TBI for dummies

[rfmaster]

Originally Posted by Nazzcu

Thanks rfmaster that was exactly what I needed. I still have one question that hopefully someone can clear up just for my understanding of the system.

Why straightwire the single injector? I plan to disconnect it and see what happens but I just dont get it unless it is another cut wire or bad circuit in the ECM.

It is hard to say what the hillbilly did but I venture to guess that one of the wires that provides +12 V IGN to the injector was damaged during swap. ECM acts as a grounding switch to complete injector circuit. When ECM grounds low side injector coil is energized and fuel is sprayed. So, one side of injector connector is tied to 12 IGN hot and the other side is pulled to ground by the switching circuit inside ECM.

Simple check - disconnect injector from injector, with ignition on (engine not running) one side should be +12 V and the other should read hardly any voltage on your trusty DVM.

Search guide to TBI swap on this board - there is a schematic of the injector circuit.

//RF