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Bosch ignition problem 700 1989

posted by  someone claiming to be jmarsnc on  Sun Feb 17 05:46 CST 2008 [RELATED]

Thanks for the input. I have done the trace back you suggest and it leads back to the power Stage/ECU. Of note was the fact that the ignition ECU was not sending a signal to the FI ECU to turn on the fuel pump. The problem is how to get past this point. The ECU sends a signal to the power stage as to whether or when to ground the coil (and tach) In this way the ECU can respond to the knock sensor to retard the spark. The amount of retard is limited by the width of the rotor contact (note that it is wider than older ones.). Of note also is that the ECU operates at 5v whilst the coil operates at 12v. Since replugging the power stage will often cure the problem for a while, it suggests to me that the culprit could be a capacitor that needs to discharge. You might look at Goatman's post for more info. I found a download for a Volvo greenbook on the ignition that I need to print and digest.






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