vracer99

I have a 1985 Vette with only 318 miles that has been stored for 30 years. I've just been thru the process of getting it running after sitting all those years. Put MMO in the cylinders, let sit overnight and then hand rotated the engine 6 full revs. Then put new battery in & cranked engine with the plugs still out to build oil pressure to the upper valve train & blow out the MMO. Drained the old gas in tank & put in 2 gallons fresh premium. I didn't do anything else to the fuel system, gas tank, fuel pump, or lines. When hooked everything back up and tried to start I now have a multitude of problems. The big issue I need to fix 1st though before I can address anything else is this. Was very hard to get to start & run. When it finally did it runs very rough and will only keep running if I hold at high RPM around 3000. When I did this the volt gage showed a red light and 18.1 volts! It overcharged the battery so bad it blew a lot of battery acid out the vent tubes. Can anyone help with what may be causing this very bad overcharging?

Square

Overcharging is caused by a bad voltage regulator in the alternator. You will need a new alternator or a rebuild of the one you have.

Having to hold a high rpm to keep the engine running is often a sign of a significant vacuum leak. A smoke test will show if that is the cause.

billschroeder5842

Your voltage regulator is.. not...regulating.

Congrats on a low mileage beast, but as you are discovering that "waking her up" is no an easy task. My guess is that you will have a lot of cleaning and un sticking to do.

vracer99

OK, but remember this is basically a brand new 30 year old Vette, (only 318 miles). Would the voltage regulator in the as new alternator go bad from just sitting in the garage all those years without being run? Also what method do you use to do the smoke test?

xrav22

Answer is yes and no . Did it fail, probably not but it did collect moisture and corrosion is happening inside, so you have to go by the signs it is
giving. Clean connectors on alt , battery. Good luck!

vracer99

Thanks billschroeder5842. I was replying to Square when your response came thru. I figured it probably was the voltage regulator but couldn't figure why it would go bad from just sitting & that's why I'm stumped. One of the other problems I'm having is besides it running very ragged & missing, is the left cylinder bank seems to be getting much hotter than the right side after just a couple minutes of running. This would kind of indicate most of the misfiring is on the right side. What would cause this?

vracer99

Thanks xrav22. I'll try cleaning all the connections and keep my fingers crossed.


One more question to anyone. Could this extreme overcharging for just a few minutes have caused any damage to the ECM?

xrav22

This is what can happen. My ecm worked fine but I didnt even know I had an alarm system. I thought I would clean the ecm connectors with spray, and I found a module next to it. I cleaned all connectors and I found I had a working alarm system. My point is you will need to clean every connector on the car . That would be my guide.

billschroeder5842

Yes, but I'd not jump there yet.

My suggestion is that you give your car a chance to "wake up" slowly. Although "newish" after 30 years, it is certainly not a new car. There is more rust, corrosion and deterioration than you can imagine.

You high idle is probably the result of a vacuum leak. Any thing rubber is suspect and prone to cracking. Being pressurized (and expanding) for the first time in 30 years, you will no doubt have air and fluid leaks.

Your running rough is probably your injectors being dirty (gasoline that has turned into a varnish type substance) that will either work themselves out or need to be replaced. Your fuel rails are most likely gummed up.

Your engine sensors connections probably need freshening. Start with your coolant sensor, then IAC and the O2.

Cliff Harris

The ECM has over voltage protection built in. It will shut off the engine if the voltage gets too high.

70ZZ3 96LT4

Voltage regulators are not difficult to replace in a 1985 alternator.

vracer99

So I can replace just the voltage regulator and not have to buy a whole new alternator? Some say the regulator can be replaced and others say it cannot unless the alternator is taken to a rebuilder. Is this something I can do? Are there instructions online anywhere?

vracer99

Thanks to "ihatebarkingdogs" for both your responses. 1st, I didn't think the ECM would shut down the engine in an over voltage condition. I had read where this would damage the ECM if operated for a prolonged period. Hopefully mine is not harmed as it only ran a few minutes before I noticed the red over-voltage indicator & 18+ volts on the gauge.
2nd, thanks for the info on changing the regulator and also the things to test before changing it out. I shouldn't have a voltage drop on this car, but I'll check it.

Cliff Harris

That's the way that I remember it, but it's been a couple of years since I looked at the code. Something to do with overheating the injectors if the voltage is too high.

I looked briefly at the code just now and only found the error code 53 if the voltage is over 17.1 volts.

aklim

Why would you want to do that? You can replace the regulator but it is kinda old so I would take it to a rebuilder and have them go through it. Make sure other things are in spec and not on the way out. You can change the regulator yourself if you have a couple tools but you can't test it. Before you ask, I had Autozone or a store like that test my starter. They said it was OK. Rebuilder found oil leaked into it and crudded up things. I had to teach them how to do the ignition module test. Sorry, not much faith in these stores.

confab

Given all the computerized gizmotry in the C4 and if it is actually boiling electrolyte out of the battery? I wouldn't play games with this AT ALL. Just change it, imo.

I bought a really, really nice van once and it ran FINE. Everything was perfect but the trans was out, so I got a steal on it. It sat for a couple months till my parents said they wanted it, so I went to put a trans in it and the engine is locked up! I can't believe it. I parked it there myself!! It was fine!!! FTW?

Well, the alternator managed to corrode a little bit and stuck the armature. I tried to break it loose and it actually cracked the case. It stuck that bad.

There's no telling what is going on inside a 30 year old alternator. I'd just replace it and potentially save yourself a host of problems.

But, that's JIMO.

Good Luck!!

billschroeder5842

I like that. I'm going to steal it, use it and call it my own.

Thanks!

billschroeder5842

That what I'd do. You have a unicorn.

confab

There's something to be said for that too.

If it is important to you, OP, I just googled about a billion GM alternator rebuild videos on youtube. (Only a slight exaggeration, I assure you.)

It's pretty old, so you can at least give it a good once over when you're in there and hopefully spot any other lurking crap.

Good Luck!

confab