Hooking up battery charger reverse
 

Help. My battery was dead on my 83 930 and in hast, I hook up my battery charger backwards and tried to start the car(the starter cranked). Now the car won't start and when the engine cranks, it doesn't sound so good. There is no spark or sounds from the fuel pumps.

Most battery chargers have a fail safe that will not allow them to operate if hooked up incorrectly. Sounds like your battery is still dead. Just hook it up correctly and see if the battery will charge.

Yow! This is an issue for the EE's on the board; can the starter run backwards? If it can you may have cranked the engine backwards and the cam chains don't like this much. Also the oil pump won't push oil the right way running backwards so there probably wasn't oil pressure. You also may have burned out the alternator diodes, ruined the battery and put other polarity sensitive electrical components at risk. Not good at all. Get it hauled to a mechanic who knows what he's doing. Hoping for the best for you. Jim :eek:

Write out a hundred times;

"I will never try and jump-start my Porsche again"

If you have a dead battery, the correct procedure is to disconnect the battery, charge it to fully-charged, check it and refit to the car. NEVER jump a dead battery and try and start the car, the power requirement on the alternator to charge at full rate will overheat the alternator.
Alternators are designed to maintain the battery, not charge it from dead......

My guestimate is that you fried the red fuel pump relay and CDI-unit, alarm system, and perhaps the blinker relay, and delay wiper unit ... if the battery charger did, indeed, supply significant current in reverse polarity to the electrical system! Check for blown fuses ... they may have prevented a fire, but couldn't act fast enough to protect many semiconductors from reverse polarity, as it only takes a few milliseconds to overheat and blow out the semiconductors!

Did a similar thing on a 77 Honda CVCC a few years ago. Battery was dead and got a jump from a friend. What I didn't know was my friend put the red cables on the neg side and the black on the pos (lesson learned...check the polarity ON the battery). Yes, I hooked it up wrong...spark and an engine not running. However (and the whole point to the story) was I merely blew out the engine's fusable link (only a couple bucks to replace...which I bypassed temporarily until I got the replacement, but not recommended) with no damage to the car's electrical system. Question: is the porsche similarly protected?