.. it is a white wire in a black sheath on its own.. comes off the injector loom near the alternator.. is live ignition switched.. anyone knows what it is I would be really greatful... even if it isn't the reason my motor wont start..
O.K. Tigger lets get down to it!! Now, I have to make some assumptions here, you have a 3.9 on hotwire injection with DLM8 dizzy and a 14 CUX ECU. Your engine is a serpentine and mine isn't. I will assume the basic circuit layouts are the same as the injection system should be the same.
So here goes. I have checked the main wiring diagrams for my RRC and also looked over the spare injection loom I have. The white wire that is not connected could well be why your engine won't fire. The white wire is most likely on the ignition circuit and I would wager is probably the feed for the ignition amplifier.
Right or wrong let's see if we can narrow this down a bit. Look at your coil - there should be a white wire on the + terminal this is the ignition live feed. The white wire splits in the loom the other end of it goes to the ignition amplifier along with a white and black stripe wire, the amplifier wires have a moulded black plug on them that connect it to the amplifier on the side of the distributor. Unless you have a remote amplifier.
Note also there should be a capacitor attached to the coil + side. The white and black stripe wire (coil negative) also splits in the loom - this goes to pin 39 on your ECU and is the engine speed input. This wire comes out from the loom under the Air Flow Meter plug.
So that deals with the basic ignition circuit.
The alternator (there may be differences here so be careful). Main cable, big and red or brown simple enough. There should be a smaller brown and yellow stripe wire, this is the sensing wire that goes to your charge light on the dash. Then there should be a white with grey stripe wire, this will probably have an insulated spade connector, this is the RPM input for your rev counter.
Last bit, injection harness. The injectors are not fired sequntially so that makes things a bit easier. As long as you have the left and right banks the right way round there should be no problem. The injector plugs are normally a grey colour but there are two other connectors - one black and one white. The white connector is for the coolant temperature thermistor and the other is for the fuel temperature thermistor. The coolant sensor is the one at the front right hand side (when facing your engine). Basically it is on the top there behind your dizzy. The fuel one is the one on the fuel rail (unsurprisingly:doh
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So hopefully you can now check that you have all the right ignition wires and injection wires in the right place. All other things being equal I hope you can get it started.
Good Luck.