capg

1984 Corvette - Chasing a no start condition... History - Car started missing and chugging, could only get a max 35 Mph out of it. Made it home but now it won't start. Noted weak yellow spark during trouble shooting. Tested Volts to dizzy = 12.4 on Ignition, 9.9 when cranking. Replaced ignition module and tested coil resistance = in spec. What else should I be looking at? Can spark control module cause this issue? Any other suggestions? ECM?? Thanks.

s carter

Control module's are for the most part a pass or fail not a weak spark thing, coils can test well on the low voltage tests but make you crazy on the road. Coils are not a very expensive on the Original Equipment level so a replacement cost is less painful than torment of is it good or not.

. Make sure if you do replace cap, coil and rotor that you bring over the ground bridge from old cap and replace center contact.

capg

Thanks for response. It's a DUI distributor. Coil primary was a tenth below spec, .3 ohm vs low end range of .4 ohm but my understanding is that would actually create more voltage/stronger spark. Dizzy doesn't have that many miles on it probably 6K at most. Also got a series of Malf Codes but I believe it was due to the poor running condition and not real defects one that lingered however was "51" Prom. I have a Dynamic EBL Flash II ECM installed and am now wondering if an ECM defect is influencing the weak spark. I know it sounds improbable but I have to ask.

stew86MCSS396

in my experience ICMs are all or nothing. Had a bad coil once that displayed rough running to the point the engine stalled. Pushed to the side of the road and restarted just fine. Drove a few miles and repeat. Finally dead about a mile from home...but as you mentioned coil is new. Plug wires???

What does BobR have to say about that code 51? I don't think an ECM would have any influence on a weak spark.

capg

Thanks... RBob, the go-to-guy on this stuff has me pretty much convinced it can't be the ECM and 99.99% of the time he's spot on. Plug wires in good shape. I broke down and ordered new ignition module, cap rotor and coil - all DUI stuff from Summit. Hope that does the trick - issues have been frustrating and not uncommon on my highly modified Crossfire. Seems like every time I'm close to that fire breathing tune something goes South - like this car is fighting me - a "Christine" candidate for sure.

capg

Just re-read your response.. Ground bridge and center contact? Can you elaborate on that? One of the standard connections? Thanks.

s carter

A common forgotten part that is left behind in the old cap is the ground bridge a stamped steel piece sits under the coil. In many cases people will open a pile of boxes to replace the cap & coil a lot of the time the bridge is not included or is just cheap tin that you look and say we're the Hell does go, the GM on is better in most cases. The contact most of the time the contact that do come with the cap are cheap.

stew86MCSS396

I'm a visual kinda guy... Would it even run with that piece missing???
https://www.corvetteforum.com/forums...stributor.html

s carter

Probably not if it did it wouldn't be well

capg

New DUI coil, cap, rotor, and ignition module from Summit did the trick... had it in a few days - fast. So, lessons learned??? Don't trust cheap chit ignition modules OR coils that test within spec. Ha. Nothing like the shotgun approach to fixing things - at least I saved shop fees!

htrdbmr

DUI strikes again. High priced cheap chit.

TommyFox

Supposed to be made in America. Junk. The DUI drop in replacement from Summit I got was a paper weight. DOA.....

capg

To the guys who posted negative comments on the DUI system - 1. It fixed the issue 2.Timing on your concerns are a bit late.