Reversed battery connection - engine smoking

[uwanna]

Originally Posted by Porboynz

Bendix gear? That's a name from the past. I guess you could call the 911 starter clutch mechanism a Bendix but my memory of a Bendix is that it uses a course threaded sleeve and centripetal force to throw the starter gear into the flywheel ring gear when the starter shaft spins up. Crash smash and bash. The 911 starter is slightly more civilised with a solenoid pre engagement of the starter gear on a sliding sleeve incorporated with the clutch mechanism for those who keep cranking after the engine has fired. Could be wrong, I seem to remember the Bendix mechanism had a huge spring that would break when you least expected it and then would not disengage from the ring gear and make a real noise. Any volunteers to see if a 911 starter does run backwards? My bet is not and if it did the clutch would prevent it from turning the engine over. Sorry for hi jacking the thread, none of this is helpful, but it is interesting, sort of.

Yea, Bendix is an old term. Tirwin and I (Grant) were discussing whether the starter could turn the engine over backwards with reverse polarity when we installed a new Hi Torque starter. There was a Pelican from Europe who claimed he installed an Ebay Hi Torque starter and it turned his engine backwards and it caused major damage including bent valves among other things.
In our discussion we surmised that it probably couldn't turn the engine backward, due to the "one way' clutch on the starter gear teeth. I still cling to that hypothesis, but will remove Bendix from my Porsche starter lexicon. LOL

[Avanti]

Originally Posted by Porboynz

Bendix gear? That's a name from the past. I guess you could call the 911 starter clutch mechanism a Bendix but my memory of a Bendix is that it uses a course threaded sleeve and centripetal force to throw the starter gear into the flywheel ring gear when the starter shaft spins up. Crash smash and bash. .

Its generically called a Bendix drive on modern starters and has a form of an overrunning clutch. The "crash smash" type you describe is called an "inertia drive" starter mechanism which have not been used in many years. I had one on my '41 Lincoln Continental Cabriolet V12.

[timmy2]

Venezia,
You may have melted the insulation on the yellow wire from the ignition switch to a red power lead at the ignition switch or anywhere from the switch to the solenoid.

Could be the wiring in the starter is shorted .

Pull the yellow wire off the starter solenoid and see if it still wants to turn over.

If not, then connect it back up and disconnect the single plug yellow wire connector near a 6 pin plug that goes through the sheet metal near the ignition switch under the dash on the trunk side and try again.

If it doesn't try to start with that wire unplugged, the problem is likely in the ignition switch or small wiring lharness to it.

[timmy2]

Any updates? Or is it in a shop now?

[Venezia]

I pulled the 14 pin connector and switched on the battery - starter motor engaged but no smoke! Have a flat bed coming tomorrow and will be in the hands of a good 911 wrench by mid day. More to come.
Thanks to all for your feedback and also special thanks to all who have served our country!

[JFairman]

If you need a new alternator they don't come any better than this... I have one and it's amazing.
Good luck with it.
Porsche 911 Alternator 1984 1989 High Amp 160 Amp High Output Generator | eBay

[N11Porsche]

I did this on a BMW Z3 roadster. Alternator fried, Alarm module fried, BMW version of the DME, fried. Had the work done at an independent shop. Total damage over $4k.

[timmy2]

Starter turning with 14 pin connector disconnected probably means melted wires in the engine harness have shorted.
Likely the Red wire melted to a Yellow one.

PM or email me if your wrench tells you that you need a new Engine Harness.

[rick-l]

Probably this one

Pelican Parts - Product Information: 930-607-016-02-OEM

I wouldn't buy a new one just get out the soldering iron and heat shrink.

[T77911S]

Originally Posted by Venezia

I pulled the 14 pin connector and switched on the battery - starter motor engaged but no smoke! Have a flat bed coming tomorrow and will be in the hands of a good 911 wrench by mid day. More to come.
Thanks to all for your feedback and also special thanks to all who have served our country!

unless you removed the rellow wire from the starter, then i bet the alt battery cable melted to the starter wire.

[Venezia]

Here is the update.
The red and yellow wires from the starter are melted together.
Question - does the engine have to get pulled to replace them?

[rick-l]

It depends....

More info is needed. There are three red wires going to the alternator. A 10 mm^2 wire (~8 AWG) that stands alone (not in the harness with the 14 pin connector) and goes to the starter and two 2.5 mm^2 wires (~14 AWG) that go to the engine compartment fuse panel.

So did the big wire melt through the wire harness to get to the yellow wire or did the smaller red wires melt inside the harness to get to the yellow wire? The later seems unlikely since they are fused.

[timmy2]

The 2 smaller gauge red wires in the engine harness are not fused in the harness, they connect directly to the main feed from the starter at the alternator and are crimped in the same comnector.

[Venezia]

I found an excellent 911 mechanic who got the car back on the road. The wires from the starter back to the alternator were fused together, alternator was toasted, and many wires leading from the alternator back to the engine harness, etc we destroyed. Starter, DME we okay and new splices were made to the damgaed wires and alt. was replaced. Have driven the car approx 100 miles and have some good and bad - good is the car seems to be more powerful than before, radio is clearer and louder; dimmer on instrument lights has more gradients and is brighter; bad is the windshield wipers wont turn off ( so I pulled the fuse and will try to diagnose the issue). An expensive dumb ass move but happy to be flying again inmy 911. Thanks for all for their contributions - Happy Porscheing!

[porsche930dude]

hope youre keeping a fire extinguisher in the car close at hand. sounds like youve still got some melted wires in there somewhere

[rick-l]

you could disconnect the wiper intermittent relay and see hat happens.

[timmy2]

It can get real bad reversing the polarity.
This 3.2 harness was sent to me to make a new one.