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More cars than sense
Join Date: Apr 2006
Posts: 1,726
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1977 2.7 CIS - No spark on crank, spark on run
Trying to track down an issue on my '77 911. Car was running and driving when I bought it but has been sitting for about a year.
The car has no spark when cranking but does have spark with the key in the run position. Verified by pulling a plug lead to see the spark. When we're cranking, there is no spark at all. But when we stop cranking there is brief spark as the car briefly turns over before stopping with the key in the run position. Seems like I've read about this issue before. Anyone have any ideas for me? |
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08-10-2018, 04:07 PM
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Could be low or no voltage getting to the CDI during cranking, maybe even a low battery.
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77 911s 16 981gts |
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08-10-2018, 04:42 PM
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More cars than sense
Join Date: Apr 2006
Posts: 1,726
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Battery fully charged and tested with a second battery.
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08-10-2018, 04:43 PM
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Registered
Join Date: Dec 2004
Location: PA
Posts: 1,162
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You should have power going to the center pin on the CDI .if it's a Bosch 3 pin
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08-10-2018, 05:40 PM
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More cars than sense
Join Date: Apr 2006
Posts: 1,726
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Car has a blue Permatune which I believe to be factory (little known fact, Porsche installed Permatune units at the factory on some cars in the 70's). Still a three wire connection. I'll check the power at crank tomorrow.
Any other ideas? Last edited by maninblack; 08-10-2018 at 05:57 PM.. |
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08-10-2018, 05:47 PM
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Join Date: Dec 2004
Location: PA
Posts: 1,162
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Have you checked the coil?What kind of coil do you have?
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08-10-2018, 05:52 PM
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More cars than sense
Join Date: Apr 2006
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Bosch coil. Assuming coil is good as I have spark with key in the run position.
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08-10-2018, 05:56 PM
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maninblack,
When you are running the starter, there is a separate path for +12v to power the ignition. It is the yellow wire attached to the starter. Could yours be unplugged? It also powers the Thermo Time Switch and the Cold Start Valve.
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Rex 1975 911s and 2012 Range Rover Sport HSE 1995 BMW R1100RS, 1948 Harley FL |
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08-11-2018, 06:46 AM
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More cars than sense
Join Date: Apr 2006
Posts: 1,726
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Got it guys. Break in a wire from battery. Thanks for the help.
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08-11-2018, 08:42 AM
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Excellent, glad it worked out for you- which cable?
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Rutager West 1977 911S Targa Chocolate Brown |
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08-11-2018, 10:28 AM
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1977 S
981gts
1975 Porsche 911s
1977 Porsche 911S Targa
