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-   -   Two 79SC simple questions (http://forums.pelicanparts.com/porsche-911-technical-forum/148842-two-79sc-simple-questions.html)

OldTee 02-15-2004 09:01 AM

Two 79SC simple questions
 
One: I noticed a brown (propably a ground) attached to a lug under the fuel door. It was rusted and most likely not conducting. What is it and why is it there? Static elec path?

Two: putting new pads on I noticed that there were not keys holding the pins on the calibers. Instead there is a split sleeve on one end of the pin. Does this take the part of the keys or do I need to order some parts?

Bonus. While working under the left front fender I found that a great deal of dirt and sand had lodged under the airconditioning and w/washer hose that reside at the top of the fender. A sure source of rust. Blast the area carefully with a garden hose under pressure to dislodge it all.
SmileWavy

Great board. Thanks

PS I still don't know what the wire was under the left rear fender!

Mark Wilson 02-15-2004 09:17 AM

Quote:

PS I still don't know what the wire was under the left rear fender!
If it's at the back and wrapped around a brace, it's a lead for rear fog light.

makaio 02-15-2004 09:21 AM

The front caliper retaining pins do not have cotter pins, only the rears.

The wire in the rear fender area is for a rear foglight like Mark said.

As for the wire near the fuel door, I don't know.

Jim Sims 02-15-2004 09:46 AM

Brown wire under the fuel door is indeed a safety ground (to minimize the chances of a static electricity spark igniting fuel vapors); the metal fuel filler neck is electrically isolated without it. The fuel filler neck resides in a rubber collar and is connected to the tank neck with a rubber sleeve which would insulate it from the balance of the car. Polish up the lug and connector, coat them with silicone dielectric grease and reinstall snugly. Cheers, Jim

Formerly Steve Wilkinson 02-15-2004 10:27 AM

I don't understand. If the filler pipe is "electrically isolated" without the ground wire in place, how are you going to get a spark off it? I should think the brown wire, if it indeed grounds the filler neck, would thus make it sparkworthy.

Stephan

Jim Sims 02-15-2004 10:36 AM

Charge builds on the filler neck due to electrostatic induction; there is an electric field produced across the rubber. Energy is stored in this electric field and when discharged produces a spark. The metal filler neck is like one of the plates of a capacitor. The chassis of a car usually remains grounded as there is enough carbon black in the tires to make them semi-conducting to the pavement. This is the same problem as filling a fuel can in the bed of a pickup with a plastic or rubber bedliner- a charge can build up and produce a spark (in the presence of fuel vapors!) to the pump nozzle. Cheers, Jim

OldTee 02-15-2004 12:05 PM

Hard not to learn something on this board. ;)

Thanks


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