sbenner

Hello, I have a 1991 Corvette, base model with L98 engine and ZF6 transmission. I had a major problem tonight and was hoping you guys could help me with diagnosis. Please forgive the long post, im trying to be as detailed as possible.

I was driving home, enjoying the air conditioner, and all of a sudden the car completely shut off for about half a second. Total power failure at 50mph. The gauges went black and everything was shut down for a moment as the car jerked hard when the instantly dead engine slowed the vehicle. Then just as suddenly there was power and the car is running again like nothing happened. But the radio clock had reset itself so I know there was zero power for a moment.

So I pull of the road, look under the hood to see if the battery, alternator or spark plug wires were still there. They were all still connected nice and tight. I start it up and drive slowly a short distance to a nearby business complex to do some test driving to see if this is going to happen again.

I start off by parking it and letting it idle; as it idled I noticed the gauge lights were lightly flickering. I tryed to draw as much current as possible, turn on lights, ac, hold breaks, and roll windows all at once. The car kept running, and the gauge lights kept lightly flickering. So the extra power drain didn't seem to have much effect. I let the car idle normally for another minute or so... and it just completely shuts down again.

Now I turn the key and try to restart it, and get nothing, not even a click. But when I take the key out of the start position I hear a very quiet alarm sound. I mean very quiet, but it did sound like a light beep then light warning sound. It only made the sound after turning the key to start then releasing. I tried a couple more time and got the same result. This "alarm" sound was happening while there was no power to anything else, I couldn’t even flick on the interior lights.

So I instantly figure... this must be some kind of crazy (and extremely dangerous) example of a vats failure. Let the car sit for a few minutes, turn the key, and it starts right up. But the gauges are still flickering and the idle doesn't sound as smooth as normal. So I turn it off and let the engine cool for about 15 minutes. Start it back up and the gauges are still flickering. I drive around the complex some more, trying some brief aggressive launches and shaking the steering wheel (testing for some kind of loose connection), no affect, the gauges continue to flicker lightly.

After driving around the complex for another 10-15 mins I decide that I simply cant trust the car to take the freeway home. So I pull into one of the business parking lots and call AAA. While waiting for the flatbed I start it up again, now it goes crazy. The car kept idling as all the power in the car start cycling on and off. All power in the car was turning completely off and flashing back on very fast (about 4-6 times a second). I quickly turned it off. When the truck got there I tried once more and it stayed on for a few seconds then slowly shut down.

And here I am, the car is unloaded in the driveway. So what do you guys think? Something is cutting out the main circuit in the car (battery and alternator). Is the vats system capable of shutting off ALL power? Or is this a symptom of something else? Any ideas would be helpful.

Thanks!

Demonic85

Yes, the VATS system can cut all power, but I dont know if it can do that while driving. Hopefully someone else will pipe in with some better info.

CJB

VATS. This same thing happened with a friends 87 model in down town Tokyo 5 or 6 years ago. Code it. Search the information out in Tech Tips, or archived threads.

Midnite 88

Clean your battery terminals. Check the voltage.

I think VATS is a long shot.

morgan_kane

I can only speak as owner of older model (-87), but there vats system is designed so, that it cannot shut down all power. Lights (for example gauge backlights), radio, a/c etc. are not behind vats system. Only engine electric can be disabled by vats. I don't believe it is vats. Total blackout can only be caused by battery or it's connections. And if your lights were flickering, i assume that battery is not connected well, so it can't neutralize alternators voltage ripple. And, because your car can start, i believe you should start checking from battery connections; there is big cable going to starter, and i think it is good, but the other cable transports current to all other systems, maybe there is loose connection in there or in the fuse box. I believe it is easy to find, if you start car and wave the cables near battery and fuse box. Maybe you seem some sparking or car stops.

It is loose connection somewhere in main connections, i am 90% sure.
Of course your battery may have internal shortcut also.

jfb

VATS only prevents the starter from cranking and the injectors from being pulsed by the ECM if the pellet is not the correct resistance. VATS isn't the cause of your problem. The most likely cause is an intermittent connection from the battery to the ignition switch because almost all power to the engine and cockpit goes through the ignition switch. Even if the battery became disconnected from the battery cables, with the engine running, the alternator will run the car, but if the ignition sw becomes disconnected from the battery/alternator, then the field current to the alternator shuts off and the engine will quit and almost no electrical stuff will work. I believe the 91 has a block of fuses near the battery and one goes to the ignition switch (I may be wrong about this). Check the connection from the battery positive terminal to the ignition switch.

thebeerman

I would check all of the engine and body grounds. There are more common electrical problems traced to bad grounds than any other single problem in fibreglass bodied cars. Make sure all connectors are tight, aren't corroded (star washers under every bolt help), and if any of the cables look worn or frayed, replace them. Checking your grounds won't cost you anything, and even replacing cables is cheap. If that doesn't show the problem, follow the path from the battery to the ignition switch and fuse panel. If there is a major fuseable link of relay that is defective, it could shut down the entire system. At least these steps you can do and won't cost you anything.

SJW

This is excellent advice.

I would add to also check the ignition switch itself. Jostling it a bit while running would be a good place to start.

Good luck with it. Please post a follow-up when you resolve the problem.

Be well,

SJW

sbenner

Got the problem solved. Turns out it was the power distribution block behind the battery.

In my car the positive lead comes off the battery and connects to a distribution block behind the battery, where several wires and fusible links send the power through the car. This block and all of the connections on it had become horribly corroded and interrupted the circuit.

Sanded down the connections, cleaned the block and sealed it all up. Now it runs great again. I highly recommend cleaning this item in your car if you notice it becoming corroded. I'm also going to upgrade to an optima battery, trying to removing some of the acid that caused this to happen.

Thanks for the replies everyone!

kenv

Thanks for posting your fix for the problem. A lot of folks have posted their problems, asked for help, & then never bothered to tell the forum what fixed the problem.