Stranded! DME Ignition Guru Help needed

[jbrinkley]

I'm wondering now that if I got stranded could you still push start your car?
I was thinking about getting a spare for the break down kit.

[Thrasher]

Not a Carrera - no way. That sensor that went out tells the computer (DME) where TDC for piston #1 is; it then uses that to calculate where the flywheel is relative to that position. Apparently it only reads this value at starting and ignores it, using the 2nd sensor for flywheel/engine speed. The sensors are identical, but the speed sensor counts flywheel teeth and the reference sensor just blips when the metallic slug passes by it, once/revolution.

Since my sensor was dead, the signal was never sent to the DME and as far as it was concerned, my flywheel was not turning, so it never "released" the signal to spark the coil.

Dead in the water (parking lot, actually).

[jbrinkley]

I'm with ya now, thanks

[rick-l]

Originally posted by jbrinkley

I was thinking about getting a spare for the break down kit.

These sensors consist of a permanent magnet and a coil of wire. No moving parts, no electrical stress, should be pretty reliable.

I wonder what other parts have the same failure rate and what you would have to start carrying around to have spare parts available that have that failure rate or greater?

[jbrinkley]

that and CHT, DME and a couple relays, fuses stuff like that.

I'm talking about maybe getting stranded in the middle of texas where I might really stuck

[Thrasher]

I think the operative word is "should". Yes, they are said to be among the most reliable sensors on the 3.2's.

Ok, I'll qualify that. If you can't say for certain that your two flywheel sensors (3.2 L) have been replaced in hmm.... 40k miles or 5 years, you may want to keep a spare on hand.

Here's a thread that talks about the anti-strand kit. How To Avoid Strandings?

Realistically, I didn't have nearly the tools it would've taken to fix on-site anyway. But, my 911 has been sitting where it was towed (in my garage) for over a week while I diagnose, wait for parts, etc.

But, it's not my daily, and I have taken the "while I'm in there" approach.

And, NO - this sensor gave absolutely no warning before complete failure. The threads I saw show the wire insulation failing in most cases. My insulation was pristine, but you can easily check this by looking in your right-rear wheelwell with a light. The sensor wires emerge from the rear of the wheelwell, above the heater ducting and loop back towards the flywheel.

Speculation is that the proximity to the exhaust and elements gets to the insulation and/or wiring.