I seem to have an electrical drain somewhere in my car. Anyway, my battery is now dead, and I'm trying to jump start it. The jumper cables are connected correctly, but when I try and start the car it just coughs a bit, and doesn't start. What's the problem/how do I fix it?

 

Hi Eion,
what car are you using to jump start the Porsche? Use a car which has a battery with an +/- equal size as the one in the Porsche. Probably its battery is also not in good health anymore. Start that car and push the throttle while someone else is trying to start the Porsche.
Greetz.

 

I'm using a Jeep to start the Porsche - it's battery should be OK, but it's only a 540A, so that might be the problem. I would try starting the Jeep and starting the Porsche, but I'm all on my own in the middle of nowhere, with only the Porsche, the Jeep, and the Internet :¬( - I think I'm going to have to go into town and get a mains-powered battery booster.

 

Hi Eion,

Jumpin' cars is my expertise...well, ya gotta be good at doin' something, right?

1) A real dead battery acts as a major drain on the vehicle you're using to jump from. The power from that vehicle is consumed in the dead battery and your starter motor is not getting max. amps to turn. Once you drain an auto battery to that extent, unless it's new, it usually damages the capacity to charge and hold a charge. You can take the battery and put it on the charger, and probably use it, but it won't be reliable. The breakdown of the battery causes irrepairable internal resistance which acts as a load. In a pinch you can disconnect the dead battery, hook your jumper cables to the leads and restart the car, then carefully reconnect the lead, but only if you are stuck in Baja driving a Landcruiser and running out of tequilla, but that's another story.
2) Your jumper cables aren't bitting in the terminals or you have corrosion on your terminals your jumping to, or the vehicle that your jumping from is not running it's engine. You need the best conditions to jump a car, because of the limitations of the jumper cables.
3) Time for a new battery...been there, done that...BUT find the drain and keep the battery disconnected when not in use until then. Usually some vanity light in the cab or trunk, or alarm system. There's been plenty of posts regarding this problem, you gotta do a search.
<img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" />

 

[quote]Originally posted by mojorizing:
<strong>..... but only if you are stuck in Baja driving a Landcruiser and running out of tequilla, but that's another story. </strong><hr></blockquote>

Sounds like the kind of story we need to hear more of .....

<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

Thanks for all the help, guys!
Yep, the Jeep wasn't running when I was trying to start from it - it said in the instructions (and my owners manual) that the booster vehicle shouldn't be. I've never jump-started a vehicle before (this is my first car, the Jeep is a loaner from my parents), so I was following all the instructions *very* carefully. I also *really* didn't want to damage the Jeep, partly because it's not mine, partly because the alternative is a long walk...

The battery looks pretty new, but I've only had the car for about 10 days. I've got it on a charger at the moment - I'll see if it's worked in a few hours. I *really* hope so, otherwise I'll have to take advantage of my emergency rescue callout.

I *suspect* that the battery drain was my drivers side door light. I've switched both interior lights off in the meantime.

Thanks again!

 

The charger worked it's magic, after 5 hours or so. Took it for a drive after letting it idle for 10 minutes - seems as good as new now :¬)

Thanks again for all the help :¬)

 

This isn't a criticism - sometimes you can't do the right thing whatever you do - but 964 engines don't like to idle too long from cold.
Apparently, the camshafts don't get a decent oil supply until a few revs are built up.

 

Way ahead of you there :¬)
I read what was in the manual about letting it idle for about 10 minutes (the idle was *really* rough when I first started it up), but I'd heard somewhere (probably here) about the idling from cold - so as soon as I was sure it was started I slowly took the engine to about 4000 revs for a short period of time... of course, I'm sure that's doing something wrong too... I really don't know my way around this car very well yet.

Anyway, I had a quick look for a power drain and couldn't find one, so I guess all this experience/advice will come in handy next time the power drain fairies pay a visit...

 

[quote]
Anyway, I had a quick look for a power drain and couldn't find one, so I guess all this experience/advice will come in handy next time the power drain fairies pay a visit...<hr></blockquote>

you could head off those fairies with a little pixie dust.

pull off the positive battery lead and put a voltmeter between the post and the lead. it should read about 50 mV (.05 volts) or less. remove your fuses one at a time until the voltage on the meter drops. that's the circuit with the voltage draw...