Hi guys, I swapped a 5.0 into a 1983 Firebird that was previously a 2.8 V6. I did a very neat swap and kept the 5.0 CCC carbed, and I used all of the factory emissions equip correct for the 83 5.0. Here's the problem. The engine starts and runs on just the HEI module, but I found it was not getting a signal from the dist. The CEL is on solid all of the time. I tried to pull codes but the CEL just stays on solid (I tried unplugging the ECU and it didn't change the solid CEL, it looks like this means the ECU is not powering up). I tried a couple of known good CCC carbed ECU's and still nothing. I checked the 2 engine-harness grounds through the ECU pins with a multimeter and they are getting good grounds. The battery power at the ECU pins is also good at 12.8 volts. The pink/black ignition power wire at the ECU was dead on ignition on. Just for diagnostics I pulled IGN power off of the fuse block and spliced it into pink/black. The underhood sensors that have the pink/black wire (mixture control solenoid, egr solenoid, esc module, etc) now all show 12.8 volts at their power wire with the key on. However I still get a solid CEL, can't pull codes, and the engine starts and runs on base timing only, with no signal from the ECU. There were several ground ring terminals (I think 3 or 4?) in the engine harness that I made sure were grounded. Is there anything else that could be causing the ECU to not power up or do anything if it has both battery and ignition signals, and it has grounds? Sorry this isn't exactly a DIY prom burning post -- I burn proms with the 165 in the camaro. I figured this was the best place to ask a wiring question like this w/ the ECU since the TBI and TPI cars are similar to the CCC carbed at least in body wiring.

 

This is probably unrelated to your problem, but I'll mention it anyway incase it was overlooked. I don't know the full context of your previous 2.8L's wiring, but the CEL control line is inverted on the older stuff w.r.t. the new stuff. The white/green CEL control line goes to a green box which controls the CEL, the more recent ECM's control the CEL directly.

 

Monte' is correct that the "light driver module" that runs the SES is "high" to make the stay off.
Do you have the external ESC "module" in your system?
The older stuff ran timing from there and may be why the module is not coming out of bypass mode.

 

The ECU I am using for the V8 is an 84, so the CEL is run the same as the 83. I am using an external ESC module because I am using a 1984 ecu from an L69 high output 305-4bbl which had higher compression than the LG4. The timing is run off of the ECU. The ESC only intervenes if detonation is sensed (it deviates from its 10v signal it returns to the ECU during normal operation). My major problem seems to be that the ECU is not doing anything! Its driving me nuts because I took so much care to wire and plumb this car as a stock 83 V8 (I know, yuck, but I was curious).

 

The first diagram is a 1983 V6. The second is the 1984 V8.

 

I have full wiring diagrams and FSM's for the 83 and 84 V6 and V8s, from several different sources to verify validity. According to me reading the diagrams everything is wired correctly. I'm sure the problem is in the body harness where I took for granted something was wired correctly because the car was previously running with the ECU when I took it apart.