Definitely a case of; "Your killing me Smalls!" 
Photography by J.G. Pasterjak
Having solved our C5 Corvette’s most recent issue–a faulty throttle body causing the ECU to freak out and go into limp mode–we thought we were back to having a 100% reliable Corvette.
“Thought” being the operative word there.
A few days after we had the throttle body issue solved, we suddenly developed a hard start problem. The engine would crank fine, but no fire. Or it would fire on the first crank. Intermittent problems are the most fun to solve, aren’t they?
Our first suspect was the battery. At nearly four years old, including lots of time sitting idle while we had the drivetrain out, our battery was beginning to show well-earned signs of age.
The excess cranking that we were doing would drain the battery after a few minutes, and voltage would drop to about 10.2 volts during the crank phase.
Our Holley Dominator needs 10 volts to start the car, but we worried that it was cutting things too close–plus our battery was clearly losing its battle with time. Perhaps we should try a different battery.
[How to make the move to an aftermarket ECU]
So we threw in another old battery that we had sitting around the shop. It tested fine but figured we’d try it before heading to battery-mart.
The Vette fired to life on the first crank. And did so the next day as well.
Then, on Day 3, same ol’ same ol’ with a crank but no start.
This battery seemed to be clearly losing its life as well as it was even older than the first one that we tried. We figured that this just confirmed our hypothesis that a weakening battery was a no-go for our setup.
So we went and got a fresh battery, dropped it in, and….
Yeah, it did the bad thing again, and we were kind of back to square one.
The ECU was checking out just fine. According to the ECU, everything looked smooth as silk. But when it came time to run, the coils weren’t getting enough juice to fire.
Then we dug deeper and checked the main relay that powers the coil banks. We found a lot of moisture-related corrosion inside. Despite being a weatherproof-style relay, it looks like the rubber weather seal had gotten rolled over during installation and was allowing moisture to build up.
So we attacked the connector with the CRC catalog, cleaning the junction with QD Electronics Cleaner and, after carefully reinstalling the rubber gasket, a liberal coating around the rim of some dielectric grease.
And, just for good measure, we put the whole thing inside a plastic bag once we were done. If it gets wet now, we’ll need a snorkel.
So, what have we learned? Well, be careful with key connections. Just because the connector is weatherproof doesn’t mean that installer error can’t override the original design parameters.
Definitely a case of; "Your killing me Smalls!"
Dielectric grease on everything!
I had an electrical battle a long time ago with just a click when turning the key. Replaced starter no joy. Replaced battery, good for a couple weeks then click. Replace battery and alternator for good measure. Good for a while then click. Dig into wiring to trace starter circuit and found a tiny 20 gauge wire jumping the ignition circuit that was like 10 or 12 gauge, installed by the genius tech at best buy that did my alarm, and it was barely even holding a connection. Luckily it didn't start a fire.
StuntmanMike said:Dielectric grease on everything!
Including directly on the connectors, this is very important for offroad vehicles that wade through muck, but also helpful on street vehicles, especially the main battery terminals. If you don't have dielectric grease handy, vaseline can make a decent substitute - just be aware it may not play nice with some rubber/plastic bits.
Guess what, things haven't changed over at GM either. I just had to replace the chassis harness and body harness in a 2020 GMC Sierra with 25k miles because there was all sorts of corrosion in the big 80 pin connector between the two harnesses. Can't count how many X500 body harness to driver's door harness connectors I've replaced over the past year for water corrosion. The new half-ton diesel trucks frequently have the charge air cooler pump connector rot out before 10k miles.
I would be interested in an article on the relative merits of "build 'em yourself" weatherproof connectors. Like Weatherpak vs Delphi for example. Why would I choose one over another? I can get a big starter kit for each one, where do I commit?
Keep in mind that no matter what you call the company: Packard Electric, PED, Delphi or Aptiv its all the same . The WeatherPack connectors are the oldest and best known sealed connector used on GM vehicles and the aftermarket. There are limitations with the WeatherPack system due to the fairly wide center line distance of the system that yields larger sized connectors, as well as the limitations due to the size of the terminals wire crimp barrels (maximum of 12ga stranding with the correct terminals) and up to 20 Amp draw limit due to the terminal engagement contact area and the temperature rise.
Later connector systems from (whichever name you prefer use; Packard Electric, PED, Delphi or Aptiv) include the Metri-Pack units, which depending on the series, offer smaller sized connectors in the 150 Series and much higher amperage limits in the 280, 480, 630 and 800 Series connectors.
Their main competitors in sealed harness connection are from; Moldex, AMP/TE, Deutsch and Yazaki to name just a few.
The sealed relay connector in question in this C5 is either a Delphi Metri-Pack or a TE unit. And yes, you can buy a replacement connector seal for these relays if they are severally damaged.
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