MoparAl

Hi guys, my names Al and a Ford man through and through. I've got an Escort RS2000 and recently a Jeep with a new Sierra based chassis and a 2.0i Dohc fitted. The engine has sat in the jeep for over 15years and never run.
I've managed to sort out the wiring to the best of my ability and managed to get her started but it's running well bad, when pulling plug leads off only one makes any difference. This is what I've diagnosed today.
Established 12v to all injectors.
With 12v at injectors I connected an earth to each one and heard them opening.
Disconnected ECU wiring block and checked for continuity between ECU wiring connector to each injector plug. It's here that it went weird as I not only had continuity on the earths in the connector block but also on the pin that goes to the 12v positive side of the injector plug ?
If I turn on the ignition and pull the plug of no.3 injector I get 12v at both pins on plug ? But if I pull the plug off no.4 injector and retest the pins on no.3 injector plug only the positive pin shows voltage ? Is this right or have I got an earthing of these cables somewhere ? I've never played with this type of engine before so excuse me if I sound daft.Al