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abit off center
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Loosing spark with an andial splitter
Been chasing this problem. Starts up just fine, pick up the rpm to around 2500 its smooth then all of a sudden it shuts down. Sometimes it just drops spark for a second and catches again. After checking everything I can think of I decided to pull the splitter apart and found a loose capacitor joint on the board. All is good now!
 
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______________________ Craig G2Performance Twinplug, head work, case savers, rockers arms, etc. |
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03-06-2011, 02:37 PM
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Craig,
looking at this circuit you have a simple +5V power supply realized with an integrated voltage regulator (L7805) and a couple of resistors and a capacitor. The IC is a NAND Schmitt Trigger 4093 that is used to generate a signal inverse to the ignition pulse that comes out of the DME. Pin 1 of the DME must be the green wire. It goes to a 1kOhm pull-up resistor against the +5V power supply. That is the input of the Schmitt-trigger. Normally pin 1 of the DME is floating and that makes the input of the 4093 +5V and the output 0V. For each spark event pin1 gets pulled to GND. And that produces a +5V pulse on the output of the 4093. The output goes to the two white wires. So you must have two ignitors that are driven by the white wires, correct? The only reason I can see for the spark to disappear is that the L7805 gets hot due to overload and shuts down. This could be caused by a partially damaged 4093. The L7805 has an internal thermal protection and overload protection. But in that case the LED should also go out. Have you checked if the L7805 gets hot to the touch during operation? Ingo
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1974 Targa 3.6, 2001 C4 (sold), 2019 GT3RS, 2000 ML430 I repair/rebuild Bosch CDI Boxes and Porsche Motronic DMEs Porsche "Hammer" or Porsche PST2, PIWIS III - I can help!! How about a NoBadDays DualChip for 964 or '95 993 |
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03-13-2011, 04:23 PM
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OK, I should have read your entire post before answering..... I can see that a bad solder joint on the capacitor causes oscillation and that is what might have caused your issue. Good find.
Ingo
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1974 Targa 3.6, 2001 C4 (sold), 2019 GT3RS, 2000 ML430 I repair/rebuild Bosch CDI Boxes and Porsche Motronic DMEs Porsche "Hammer" or Porsche PST2, PIWIS III - I can help!! How about a NoBadDays DualChip for 964 or '95 993 |
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03-13-2011, 04:25 PM
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abit off center
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I jumped the gun!! That did not end up fixing the problem, could that have damaged something else?
I just sent you some information about his, I have replaced almost every part on the board but as you advised I am going to remove the splitter and try it without and see how it goes. Your help has been most appreciated!!
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______________________ Craig G2Performance Twinplug, head work, case savers, rockers arms, etc. |
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03-13-2011, 04:30 PM
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1969 and 1986 Porsche Targa and Coupe 1720cc and 3
1974 Porsche 911 Targa 3.6
