothing other than "MSD tested good" - no other details. That is why I asked the question.

You did not address any of the other questions I asked. Oh, well. Good luck.

ahritchie

iTrader: (1)

^Agreed, you are certainly no opti expert with a statement like that. Yes, there are many shades of grey of opti related issues beyond complete failure. Random misfires, hard starts, ect....

Also, "several CELs already" doesn't answer the question.....

bufmatmuslepants

iTrader: (3)

Grounds is a good place to start.