I have this odd issue and I think it's probably ignition related. It's an LT1 with an MSD-6AL and perhaps the MSD is the problem. I have once heard an electrical shorting noise when cranking the engine and it didn't sound good, but only once, and the symptoms were the same before and after the offending noise.

Other background and symptoms: The car usually starts up just fine cold (sometimes requires two attempts). It runs fine once started and will run all day without any issues or symptoms. If you shut it off it won't restart. It will crank and start to fire but just sputter briefly and then that's it ...you're in for a wait, it will just crank and crank and not fire (fuel pressure looks ok as it does this). It has to cool down for like a half hour before it will re-start ....then it will re-start just fine and run all day again (until you shut it off). It has the extra inline fuel pump that came with the Powerdyne kit and it's been on there for 15K miles. I have a fuel pressure gauge permanently mounted and it appears to be just like normal (but maybe I'm not paying enough attention to how it bleeds down after the key has been turned on). I have already swapped the MSD Blaster coil for my stocker and it made no difference. I have checked wiring for frays and found nothing. I cannot see anything happening while it runs in the dark, looks normal. I want to bypass the MSD to see if that cures it but the guy who wired my MSD did it a little differently from the directions, I can't figure out how to bypass it. I've run the MSD for at least 10K without any issue yet (unless it is the issue here).

So ....any of this sound familiar? If anyone has any ideas let me know please, thanks.

 

your post almost tells you how to fix it. If you run all day long with no problems untill you shut it down by then it is hot, then when it cools it works again. right there. Were do you have it mounted? is it close to your exhaust? or real close to the engine? move it away to like the fire wall. or just move it away from anything hot. If it still keeps doing it it very well could be a bad unit, no matter how new it is.

 

Any codes? May involve heat soak of the IC Module or the optical cam position sensor in the Opti.

 

The opti is a newer vented unit, I kind of doubt it's the issue (has 7K miles and never sees water, this is a fair weather weekend car). Sorry but, what's the "IC Module"? ...you mean IAC module or something else? No DTC's at all.

kd5icr, I've been using this MSD mounted under the fuse box where the stock intake used to be for years ...never had an issue. The MSD is nearly 10 years old but only has about 15K miles. I read posts years ago that said the MSD6AL only lasts about a year before going bad (15K miles would represent a year of driving). I have to bypass the MSD first ....how to do it is perplexing to me but maybe my mechanic friend can figure it out.

Thanks for the input guys, if anyone else has some ideas chime in.

 

Ignition Control Module. It's mounted above the coil on a stock setup.

 

What brand is the Opti? The optical sensor modules in the aftermarket imports are notorious for premature failure. Has nothing to do with the Opti "never see(ing) water" - the electronic module breaks down when it overheats.

Shoebox to the rescue:

http://shbox.com/1/coil_loc.jpg

 

Thanks, I hadn't even thought of the ICM. I bought my Opti from Dal Slabaugh so it's OEM. My ICM is the original though. I see in that picture only one plug is in the coil. With my MSD setup there are two plugs in the coil, maybe it's as simple as unplugging one of them (to bypass it) ...I have no clue, it's a maze of wiring that I can't wrap my head around. For now the car is sitting garaged until my mechanic friend isn't so busy, then he'll look at it. What I don't get about possible heat soak is this: Why does it only keep it from re-starting warm? ....you can run it hard/hot all day long and it doesn't have a problem until you turn off the key and try to re-start it.

 

Make sure your MSD box does not have any butt or spade connectors on the wire harness....if you get much resistance fron the connectors the MSD box will shut down

 

Thanks for the tip. I have bypassed the MSD and it seems to no longer have the problem. I notice on the main connector for the MSD it is "gunky" on the inside (like old dialectric grease that's dried up?) and wonder if that's the issue. Wouldn't it just shut down any old time if the connectors were an issue though? It's only at the time of a warmed up restart that it won't fire ....pull wire off coil and no fire so it's not fuel related (at least I know that for sure now). Definitely seems to be related to the MSD somehow. It is almost 10 years old but has maybe 6K miles on it. I don't know much about ignition and connectors but I think it has some of the kind you're talking about ...so it could have contributed. Thanks again. Maybe by Spring I'll know what was wrong...just not using the car now ...brrrr.