Hi Greg,
When I first noticed your post, it was the second page and I didn’t realize that there was a first page. So, I’ll now try to answer the questions that you asked there. Please keep in mind that with the addition of a turbo this project has evolved over the past 20 years and I may be a little rusty on some of the initial details before I added the turbo.
I think you may be confused about the fact that initially I did not use the ECM to control my ignition. I used my original ignition only along with an MSD 6A ignition box. This is all you need for the ECM to control fuel injection. The MSD 6A ignition box is needed to provide a square wave signal to the ECM. The ECM can only detect a square wave signal and needs to know the engine RPM to determine how often to fire the injectors. So, you don’t need the GM ignition module. I included it in the write-up as an option if you want the ECM to control both fuel and ignition. Initially I used the ECM to control only fuel and for that reason the GM ignition module it is not shown in the wiring diagram. It wasn’t until I installed a turbo that I used the GM ignition module and had the ECM control both the fuel and ignition. That would be a different wiring diagram.
As far as the potentiometer in the temperature sensor circuit, I did use that for a number of years. Mostly because I had no place to install the GM temperature sensor. The Chrysler sensor has a different temperature vs resistance curve than the GM sensor and would not work with the GM ECM. However, I later installed a larger radiator that had a location for a sensor in the top tank. I used that for the GM sensor and found that the car started quicker when hot. It was always a bit of a guess where to set the potentiometer.
I don’t know anything about the VN/VP Commodores 3.8L V6's. However, if it doesn’t have a MAF sensor you then have a speed density set-up and would have to program the ECM on the donor car for it to run properly with a SL6. If it is a speed density ECM it won’t work with a MAF sensor.
For the ground wire from the MAF sensor just run one wire to ground but also ground D1. Then connect D1 to D3, D6, D7, D10, D12, D13. A12 and B3 are also connected to ground
The oil pressure switch is a fuel pump safety switch. In this application this switch does not serve as a safety switch. It does not turn the fuel pump off with a loss of oil pressure. The ECM performs that safety function because it turns the fuel pump off when it no longer senses a tach signal. Rather, this switch keeps the fuel pump running in the event that the fuel pump relay fails, and in this way takes the place of the oil pressure switch that GM used in parallel with the fuel pump relay for this purpose. This is a “belt and suspender” approach and is good insurance. You can imagine what would happen if you were on the highway, in the passing lane, when the relay failed and you didn’t have this back-up system. Of course, if the fuel pump relay were to fail you would not be able to start the car again once it was turned off. I used a Mr. Gasket fuel pump safety switch from Jeg’s (
www.jegs.com) P/N 720-7872, $20. And yes, it has three terminals.
The fuel injector harness has three wires going in. One wire from the 12-volt source and the other two from the ECM. On the other side of the harness six pairs of wires go to the injectors. One wire in each pair is 12-volts so there is always 12-volts applied to each injector. The other wire at each injector goes to the wires coming from the ECM which are either grounded or not. The ECM internally makes and breaks ground depending on whether the engine is running and at a rate dependent on the engine RPM. The injectors are fired alternately in groups of three.
The pin out of the ECM is shown in the write-up just before the wiring diagram.
The turbo injectors are Bosch P/N 0-280-150-218
The breather just goes to atmosphere.
I hope all of this helps.
Bob D
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