Chevrolet Repair: Chevrolet/GMC Suburban C1500 ignition problems, chevrolet gmc, power transistor

Question
QUESTION: I have a 1986 GMC (equiv to Chevrolet)Suburban C1500 2WD 350cc engine that now runs only once or twice between each ignition module it burns out. Plugs, wires, rotor, dist. cap and the module have been replaced over and over by mechanics but they never fix the cause. Please give me suggestions on how to track this down. What is left? Ignition coil, pickup coil, coil wire? Thanks much

ANSWER: Hey David,

 The only high load part of that circuit is the primary side of the ignition coil and thats probably what is burning out.  Have the technicians check the ignition coil ramping amperage on the primary side and I bet its off the charts.


Wayne Howie



---------- FOLLOW-UP ----------

QUESTION: Hi Wayne,
Thanks for the quick reply. Since I have to have the truck towed every time I try to have it fixed is it worth just replacing the ignition coil itself (I'm guessing I can do it myself-I used to work more on my vehicles until life got too busy) or might that not solve the problem. Thanks again.

Answer
Hey,

  Lets put it this way.  The ignition pickup sends a small voltage to the sense part of the module for ignition profile.  It is less than 2volts and as far as amperage is concerned its not even a measured amount.  The secondary side of the ignition coil isn't even physically connected to the primary side.  Its all done through coil saturation and magnetic field induction.  The primary side of the coil is controlled by the power transistor in the module and can exceed 10 amps under some conditions depending on the type of coil and primary winding resistance.  I would bet a small cow that the ignition coil fixes the problem.

Wayne Howie