No start post oil change, WTH did I do ?

[Greg D.]

I changed the oil on my 72, only minor oil spill this time ;-) After refilling it occurred to me to crank the engine w/ the coil to distributor lead disconnected to prevent start and distribute some oil in the case... Not sure why. I usually don't bother...

After five seconds or so, I go reconnect the lead, and.... still no start... It cranks strongly, I can hear the pump whine, all normal except no firing up... Was that a no-no on this car ? Could I have possibly blown up a relay, the permatune itself, something, by cranking without a distributor lead connected ? Seems like too much of a coincidence, it's gotta be my fault.

I'm out of relays, I did swap the lead to no avail... Now it's stuck in my garage at the bottom of a steep driveway so I'd like opinions before I shotgun parts orders (coil, relay, $$$ CDi). I have voltage at the red pin of the CDI, I'm guessing I blew the CDI by unplugging it and cranking... $@#$%$#% - really not sure why I thought of doing that this time....

[Frank Beck]

Oh you DIY’ers...

By posting this plea for help you do know there’s a catch, right? You HAVE to tell us what the cause ultimately was, no matter what kind of stupid thing you did.

Pull off the lead again to see if you have spark jump between coil and coil wire when cranking. Most likely not coincidental and is related to something you’ve touched. If no spark, check primary lead for corrosion on both ends. After that see if you’re getting spark right at the points with cap off and key on. Move the points open with a screwdriver or your MacGyver pocket knife.

BTW: No need to disconnect ign sys to “build pressure”. Draining the sump does not lose the oil pump prime.

[edmayo]

When you disconnected the "coil distributor lead" did you pull the coil wire from the center of the coil and leave it hang ? or did you pull the lead from the center of the distributor cap and ground the end so the high voltage had some place to go ? If you did the first one then the high voltage had no place to go and may have found it's own path which could damage either the CD box or the coil, not always, but could have. Perform the second test, remove wire from center of distributor cap, laying the coil wire end against the coil bracket with a little gap to ground, crank engine, see if you get a spark.

[Greg D.]

Frank, no worries there, self deprecation is my specialty...
Ed, yes, and thank you for the reply... I initially disconnected the lead from the coil and let it hand from the distributor, really gave power it nowhere to go. When I replayed this in my mind I realized it is an open circuit and I probably trashed the coil or permatune... I have no idea why on earth I chose to do that, I never bothered before in previous CDI cars...
As it is, I have 12.6V at the permatune connector, and no spark coming off the coil at all... I fried either the coil or permatune, I cannot tell...I will look for a replacement test coil... I understand its hard to measure permatune output... I already ordered a replacement, worst case I'll return it...

I'll live... Prior to this I did a mini service on my 991 and saved the same amount that I just threw away being stupid.. And before Frank ask, no, I didn't screw the 991 up, it's all plastic bits and connectors ;-) You guys would laugh at what it takes to change the oil on that - plastic cover after plastic cover !

[62S-R-S]

...I fried either the coil or permatune, I cannot tell...I will look for a replacement test coil... I understand its hard to measure permatune output... I already ordered a replacement, worst case I'll return it...

I'll live...

A tremendous amount of disruption for such a benign maneuver of pulling the lead..there should be a 2 page 'achtung' in the glovebox manual for preventative purposes.

[Greg D.]

Good news: fixed it...

I fried the coil. And the coil only... I bummed a spare coil from my local mechanic (whom I subsidize greatly for other jobs) and boom, runs perfectly... I ended up buying that used coil for a song and brought him a bottle of wine for his trouble...

Lesson learned, this ain't a 912... don't mess with CDI ignition.

[edmayo]

Thanks for the good report!

[M_deJong]

Next time just disconnect the points wire from the distributor. Then the CD won't know its supposed to discharge.

[Greg D.]

Next time I simply won't bother unplugging anything... It's not really necessary apparently...

The 72 is a PITA for oil change jobs though... Because the last 2 oil changes were done during shop work, I forgot the 72 tank location makes it almost impossible to put my oil pan there, and reach the tank bolt without taking off the rearwheel, which means getting on the lift...after I'd already drained the case... ;-) I need to trade it for a 356, this is too modern for me!
Still, when you refill it, you know where you stand right away level wise...

On the modern 911, it took the computer 2 full days to confirm that I had added enough oil. (requires a dance of correct temperature for x-time, correct RPM for a certain time, correct angle, rub your tummy while patting your head kinda thing). Wish it still had a dipstick - 2 freaking days of driving it before it finally agreed to let me know ! maybe the dealer can cheat with Piwis and they do it on purpose to dissuade us...