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CD Box 3-pin test. No Spark
Is there a good test for the 3-pin cd box to test spark or if the box is good? I am not getting spark and I am starting to think it is the box. It has been sitting on the shelf for 3 years and now I am ready to start the engine. My shop has checked everything to the cd box, they clame the coil is fine, points, etc. but no spark now. Any help would be greatly appreciated.
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11-23-2010, 02:24 PM
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Posts: 9,569
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what sound does it make?
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'66 911 #304065 Irischgruen ‘96 993 Carrera 2 Polarsilber '81 R65 Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13) Ex-'88 Carrera (Sold 3/29/02) Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04) Ex-'89 944 Turbo S (Sold 8/21/20) |
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11-23-2010, 02:26 PM
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It makes the whine that it is supposed to be making.
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11-23-2010, 02:37 PM
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A 3-pin box can be tested fairly simply; remove the 3-pin connector and run individual wires to it. Pin B (center) is +12 volts, Run a wire from pin A to the coil (the other side of the coil is GND) and then hook a wire to pin C. Connect a spark plug to the output wire of the coil via a high voltage cable and ground the spark plug.
Once you provide +12 volts to pin B of the box you should hear the 3kHz whining noise. Once you touch the wire from pin C to GND you should see a spark being generated.
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Rex 1975 911s and 2012 Range Rover Sport HSE 1995 BMW R1100RS, 1948 Harley FL |
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11-23-2010, 03:36 PM
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Location: Nash County, NC.
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Look at the harness from the CD to the coil and distributor. The white wire inside the sheild ground breaks down and leaks through to ground, thus no spark. Prove it by running alagator clips to each connection point on the coil and distributor. These wires started going bad 20+ years ago.
Bruce |
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11-23-2010, 06:08 PM
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I will begin testing now! Thanks
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11-24-2010, 08:51 AM
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Location: Portland, Oregon
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Does your shop have a known good CDI to plug in to test?
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Harry 1970 VW Sunroof Bus - "The Magic Bus" 1971 Jaguar XKE 2+2 V12 Coupe - {insert name here} 1973.5 911T Targa - "Smokey" 2020 MB E350 4Matic |
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11-24-2010, 12:41 PM
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It was a wiring issue completely! it runs great! Woo Hoo Thanks a million guys!
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11-24-2010, 02:48 PM
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Location: Portland, Oregon
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Hey, glad to hear it was simple!
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Harry 1970 VW Sunroof Bus - "The Magic Bus" 1971 Jaguar XKE 2+2 V12 Coupe - {insert name here} 1973.5 911T Targa - "Smokey" 2020 MB E350 4Matic |
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11-24-2010, 04:04 PM
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1975 Porsche 911s
