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

 

the yellow/black or red/black wires should have batt voltage with the key on

the wires coming out ecu are signal/ground wires

 

They are ground wires, the reason you see battery voltage is because the injector doesn't stop the voltage from going through to the ECU. It's the ECU injector drivers that stop the voltage from going to ground / completing the electrical circuit.

Engine not running
Start [battery]--->----12v--->---[resistor]--->---12v / 3ohms---->----[injectors]--->---12v / 3ohms---->--- [ECU / injector circuit open]----->-----0v---->----[to chassis ground] Finish

OR

Engine running
Start [battery]-->---12v--->---[resistor]--->---12v / 3ohms---->----[injectors]--->---12v / 3ohms---->--- [ECU / injector circuit pulsing]------>------12v---->----[to chassis ground]

Not sure if that makes any sense to you or not......

 

yes it does, 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.

 

OK so your seeing 14v from the resistor to the injector even during the misfire. At the same time you are seeing 7v at the clip during the misfire. I'm guessing if you see 14v to the injector then the 7v is after the injector on the ground side. If that is the case I would suspect that there is a short/open in that injector or the clip. Have you tried swapping a different injector or a new clip in that position?

 

Yes I swapped out injectors same problem only cylinder 2, I think its a ground problem cuz now the red wire(which comes off ecu to injector) isn't supplying ground at the clip, but is supplying ground right out of ecu so I have an open in that wire, hope that fixes it, I'm gonna replace tonight