Vacuum Check your Optispark before Installation!
Thread Starter
Pro
Joined: Aug 2007
Posts: 668
Likes: 38
From: Austin TX
Vacuum Check your Optispark before Installation!
I have been having issues every time I hit a puddle, the 92 wants to drown out. After it sets for a while, it fires up. I first thought it was an issue with my knock sensors since they are the lowest electronic device in the front of the car that is connected to the ECM. The last time it happened, I threw a timing light on the car and noticed I was not getting spark from either the coil or the Optispark. Then it occurred to me that my Opti may be sucking water past the seal. I did a vacuum test on the unit and sure enough, it would not hold a vacuum. I spoke to technical support concerning this and they verified that the unit should hold a vacuum. Mine was leaking past the o-ring seal at the bottom but determined it also leaked significantly at the wiring harness pass through. I siliconed mine and was able to establish a consistent vacuum. I am just saying that this should be checked before you install an Optispark. The vent system does no good if it is sucking atmosphere and water into the unit.
Last edited by mixalive; Sep 10, 2019 at 10:04 AM.
Le Mans Master
Joined: Aug 2015
Posts: 6,090
Likes: 1,972
From: St. Charles MO
Bringing this back up to ask for clarification. I may be about to replace my opti, and I have a good OE (gently used) replacement to install. But the replacement does not hold a vacuum. So to fix that, did you just put silicone on the outside of the "seam," or did you remove the cap and put silicone in the mating edges?
Thread Starter
Pro
Joined: Aug 2007
Posts: 668
Likes: 38
From: Austin TX
Bringing this back up to ask for clarification. I may be about to replace my opti, and I have a good OE (gently used) replacement to install. But the replacement does not hold a vacuum. So to fix that, did you just put silicone on the outside of the "seam," or did you remove the cap and put silicone in the mating edges?
Le Mans Master
Joined: Aug 2015
Posts: 6,090
Likes: 1,972
From: St. Charles MO
Guys, mine was leaking at the wiring harness pass through. It has O-rings on main sealing surfaces for the cap and the plastic part underneath, but I went ahead and put a small bead of silicone on those surfaces.
But the wiring harness is really not sealed from the factory. It doesn't appear that they intended it to be sealed. As you noted, that's really just a pass-through for the plug to go into the sensor. So how did any of you manage to seal it with silicone? It looks to me like GM intended the waterproof seal on the plug itself to be the seal here.
But the wiring harness is really not sealed from the factory. It doesn't appear that they intended it to be sealed. As you noted, that's really just a pass-through for the plug to go into the sensor. So how did any of you manage to seal it with silicone? It looks to me like GM intended the waterproof seal on the plug itself to be the seal here.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Le Mans Master
Joined: Aug 2015
Posts: 6,090
Likes: 1,972
From: St. Charles MO
Correct, a factory part on a 96 vented opti. I could try to topically seal the harness pass-through, but the plug is so deep in there I think it would be really hard to get silicone where I want it and keep it out of areas I don't.
Thread Starter
Pro
Joined: Aug 2007
Posts: 668
Likes: 38
From: Austin TX
Be sure to vent the weep hole on the bottom of your water pump to below the opti so the water pump doesn't dump on the opti. Here is that link:
https://www.corvetteforum.com/forums...r-lt1-lt4.html