Classic/Antique Car Repair: Wiring harness, auto electrics, mg autos

Question
Brian,

This is a general electrical question that relates to the wiring harness.

I am not getting the electric signal to one of my cylinder ejectors(of 6).

Do I replace the entire wiring harness(age 25 years) or look in another area first?

Note- I swapped the CPU/main computer, and it made no difference.

Answer
Bill:

I generally limit my answers to MG autos, but in this case I'll try to give you some info that may be of use.  First, just because the car (and harness is 25 years old is not necessarily a reason to replace it, unless you are talking about the underhood harness (if it is seperate) only. If you have a seperate underhood / engine compartment harness, then yes, it could be ready for replacement due to the heat, etc.

As MGs don't have fuel injectors, I have limited experience with them, however I suspect you may simply have a bad injector which needs to be replaced. It can get very expensive and time-consuming to start swaping out parts without first determining what the problem is...you may not have needed the CPU/main computer. If you know the injector is good, then check the harness / wires for that injector. The first rule of auto electrics is this:  Wires themselves RARELY fail (unless they are cut or melted so they short out. Connectors or connections frequently do due to dirt. oil, vibration causing looseness, etc. Check all the connections and grounding points. Make sure you have a signal to the injector measured at the injector connector. If you get a signal to the connector - then you have a bad injector.  If you can't get a signal to the injector connector, then trace that particular set of wires BACK to the point where you either find the problem or you actually get a reading/ signal.  Good luck.

Brian