the common wire to all of the injectors, where does it go?
I am wiring up obd1 in my ef hatchy that started as a dpfi

the yellow wire in common with all injectors, is this a common ground or a common power? how shall I hook it up?

 

The common wire for the injectors (yellow/black) is power. These wires connect to an 8-wire connector that will be situated where the injector resistor is on an SI (on the driver's side in the back). You can connect this two one of the two yellow/black +12 volt wires that went to the original DPFI injectors. Or beter yet, run a wire from the ECU power at the main relay to the 8-wire connector (this is how the SI and 1992-1995 cars are wired, and the fuel pump will not drag down the voltage).

 

I thought that with the obd1 ECU you didn't need the resistor box?

 

the resistor box is based on the injectors you use. Peak/hold or saturated. It doesn't matter the ECU it matters the ohms the injectors are.