Greetings,
I installed aftermarket audio system when I purchased the truck but only recently noticed an issue with the charging system, dash gauge dropped to 9V and the A/C blower stopped. I turned A/C blower fan off, music off, and continued driving with headlights only. The fan came back on when attempted but I continued my night commute with no music or air to keep load off the charging system. The A/C blower fan later began to intermittently fail before failing to come on at all. I've since swapped the A/C relay, resistor, and blower motor. A/C blower fan failed to power on but the clutch would still engaged when the A/C was turned on via climate controls. Thinking it was a grounding issue, I replaced the grounding strap from the body to the frame and added one from that point to the transmission case, as the strap to the engine block appeared ok and was hard to access. I took the truck for a test drive and noticed significant improvement to ~13.8V at the dash gauge, with music and lights on. However, although the A/C blower fan still wouldn't power on, A/C clutch now no longer engaged when turned on via climate control. I parked the truck for the night, went out the next morning to start it, crank no start.
After two weeks of troubleshooting and scouring the internet, this forum (as a non-member), and my Chilton, I've replaced the Fuel Pump, Fuel Filter, cleaned the Tank, rebuilt the TBI (with kit), replaced the Distributor, cleaned all Grounds, and replaced the battery. I believe that I've traced the issue to a lack of power at the ECM. Why there is a lack of power, I do not know.
On my ECM unit, two pink wires, F15/E15 should have +12V with the key in the on position. These wires are fed +12V from the 20A ECM-I and ENG-I fuses in the Relay Center, respectively, located under the hood. When I measured voltage at the ECM, with key in ON position, ENG-1 reads ~7.3V and ECM-1 reads ~10.3V. So I spliced then connected F15, E15, and the pink injector wires directly to the +12v post on the battery. The Fuel Pump primed, the engine successfully started and entered closed-loop idle once warm. I then checked for voltage drop between +12V post on battery and Relay Center and got consistent ~12.38V readings. With the +12V battery post disconnected from the truck, I ran a wire directly from +12V post on battery to the other end of F15 in the relay center and tested voltage at the ECM again. It read battery voltage of 12.38V. Using continuity tests, I ruled that ENG-I (E15) was being grounded (only while the Heated O2 sensor was connected) so I did not perform battery to relay center test on the other end of E15 for fear of shorting a wire or component. I then reconnected my splices using solder and shrink wrap, disassembled and cleaned all connections in the Relay Center before reassembling it all with dielectric grease, disconnected the Heated O2 sensor, reconnected the +12V battery terminal, then attempted to start the engine. Crank no start. So I checked voltage at the ECM on F15/E15 and they again read ~10.3V and 7.3V respectively. At the time, I did not check for grounding on ENG-I (E15) because the Heated O2 was/is still disconnected. I then removed the ENG-I and ECM-I fuses from relay center and jumped pins F15/E15 to the cigarette lighter +12V, with multimeter attached. I heard the fuel pump prime, the engine started when I attempted, and the voltage at pins F15/E15 rose and stabilized at ~13.8. The engine successfully entered closed-loop idle once warm and had no issues idling with several wraps of the throttle. I figured I had nothing to lose then, so I plugged the ECM-I and ENG-I fuse back in to see if it caused a short. There was no change in engine RPM and no fire or smoke. When I removed the wire from the cigarette lighter +12V, the engine died. I can repeat this process on-demand and though not yet driven, with the exception of the A/C blower not working, engine and charging system appear fine once the engine is started.
At this point, does it make sense to just run two new wires from the fuses?
I installed aftermarket audio system when I purchased the truck but only recently noticed an issue with the charging system, dash gauge dropped to 9V and the A/C blower stopped. I turned A/C blower fan off, music off, and continued driving with headlights only. The fan came back on when attempted but I continued my night commute with no music or air to keep load off the charging system. The A/C blower fan later began to intermittently fail before failing to come on at all. I've since swapped the A/C relay, resistor, and blower motor. A/C blower fan failed to power on but the clutch would still engaged when the A/C was turned on via climate controls. Thinking it was a grounding issue, I replaced the grounding strap from the body to the frame and added one from that point to the transmission case, as the strap to the engine block appeared ok and was hard to access. I took the truck for a test drive and noticed significant improvement to ~13.8V at the dash gauge, with music and lights on. However, although the A/C blower fan still wouldn't power on, A/C clutch now no longer engaged when turned on via climate control. I parked the truck for the night, went out the next morning to start it, crank no start.
After two weeks of troubleshooting and scouring the internet, this forum (as a non-member), and my Chilton, I've replaced the Fuel Pump, Fuel Filter, cleaned the Tank, rebuilt the TBI (with kit), replaced the Distributor, cleaned all Grounds, and replaced the battery. I believe that I've traced the issue to a lack of power at the ECM. Why there is a lack of power, I do not know.
On my ECM unit, two pink wires, F15/E15 should have +12V with the key in the on position. These wires are fed +12V from the 20A ECM-I and ENG-I fuses in the Relay Center, respectively, located under the hood. When I measured voltage at the ECM, with key in ON position, ENG-1 reads ~7.3V and ECM-1 reads ~10.3V. So I spliced then connected F15, E15, and the pink injector wires directly to the +12v post on the battery. The Fuel Pump primed, the engine successfully started and entered closed-loop idle once warm. I then checked for voltage drop between +12V post on battery and Relay Center and got consistent ~12.38V readings. With the +12V battery post disconnected from the truck, I ran a wire directly from +12V post on battery to the other end of F15 in the relay center and tested voltage at the ECM again. It read battery voltage of 12.38V. Using continuity tests, I ruled that ENG-I (E15) was being grounded (only while the Heated O2 sensor was connected) so I did not perform battery to relay center test on the other end of E15 for fear of shorting a wire or component. I then reconnected my splices using solder and shrink wrap, disassembled and cleaned all connections in the Relay Center before reassembling it all with dielectric grease, disconnected the Heated O2 sensor, reconnected the +12V battery terminal, then attempted to start the engine. Crank no start. So I checked voltage at the ECM on F15/E15 and they again read ~10.3V and 7.3V respectively. At the time, I did not check for grounding on ENG-I (E15) because the Heated O2 was/is still disconnected. I then removed the ENG-I and ECM-I fuses from relay center and jumped pins F15/E15 to the cigarette lighter +12V, with multimeter attached. I heard the fuel pump prime, the engine started when I attempted, and the voltage at pins F15/E15 rose and stabilized at ~13.8. The engine successfully entered closed-loop idle once warm and had no issues idling with several wraps of the throttle. I figured I had nothing to lose then, so I plugged the ECM-I and ENG-I fuse back in to see if it caused a short. There was no change in engine RPM and no fire or smoke. When I removed the wire from the cigarette lighter +12V, the engine died. I can repeat this process on-demand and though not yet driven, with the exception of the A/C blower not working, engine and charging system appear fine once the engine is started.
At this point, does it make sense to just run two new wires from the fuses?
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