cygnusx1 Posted September 7, 2011 Share Posted September 7, 2011 (edited) So I got the L28ET urbo swap running well in the '77. I spent a good part of the day wrapping up harnesses, routing and tucking wires. I buttoned up the electrical portion of the job and decided to check the running voltage at the coil transistor as a final measure. With the car running, I probed the positive lead and measured 13.4 volts, and just then, my butterfingers took over. The probe of my multimeter slipped from the post and jabbed the across to the other post on the transistor. The car instantly shut down and won't spark anymore. I assume I fried the transistor. I still get ign+ 12volts to the transistor, but no life from the coil and no tach signal anymore. The injectors might still be firing, I think.... The ECU still turns on and I tried another ECU just in case, but it made no difference. By jumping 12v to the other post on the transistor, would my "fried transistor" guess be correct? Edited September 7, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted September 8, 2011 Share Posted September 8, 2011 (edited) the small yellow wire fires the transistor by driving it to ground.If you connect a led to v+ and the other side to the yellow wire it should flash while cranking.If you have to you can use an early 4 pin gm hei chip to replace the transistor.or a bosch ignitor .I sold all of my old zxt stuff . Edited September 8, 2011 by randy 77zt Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted September 8, 2011 Author Share Posted September 8, 2011 (edited) I'm pretty sure the transistor is shot. I have another one I'm picking up tomorrow. I can't imagine anything else is damaged...I hope the dizzy didn't take a hit too. Basically, I accidently jumped 12v over to the spade that has a wire going back to the ECU for firing the coil. Edited September 8, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
FricFrac Posted October 10, 2011 Share Posted October 10, 2011 The ignitor transistor is expensive. Just do the four wire HEI install instead.... Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted October 11, 2011 Author Share Posted October 11, 2011 I bit the turkey and bought a new unit from Rockauto. $75. It worked. Quote Link to comment Share on other sites More sharing options...
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