Chrysler Repair: Engine dies unpredictably, restarts in 10 minutes, digital voltmeter, state sensors

Question
My 1999 300M dies out intermitently. I can be in park or driving at 60 mph or stopped at a light. I sounded like water in the gas tank. I waited until I had 1/8th tank, put in an additive(B12) and it ran great. I filled up with premium for the higher octane(I have only used 89) and within 1 mile from the station it stopped. I could not restart until the engine was off for 10 minutes.Nobody can tell me what the problem is, even Chrysler. There is only 58000 miles on this car. What can I do?

Answer
Hi Bill,
When you say that Chrysler can't tell you what the problem is then may I assume that they tried to readout the engine controller for the presence of any fault codes? If not, then that is the first thing to do. The fact that it recovers in a few minutes makes me conjecture that one of the solid state sensors of the ignition system is breaking down as it gets warm, then recovers on cool down. It could be too subtle a change as to set a fault code at this point, but it should progress to setting a code. The sensors in question are the crankshaft and the camshaft sensors which can be tested with a voltmeter at the time of failure. So if you have a digital voltmeter and will tell me which engine is in the car I can point you toward the sensors in question and how to see if they are failed. Of course the first thing to do the next time it happens is to turn the key to the run position and listen for the 1 second or so hum from under the rear of the car when the fuel pump is momentarily energized. It comes on again when you start cranking but the sound of the engine usually drowns is out.  Also it is helpful to check for the presence of spark right after shut down which could 'clear' the sensors as the problem. So let me know about the engine and whether you have the voltmeter and what are the chances of being able to recruit someone to operate the ignition key while you check for spark immediately after the next event. The intermittancy means that you have to be prepared to move on it when it happens.
Roland