electrical problems
Thread Starter
Heel & Toe
Joined: May 2003
Posts: 15
Likes: 0
From: orland park il
electrical problems
i have an 87 vette brand new battery brand new alternator. after the car warms up and idles at normal my volts drop to 11.xx when i start to drive the car it goes back to normal 13.xx when i come from a compleat stop and then try to get going again the car starts to hesitate and back fire until it gets going. any ideas as to what my be wrong with it???????
Melting Slicks
Joined: May 2004
Posts: 2,524
Likes: 10
From: Lufkin Texas
St. Jude Donor '05-'06
You may have a dieing alternator that doesn't put out enough at low rpm's but does better when turning faster. Brand new doesn't always mean working proper. Have it and your battery load tested at idle. Most auto parts stores like auto zone will do this free. You may also have a weak wire between the alternator and battery. Check output at alternator post versus output at battery at idle. Should both be in the 14's while at idle. Then 12-13 with car off. If there's a big difference you need to check wire and it's connections from alternator to battery.
Drifting
Joined: Nov 2002
Posts: 1,593
Likes: 0
From: Mobile AL
St. Jude Donor '05
Sounds to me like you have a problem with idle speed, not an electrical problem. If it's charging at 13.x, that is a tad low, but acceptable to keep your battery charged. The key here is that it hesitates and backfires when you accelerate - that tells me that you've probably got a problem in the fuel system.
Safety Car
Joined: Jul 2001
Posts: 3,833
Likes: 0
From: Orange County California
Originally Posted by 87vettte
i have an 87 vette brand new battery brand new alternator. after the car warms up and idles at normal my volts drop to 11.xx when i start to drive the car it goes back to normal 13.xx when i come from a compleat stop and then try to get going again the car starts to hesitate and back fire until it gets going. any ideas as to what my be wrong with it???????
Le Mans Master
Joined: Dec 2002
Posts: 6,715
Likes: 2
From: Santa Teresa New Mexico
Originally Posted by McShagger
Dude, I dont want to speculate, but it does sound good... give us some more background info on your car...
It sounds like two different problems.The miss and lack of power sounds like a tune up is in order.
New cap and rotor with new pugs and fuel filter couldn't hurt.
It might also be an under-charged battery.
Charging shouold be at least 12.5 at idle. 11xx wouldn't keep up with the battery altenators charge at idle, generators don't.
Thats why the switch to altenators in the 60's.
A new battery should be charged before the install they lose 40% shelf life while sitting.
Check your batterys voltage while the car is sitting. Should be at least 12.50.
Always charge a new battery before putting it into service.
Go back to 0 and charge that battery and then go from there.
You can get a Chinese battery charger from China Inc, Wal-Mart-Target-Sears-Kmart.
Radio Shack has a good Chinese volt meter. Get a digital they're easier to read. You're going to have to get handy with one sooner or later.
But you probably already have one.
Good luck.
Melting Slicks
Joined: May 2004
Posts: 2,524
Likes: 10
From: Lufkin Texas
St. Jude Donor '05-'06
The reason I say check the wire from alternator to battery (or distribution block) is because I had simular symptoms after bringing my sleeping beauty out of the hibernation the previous owner put it in. The alt. was putting out like 14.7 while the battery/distribution block was only seeing like 11.5 at idle. The guage in dash was showing like 13. After a few long redlight stops with all 5 power sucking brake lights on, the car would sputter/buck/die, but when I got it restarted and kept the rpm's up I was able to make it home. I guess the ignition/ECM and other systems must have 12 volts to properly function.
After some close examination I had some un-visible corosion under connections at alternator and at battery distribution block down low behind battery.
It may not be your trouble but it couldn't hurt to check these and take them loose and clean them up inside.
After some close examination I had some un-visible corosion under connections at alternator and at battery distribution block down low behind battery.
It may not be your trouble but it couldn't hurt to check these and take them loose and clean them up inside.
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Thread Starter
Heel & Toe
Joined: May 2003
Posts: 15
Likes: 0
From: orland park il
just got a new fuel filter that didnt help this is also the second alternator that i put on same problem. the out put at the alternator is the same at the battery 13.xx if i am reving it or at idel around 11.xx
Melting Slicks
Joined: May 2004
Posts: 2,524
Likes: 10
From: Lufkin Texas
St. Jude Donor '05-'06
Unless your idle is way low or your belt is slipping then I'd say your 2nd alternator is also bad. Check your idle and belt tension. If they're ok then maybe the third alternator will be the charm. You should have 13 plus volts to 14.8 at alternator at idle. and maybe a hair less at battery.
Safety Car
Joined: Jul 2001
Posts: 3,833
Likes: 0
From: Orange County California
It does sound like youve been doing the right things to correct the problem. However, since its not doing anything to fix it, its probably something else... and thats why I didnt want to speculate. It could be something as simple as spark plug wires...
You need to tell us more information... How many miles on the car? Last spark plug change? Kind of spark plugs? Spark plug wires? Compression check? Its always really easy to check your fuel injectors. Give em a quick check.
You need to tell us more information... How many miles on the car? Last spark plug change? Kind of spark plugs? Spark plug wires? Compression check? Its always really easy to check your fuel injectors. Give em a quick check.
Melting Slicks
Joined: May 2004
Posts: 2,524
Likes: 10
From: Lufkin Texas
St. Jude Donor '05-'06
If you think you have a fuel delivery or spark problem and you haven't corrected the first issue of low voltage then you do. Because neither fuel pump or ignition or any systems work well at 11 volts. First tackle the low voltage thing and other suspect problems might disappear. Spark and fuel delivery dont cause an alternator to put out only 11 volts at idle but on the other hand 11 volts will cause a problem with spark and or fuel delivery, among other things.
Check and make sure your base idle is up to par after warm up and/or do whatever it takes to get your charging system at or above 12 volts at idle.
Check and make sure your base idle is up to par after warm up and/or do whatever it takes to get your charging system at or above 12 volts at idle.