1988 Chevy Truck V8 Four Wheel Drive Automatic
I wondered if anyone could help me with a question that I can not seem to get a answer to. I have a 1988 Chevy 350 TBI K1500 truck and need to know could a defective ECM cause it to have no spark. I have fuel out of injectors, power to the coil. I have replaced the coil, ICM and it has a whole new Dist as of 6 months ago. Timing is good also just set it and confirmed the rotor is turning when motor is cranked. Problem started where it would cut out and surge at low-mid rpm but if I gave it more gas to where it would go into passing gear it run really good, but as soon as rpms dropped down it would start surging and cutting again. Then I was getting on the freeway and to stop it from cutting out I gave it about 3/4 throttle and it kicked a couple times and shut off. Now it cranks fine but I have no spark. PLEASE IF YOU CAN GIVE ME YOUR THOUGHT ID REALLY APPRECIATE IT.
Thanks A lot
Welcome to the forum. Is there a pulse on the negative/tach side of coil, use a testlite? Any codes?
With bypass ignition, it is the ignition module that controls spark under 400 rpms. Over that, the ecm puts 5 volts on tan wire with black tracer. That signal tells the icm to use the signal on the white wire for spark timing. If signal on the tan wire and none on the white, there may not be any spark. Whether the problem is the wiring circuit or ecm?