Wont Start, now Battery Problems

[silver356]

I'm looking for some input from you guys, as I'm having some confusing issues with a 72 with Webers. Ive had the car for a while, but its been sitting, and I'm trying to get it to driver status. The car has had some recent work, Webers rebuilt, rebuilt alternator, tuneup, new upgraded coil, all about 8 months ago, but since then, car has sat. Ive been working to get it on the road, so I was dealing with some parking light and headlight issues, finally got all of those solved. Id start it every once in a while, idled fine, sometimes need a trickle charger overnight to get the battery up, but always started. Decided to give it a drive, and about 5 minutes in, started sputtering, died once, restarted, limped over to my mechanic, a few blocks away. He sorted some issues, put on a new cap and rotor, seemed to be getting both spark and gas, but would not start. At All! It was the end of the day, and he was slammed with work, so towed it back to my place.

Couple of days later, decided to check the CDI, and try some spares I have, but battery was completely dead- I think the flashers might have been left on when we were towing it back. Tried to hook up the charger, but it kept failing, like it was shorting or there was some load on the battery. I unhooked the battery, pulled it out of the car, and then the charger worked fine. Charged it up, but when I went to hook it up, got a huge spark when I touched the negative to the terminal ( hooked up positive first.) Volt meter in series with the ground wire and terminal showed 12v draw. Everything is in the car is off. I even took out almost all of the fuses, still a large draw.

What could the draw be? Bad ignition switch? Is this an alternator issue, is that why the car wouldn't start? Or did it get destroyed when the battery went dead?

Any thoughts on my best course of action?

[Porboynz]

A few things to deal with here. First, any battery charging should always be done with the battery earth disconnected, the so called battery tenders that you can connect up with the battery still connected in the car are not up to recharging a battery that is seriously discharged. So get that battery charged with a decent multi stage charger and make sure its good. (your local battery supplier can load test it for you and advise condition) Batteries that are allowed to go into deep discharge have a short lifespan.
Next it sounds like you have excessive parasitic/vampire current with everything switched off. You need an ammeter to measure this current, not the voltmeter. A simple test is to connect up a headlight bulb in series with the battery ground, the brighter it glows the larger the current. Then its a simple matter of isolating the current source by pulling fuses and disconnecting possible loads. Well its simple in theory but can often be frustrating, especially if there are 2 faults. You may have to disconnect your starter and alternator once all the easily isolated possible loads are removed. Never assume anything, just because a switch is off does not mean it is off, same with the ignition switch. I am guessing a bad diode in the alternator.

[Joe Bob]

Fully flat batteries need a shock to bring them back. An old school ANALOG charger is needed. One hour at full 10+ amps (if it has a "start" option use that), then 2 amps, 10+, repeat until the meter shows zero. This can can some time....as much as 8 hours.

NOTE: while digital chargers have their place, their design does not allow fully flat battery charges. "Dumb" analog chargers just do their jobs and don't "read" batteries and decide if it wants to work. I have both, my 30 year old Sears model gets the most work.

Charge it with battery out of the vehicle, vent caps off if you have them, check electrolyte levels in the cells, use distilled water if they are low. WHEN it is fully charged, take it in to a shop for a load test. OR DIY test....consisting of trying to start the engine with ALL the lights on. If they dim while cranking it is likely that the battery has a bad cell or internal short.

If the battery doesn't take a charge, won't turn over the starter, has other issues. Consider the replacement with a marine style boat battery. I use a Yellow Top Optima. They are designed to go fully flat/discharge. They are used for electric trolling motors and 12v back up when boats are idle.

An old 911 will likely sit a bit and batteries will discharge over time. As such I back it up with a Battery Plus, battery tender. The kit has a permanently attached pigtail with a protective rubber end cap. Mine hangs out the frunk for ease of access (not having to open the lid).

Anytime I don't plan on using my 911 for more than a day, it gets hooked up. My last Optima lasted 15 years. The current one is going on 5.

Or if you are impatient, just buy a new battery....
Be sure the replacement has a full charge. Nothing kills an alternator faster than a low battery. Alternators are maintainers, not chargers. High loads on the alt while trying to bring the battery back up to 14v while running other devices in the car are not good.

Hope that helps, good luck. Sorry for the long-winded reply.

[silver356]

Thanks very much for your help! I guess I miss titled the post, as its really not the battery that's the issue. I am using an old analog battery charger, its just a small one, so I call it a trickle unit. I had no problem getting the battery charged to 12.8 , but what I'm not understanding is how a dead battery can cause the alternator to go bad, especially when the car has not been run since the battery died, and the alternator was just rebuilt. Is it just the fact that the battery died, and when I turned the key, and got nothing, it screwed up the alternator?

I took out about half the fuses, with no change, and I'll take out the other half, and try the test that Porboynz suggested, using a multimeter.

Just to clarify, though, when hooking up the battery, in an early car without computers or such, there should be no spark when you hook up the neg terminal, right, because there should be no draw in an early car ( I have no clock). I guess what I'm trying to figure out, is what changed while we were trying to start the car, that has now created a short or draw that's not through the fuses...

[DaveMcKenz]

I've had bad alternator diode as was suggested above. Also you had it rebuilt recently.
Good luck,
Dave

[Porboynz]

My 911 has an older mechanical clock and it still draws a spark when I reconnect the battery terminal. I can go about 3 weeks without starting and still have plenty to crank the engine, the battery is about 5 years old now. I am too lazy to hook up a charger unless the car is not going to be driven for more than 3 weeks. A flat battery is hard on an alternator but not usually fatal. Disconnecting the battery when the engine is running is often fatal for the alternator which suddenly has no load. Or was your alternator new and then you had problems, not sure from your post.

[T77911S]

i missed in the first post were you said the alt is bad. why do you think it is bad

you don't measure voltage between the battery and the cable. you measure current (amps).
it takes only a very small amount of current for you to measure voltage. the clock alone will allow you to measure 12v between battery and cable.

are you sure you connected the charger correctly when it "failed' with the batt in the car. it si very easy to connect it wrong. I have seen red neg cables and black pos cables. always verify either on the battery on which cable goes to chassis.

as far as the big spark when connecting the battery. on a new car that may not be a big deal as there are more electronics but with your 72, you may have had something on when you connected or you have a big draw.

as far as not starting, when I had carbs I would look down in the carb verify the accelerator pump was spraying fuel into the carb when I operated the throttle. that verified that at least fuel was getting in the bowl and the jet was clear.
just because fuel gets TO the carb does not mean it is not getting in it.

it does seem odd that it would not at least fire. that would mean a problem with both sides.
you may want to keep in the back of your mind junk in the tank and/or fuel filter. (from sitting).

alternator needs to either be removed and tested or tested once you get it running.

check voltage of battery WHILE cranking. should be greater than 10v. a fully charged 12.6v battery can still be bad.

[silver356]

Just a quick update-not much time this weekend( not located where the car is, about 40 minutes away). Took out all of the fuses, and still drawing 7.1 volts. I'll go back and check amps this week. Two questions come to my untechnical mind; What unfused draw would there be? And, am I overthinking this- does it matter there is still a draw, should I just hook up the battery, spark and all, and move onto trying to get the car started?

To answer an earlier question, the charger was definitely hooked up correctly in the car, and it was definitely hitting a short somewhere. And to another question, I'm not saying the alternator is bad, I'm just asking if that could be the unfused draw, or if having a dead battery would fry a part of the alternator that would create an unfused short in the system...

[T77911S]

again, voltage is NOT a draw. well technically it is but for this purpose it is not so you don't measure voltage.

here is a prime example proving the opposite point.
I have seen many times guys trying to fix a no brake light problem.
they measure voltage at the light and get 12v but the light does not light.
the problem is the current is so low at the socket it will not light the light but there is enough current or potential between pos and neg to measure voltage.

you may have enough current to measure voltage but not enough to drain it over a normal amount of inactive time.

[Porboynz]

Originally Posted by T77911S

again, voltage is NOT a draw. well technically it is but for this purpose it is not so you don't measure voltage.

here is a prime example proving the opposite point.
I have seen many times guys trying to fix a no brake light problem.
they measure voltage at the light and get 12v but the light does not light.
the problem is the current is so low at the socket it will not light the light but there is enough current or potential between pos and neg to measure voltage.

you may have enough current to measure voltage but not enough to drain it over a normal amount of inactive time.

The man speaks the truth, measure the current not the voltage. The alternator will have a voltage differential across the diode pack but I have never measured it at the battery as you are doing so cannot comment on what is normal. Wiring in a light bulb is a quick indication, if there is not enough current to light an indicator bulb then the current is fairly low. If it lights up bright with all the fuses out and switches off you have a problem to track down. At least you will not destroyed your ammeter using a light bulb.

[T77911S]

i have always used a test light. even for current draw. but it is a bit judgmental on how bright is ok. if it is as bright as going across the battery you definitely have a problem, plus a light is easier to see from a distance.