2002 C2 996 starts but won't run

I recently installed a new starter in my 02 C2 and was surprised when I attempted to start the engine when the repair was complete. The engine turns over and starts instantly, quickly revving as normal but suddenly shuts down after approximately 1 second. I have to sheepishly admit that I stupidly forgot to disconnect the battery before the install and got a nice spark when I touched the socket on the hot solenoid terminal. I knew there was a potential for problems but was hoping for the best. Hopefully, I have not messed up the DME! I have scanned for codes, but there are no codes in the DME. Also something curious, my scanning software does not read the VIN. Just another clue. There is a tremendous amount of knowledge out there and I hope y'all have some ideas that might help me ID the issue. Mark

Touching the hot shouldn't have done anything wrong. Unless it was touched and sparking for awhile.

Unplug the battery and leave it unplugged overnight. Plug it back in the morning. Try to fire it up. If still have a problem, check all of your fuses. Then I would start with the sensors, start by ohming out your crank position sensor. If all the sensors check out, then I would look towards the DME. No pending codes?

It was a very brief but powerful spark and it definetly got my attention. I checked all the fuses and they are all continuous. No pending codes. I will disconnect the battery tonight, reconnect in the morning and see if the condition has changed. Mark

+1 on Check all fuses Especially C 1 thru 4

don't forget to find your radio code before disconnecting the battery....

Good advice. I did locate the radio code in my owners manual. Been down that road before.... I also purchased the the Porsche module for my Autogenuity OBDII software, and plan on running a scan after work today.

My car had the same symptoms after the body shop I took it to had to jump start it. It turned out that the jump start fried the impulse sensor ($1000 repair with labor). My car also turned over and started, but died right after..... Good luck with your diagnosis and hopefully it's less serious than what was wrong with my car.

Yikes!

OK, this is getting really weird, but things are looking up, big time, if that makes any sense. Facing a potential fried DME, or perhaps a friend flywheel reference sensor, I continued the troubleshooting process. After reading a few threads, I watched the tach bounce to 300 during cranking and then briefly jump to 1000 when the engine fired, then back to zero as it shut itself down. So, I figured the speed/reference sensors were likely OK. My brother in law was visiting for the weekend and I decided to work on the 911 while he was taking an afternoon nap. Later, he wandered into the garage looking for me and I explained the whole story to him. It's important to note that my brother in law has never spent a minute working on his cars, but he is a very smart guy. He said, "Maybe the new starter is not disengaging and the engine shuts down to protect the flywheel?". As implausible as it seems, I decided to expose the starter one more time, mainly to see if I had forgotten to re-attach a sensor cable, but as long as the intake was removed, I decided to re-install the old starter, which is weak when hot, but easily starts when cold. After a few hours of now familiar wrenching, I cranked the engine and was almost shocked when it fired and continued to run! Problem solved, well, yes and no. I am back to square one, but minus a potentially difficult and expensive troubleshooting and repair, but I still have to figure out what caused the weird shutdown issue. I find it hard to believe the new starter is causing the problem, but I did not see any obvious problems with my original re-installation of the throttle body, intake and sensor wires, although I am not sure if the rubber sleeves on the throttle body to intake were seating properly, potentially creating an air leak after the throttle body. Would a major air leak cause the engine to fire, run, then suddenly shut down? OR Can the blame be placed on the starter, potentially a defective rebuild part or the wrong starter? Upon closer examination of the starter, I noticed the serial numbers on the firewall facing mounting flange are identical, reassuring, yes, but the motor on the new starter is 1 inch longer than the original. Perhaps an upgrade to the original motor? Under what circumstances could a starter cause the engine to shut down after one second? Do I go with the leak theory and swap the new starter back in, or do I assume the starter is defective and arrange for an exchange? Your thoughts and opinions are greatly appreciated. Mark

We almost need a full time porsche tech to monitor the website. Strange stuff. Possibly a connection wasn't right or didn't have a good connection. I wonder if any of the connectors allow the plug to be reversed.

Seems like some of the guys in this forum know more than the average tech... The 3.6 engine is designed in a way that would make it difficult to reverse a connector, but I could see losing track of a connector, leaving it unplugged. I checked all the connectors to ensure they were seated properly. That doesn't rule out the possibilty of a loose wire in one of the connectors. Also, the starter wiring is about as simple as it gets. One wire, split between the battery and generator, connects to the 12v supply terminal on the solenoid, and the solenoid control cable connects to the other terminal. There is no way to mess it up. I am tempted to swap the new starter in with an eye toward ensuring a leakless install of the throttle intake tubes. If sucessful, that would elimimate the starter and implicate a botched intake install on my first attempt, but I would be done. If I experience the same failure, then the problem is certainly the new starter, and I arrange for yet another starter but probably from a different vendor. I would like to hear a few more guys weigh in before I tear into another starter swap. Mark

A big air leak will screw you up. I think you have to reinstall the new starter.Verifying no leaks. The worrysome part is it's one inch longer than the original motor so is it retracting enough after it starts the car to get the gears out of the way of the flywheel?

Since the new starter pinion gear is in the exact same static position as the old starter, it should not interfere with the flywheel once retracted, but is it retracting due to the potentially longer armature throw? Just a wild theory? Probably. I can end the speculation in about two hours by just swapping in the new starter.

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AFAIK, there is no interlock that kills the engine should the starter pinion fail to retract. The starter gear must engage the flywheel before the starter motor is energized. The starter solenoid also must be able to hold this engagement Upon engine start if you delay in allowing the key to return to the engine run position, the pinion gear has an clutch so the flywheel can't overspeed the starter motor. If this were sticking you'd know it. My WAG is there was a wiring/connection issue. However, I'm always a bit leery when it comes to installing parts -- in this case a starter motor -- that is not an exact at least physical twin of the old part. I would be concerned about a starter pinion gear not fully engaging the flywheel, which would at first be just accelerated wear/tear on the partially engaged gears with later on starter gear pop out as the gear teeth became rounded off. Or the starter pinion gear clutch gets spun more as the starter gear remains engaged longer after the start operation. At first maybe no problems, but over time the pinion gear's clutch suffers from this. Sincerely, Macster.

My vote goes to air leaks. If the MAF isn't getting airflow from the engine sucking air through it, it won't provide the necessary fuel to keep the car running after initial startup.

I had similar issue with a C280 mercedes - shop had done some work on the car, but then it would not run after start. He asked me to bring over spare key. Same problem. WHen I opened the hood, I noticed the rubber boot for air intake was not seated properly on the intake - I re-seated it - and then the car ran with no problems. The mechanic was highly embaressed. So if by putting the old starter back you re-attached some of the air intake hoses - that could have been your problem ...

If you had a huge air leak the car would probably run and it would sound like absolute crap. If you want to see what that sounds like you can pull back one of the boots and create a big air leak. It runs, but just horribly so. I would take your new starter to an auto parts store and have it bench tested for free. If it checks out OK, I would reinstall it, being extremely careful to get all of the wiring back together correctly.