i have a quick question you guys. the wires that come off the ecu and go to each injector, for example obd0 mpfi a1,a3,a5,and a7 obd1 A1, A3, A5, A2,.....are those wires grounds or power wires? reason i ask is because i know in manuals it tells you to check voltage between each prong in injector clip to see if you get batt voltage, and if you do that with ignition on, you do get battery voltage, but if you check for battery voltage using those prongs as positives and you another ground you also get batt voltage at those pins when ignition is on, which doesnt make sense to me cuz i thought they were ground wires. can any body explain this please

 

they are grounds technically. 12V goes to the injectors from the main power supply, to the resistor box, then to the injectors. then a wire goes to the ECU and then a transistor (i think thats what it is) switches to ground it when it needs to send fuel

 

right, the computer supplies a ground to the injectors to complete the circuit when it wants the injectors energized

 

the reason i ask is on e of my injectors intermittently will not function right and when i check voltage at clip during the misfire, i only have 7V there while the other clips have 14V, but the wires coming out of resistor to injectors all show 14Vs, so i wasnt sure if i had bad connection between injector and resistor or, injector to ecu(bad ground). cuz when i use battery ground as my ground and check for voltage at the connector i get good 14V. but not when i use connector ground.