TvLover

OK, I have a GM 8 pin Computer controlled Dist. and I am trying to connect it to a older Holley EFI system. I contacted holley and I was told to connect the harness like this.
8 Pin GM HEI module connections (Direct from Holley) For the MPI Projection ECU
Blue /White Pin E on module
Yellow / Black Pin R on Module
Red +12Volts Pin B on Module This is the BYPASS pin on the module
Black Ground On Module


I agree with everything Except Pin B this shows as a 5 volt reference above 600 RPM not 12 Volts constant

I am attaching the PDF of the Manual for the Fuel Injection, Look at the last page for the Schematics, and the photo of the adapter for the GM dist. Holley Part number 534-47

Please tell me what is correct.....
I feel if I connect 12 volts to that terminal it will damage the module.

Six_Shooter

iTrader: (2)

You can use ignition trigger to switch a relay and use the 5V ref out of the ECM to feed through the relay to the bypass input. If you have the option I would use an extra output (if there are any, I'm not familiar with the Holley system) to trigger this relay/bypass input. Typically setting it to turn on above about 400 RPM is good. This causes the engine to start on base timing of the dizzy with no influence from the ECM, then ECU controlled timing above the RPM set.

TvLover

So I was correct and Holley was incorrect about the +12 volts on that pin. OK I feel better knowing I wasn't loosing my mind. I can easily feed +5 Reference into that pin from one of the other sensor power wires.

But if that IS the case Why would they sell that adapter and wire that pin to +12?

Six_Shooter

iTrader: (2)

The ICM may be fine with 12V, but since GM never applied 12V to that pin (that I know of), I'd not do it either.