Hi all,

It's been a while since I posted, but here is my question:

I have code 27, and a steady miss (or two)
While working on the engine I discovered that the number 4 and 5 injectors were not working.

I got number four to work by jumpering it from # 2.

I would like to jumper #5, but what is the appropriate injector # to jumper it off of. I plan to replace the PCM soon but I'd Like to see if I also need to replace the number 5 injector or just the computer.

In reality I may replace all the injectors as well as the PCM, but that will take me a while to get to and I want it to run as good as it can until I get to them

Any help is appreciated,
thanks,
Brian

 

What wires did you jump #5 to #2? Ground? Power? The Ground is provided by the PCM, the power is shared in between the injectors. My guess is that the power splices may be bad.

 

I tried jumpering to 6, but that didn't seem right to me. All wires ohmed good before I tried the jumpering.

I have been jumpering from power in all cases. I had just read that the injectors were batch fired, but I am not sure if that means they all fire at once or if not what the batches were.

 

The Magnum motors are Muliti-Port Sequential fuel injection. Common Power/Positive supplied by the ASD relay, individual Ground/Negative supplied by the PCM.

So if all your doing is splicing the power wires together, the factory power splice must be bad.

Here is a quick Google search on the definitions.

 

So I must have had my dummy goggle on earlier, I was thinking I had tapped into the power wires.

Just to remove any confusion:
I have NOT spliced the green wire with the orange (or pink whatever it is I cannot remember) that is commonly connected to all injectors; instead I spliced the wires that are individual colors and have dedicated runs back to the PCM.

I had those as the power in my mind, but they must be the individual grounds?

So if this is the case, (I do have the 3.9L Magnum with MPFI) then I take it from your post above that they are not fired in batches, but individually.

 

So I jumpered 5 to 6 since the injectors are fired sequentially and the truck is no longer missing. I am now thinking that it's the PCM for sure, since the wires all tested good for continuity back to the plug that goes into the PCM, and the injectors are all firing now.

Though the touch test tells me that the two that I thought were bad are not firing as hard as the good ones, so I will eventually just replace all the old injectors in the system (2 are new).

EDIT:
After replacing the PCM, the truck runs fine now. One thing that did happen was that while testing the wires for continuity, I accidentally bent the female cable ends that plug into the computer (PCM) so that they did not make sufficient contact with the pins when the plug was plugged into the PCM itself. This caused a miss, but once I figured that out and used a pair of very thin long needle nose pliers to reshape them, everything worked fine.