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72 911T no start

I pulled the plugs today to check their condition. They were sooty (not oily) so I cleaned them up and installed them back into the car. The car was running pretty well yesterday with a little backfiring.

While I was at it I pulled the rain hats off the air cleaners to peek inside the carbs. They looked pretty good!

Now the car won't start and I've go no spark. WTH?
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1978 SC Coupe, Gris Argent Metallic Silver
1974 2002 Tii Polaris Silver, Under construction
1972 911T
Old 10-12-2017, 01:24 PM
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check power (12v) to cdi box. Does it whine with ignition on?
Old 10-12-2017, 01:28 PM
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Fuel pump is running if that's what you mean. How does one check the CDI box?
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1978 SC Coupe, Gris Argent Metallic Silver
1974 2002 Tii Polaris Silver, Under construction
1972 911T
Old 10-12-2017, 01:30 PM
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Lack of high pitched squeal from CDI box with ignition on means dead box.
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Old 10-12-2017, 01:37 PM
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So the CDI unit just went on me...pure coincidence? I don't remember any 'high pitched squeal' before.
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1978 SC Coupe, Gris Argent Metallic Silver
1974 2002 Tii Polaris Silver, Under construction
1972 911T
Old 10-12-2017, 01:53 PM
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You can only just hear it in the cabin but quite audible in the engine bay. You probably don't listen in the engine bay with the ignition on very often!
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Old 10-12-2017, 02:01 PM
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Wont start

Go to your distributor, check points and small wire
inside on base,
You said day before was back firing, thats the sign bad points
condenser or very small gap on points.
Old 10-12-2017, 02:26 PM
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Quote:
Originally Posted by wayne robson View Post
Go to your distributor, check points and small wire
inside on base,
You said day before was back firing, thats the sign bad points
condenser or very small gap on points.
All true but he has no squeal so CDI box is a dead thing.
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Old 10-12-2017, 02:34 PM
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Quote:
Originally Posted by wayne robson View Post
Go to your distributor, check points and small wire
inside on base,
You said day before was back firing, thats the sign bad points
condenser or very small gap on points.
BINGO! We have a winner!

My buddy the Master Porsche mechanic walked me through the diagnosis by phone. After we checked all the wiring to the CDI and the coil, and the very high pitched noise coming out of the CDI box that I couldn't hear until I put my ear up to it, we moved on to the points. My hearing isn't what it used to be Johnny H.

While not easy to access, I managed to pry them open with a small screw driver, file them with a tiny file, spray them with brake clean and then blow it all dry with a small compressor. Bingo bango bongo it started right up!

Thanks to G. After hearing about my black sooty plugs, we'll be moving on to adjusting the rich running condition next. Feel free to weigh in on that!

Thanks everyone!
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1978 SC Coupe, Gris Argent Metallic Silver
1974 2002 Tii Polaris Silver, Under construction
1972 911T
Old 10-12-2017, 03:12 PM
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Great news

Bongo, Bango, Bingo.-------all good.
Old 10-13-2017, 02:46 AM
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Quote:
Originally Posted by Jonny H View Post
All true but he has no squeal so CDI box is a dead thing.
So buy my cdi+,
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72 911
Although it is done at the moment, it will never be finished.
Old 10-13-2017, 06:44 AM
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now that you have found the points are the prob, set them to 0.010" thou to start then set with a dwell meter to 38 +/- 3deg, a little bit of oil on the top of the distributor shaft while you are there (under rotor)
Old 10-13-2017, 07:57 AM
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point gap

Hi strictly, i disagree with your 10 thou gap that is to small ,should be set at
14 thou, i will tell you why.
Way back 20 years ago i owned a 69, 71 ,and 72 911, and i had a lot of experiance
on messing around with points on 911s.
Alot of service techs rely to much on dwell meter, they are ok with in reason.
What happens when setting on a small gap, the points dont wear as most techs think
and wear making the gap larger its the opposite, they wear making the gap smaller,
because of carbon,electrical high spots on critical points face,and other causing items
like bad condenser fitted , that should always be changed as well with points.
When this happens it can only take about 500 miles,and the car will end up with
5-6-7 thou gap.
Then car will start missing , hesitation, etc, after about 1to 2 thousand miles
wont even start.
Always fit good quality points of a good reputable make , years ago alot of
makers made vented points, these would only go about a thousand miles and fail
had small holes at the point face and caused bad wear because of the hole.
this may help others---regards.
Old 10-13-2017, 05:18 PM
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