Expert: Jim Holsbeck - 9/11/2007

Question
I have a 1993 Suburban, 4X4 K2500 with 7.4L TBI. I have had an ongoing issue with the ignition system. The engine will start and run for about 12 to 15 minutes then stop. If I try to start it, it will turn over but will not start. I am not getting any spark out of the coil. I have also noticed that the fuel injectors are not firing. If I replace the ignition control module, the engine will start and run again for about 12 to 15 minutes then turn off and wont start until I replace the ICM again. I have replace the fuel pump, fuel filter, fuel regulator, the distributor, coil, wires, plugs, and ECU. The ECU has a Jet Performance Chip in it. I have also replaced the alternator and have a good consistent 14.4V at the battery. I also installed an electric fan on the radiator. I'm very puzzled as to what would cause my ICM to keep going out. Could it be a bad ground, high/low primary/secondary voltage?

Answer
Mark,
    The first question I would have is did the problem start when you installed the performance chip? If not, then I would say you have a wiring problem. I would check the voltage you have at the ICM when it is running and see if it drops off or surges. If you are blowing ICMs after 12 to 15 minutes, there is definately some problem in the wiring, whether it be a short or surge. If the problem started when the chip was installed, I would uninstall it and see if it helps.