Hi all,
I need some help on working out which wire runs where. The problem started as I noticed the car started to run a bit rough and eventually started to stall and on inspection under the bonnet I noticed the engine harness smoking from the twelve pin connector right next to the diagnosis box. I cut and peeled back the loom a bit and found two black wires with a green trace, one of which was almost totally bare.
It seems I have a dead short but I would like to know where these wires run to and from so I can fit a new wire in its place. I have looked at many wiring diagrams but find them hard to understand and I am hoping one of you experts can help me out.
My fd has been off the the road for two weeks now and I am getting serious cold turkey and its such an annoying problem which nobody wants to work on for me under a million quid. I am new to the club and can\'t even put pictures up of my rex as the front bumper is off for better inspection and looks like a stock car.
Please help me restore my faith in these beautiful beasts before I decide to break it for parts! heres to hoping - crossed wired Nick:driving
what year is your car?
Hi there
The year is 1992J import
Thanks
Do you think the problem is somewhere else in the loom, or can you see where the problem is to bridge it out?
I have bridged out a whole section of loom once on an older FB - that was stone damaged under the radiator - shorted the lot out.
Unfortunately I\'ve no diagram for an FD and precious little knowledge of them. Worth checking under rad?
Also one wire smoking in a loom will take others with it unless it\'s just at the end. Sorry for that.
Hi
Any photos of the:
Engine bay location
Connector (above, end on)
Damaged and non damaged wires (colours)
Item the connector is plugged into?
Closeups to help people narrow it down.
Thanks everyone,
I will put up some pics of the problem tomorrow to show more detail as there are so many wires. - Nick
Quote from: Evil TwinHi
Any photos of the:
Engine bay location
Connector (above, end on)
Damaged and non damaged wires (colours)
Item the connector is plugged into?
Closeups to help people narrow it down.
Hi here are some pictures of my engine bay and of the actual connector where the wire was smoking. I think i have been lucky because all other wires in the loom seem to be fairly undamaged. I have cut one of the wires which was heating the most to see if the car still started but it just turns over and wont fire up. The wire goes into the connector at the bottom right and looks orange in the pics because its bare.
There are two black wires with a light green trace in that connector and both seem to have heated up (one worse than the other). As I have cut the wire and it will not start I wondered if it is fuel related.
I think I am going round in circles and need some advice on what to do next. I cant belive a couple of wires are keeping my rex off the road as I was more worried about the engine when i bought it lol.
I have also posted a couple of pics of my fd minus the front bumper!
Hi
I\'ve had a quick look. Unfortunately your photos are blurry so it\'s quite hard to see the damage.
However working with the wiring manual for 1994 from here.
http://www.rotaryart.uk.com/acatalog/1994WiringDiagramLHD.pdf
It looks to me that the connector in the photos is common connector number X12 as shown on page Z121.
According to the manual the wire you cut would have been light green/ black. This wire connects between the leading coil pack and igniter unit (on the passenger side of the engine bay) as seen on page Z28.
The other cable black/ light green cable is the shield to protect the wiring from engine electrical noise and connects back to the ECU this can be seen on page Z32.
Now I would hazard a guess from your description and say there might be a fault with the leading coil pack which caused high current to flow in the circuit. The light green/ black cable being the lightest gauge in the circuit has heated up and damaged its insulation. This has then shorted down to shield and the black/ light green wire back to the ECU. Unfortunately the ignition system is supplied by a 40A fuse, so this wouldn\'t have blown in a rush either.
I would start at the coil pack and check the primary resistance. From there I would try to make a temporary repair between the coil/ Igniter unit as per page Z28. Then see if I could get her to fire up. Hopefully the ECU will have survived the ordeal.
Plus just thinking might be worth checking the plug in case they\'ve fouled with fuel.
Anyone else got a point of view? Am I speaking rubbish? Who knows!
Hope this noise helps.
No, I don\'t think you are not speaking rubbish. A coil fault might be enough to damage one or two wires without burning out the lot. I would expect the shield wire to have taken the form of a screened cable, like a thin co-ax. Bulldog, does the burnt wiring look like it might have been screened, can\'t tell from photo\'s. Meanwhile I would does as evil twin says and trace back to the coils and see if one\'s gone faulty. If so a temporary repair would prove things.
It\'s only a hope, nothing certain here.
Quote from: David NockNo, I don\'t think you are not speaking rubbish. A coil fault might be enough to damage one or two wires without burning out the lot. I would expect the shield wire to have taken the form of a screened cable, like a thin co-ax. Bulldog, does the burnt wiring look like it might have been screened, can\'t tell from photo\'s. Meanwhile I would does as evil twin says and trace back to the coils and see if one\'s gone faulty. If so a temporary repair would prove things.
It\'s only a hope, nothing certain here.
Thanks David and evil twin, your information is being given to an auto electrician who will only look at it once I can tell him the route of the wires to take out the time consuming investigating (I dont think he is very keen to say the least). The second wire which heated up is not green/black but is black/green the same as the other but it does go into a smaller grey loom with a load of green/black wires both sides of the connector.
Also David what do you mean by a wire being screened?
Once I get to the bottom of this i will owe you both a pint!!!:guinness
As said:
The other cable black/ light green cable is the shield to protect the wiring from engine electrical noise and connects back to the ECU this can be seen on page Z32.
The black/ light green is a effectively a ground cable to shield/ screen the internal wires against electrical noise. This will normally take form as some kind of overbraid under a plastic sheath (like a coaxial (TV Aerial cable) as David said).
The grey wires you describe are also shown on connector X12 on page Z28. They help form part of the shielding system.
If you look at page Z29 it shows the routing of the cables over to the leading coil pack. It even shows where connector B1-14 hides. The connector between the coil pack ignition loom and engine loom. This might be a good place to make a temporary repair to/ from.
Hope this makes it clearer :)
Evil Twin has done all the work here, somehow I got a triple negative into the words on my post - how did that not not happen?
Bulldog, important you get the parts of the wiring diagram dowloaded into print form for your auto electrician - it makes everything a lot clearer.
I do think Evil Twin is on the right track with his research and hopefully a test of the coils will show that one has shorted turns inside it.
Also, whether it\'s peculiar to Mazda or not, I don\'t know, but the diagrams also give the run of the wiring looms and spell out where the connectors are on the car. Page Z27 is a good one.
Hi
If you look at page Z29 it gives the routing and connections for the wiring diagram on page Z28. Which is the relevant to the repair work RX7Bulldog wants to carry out.
Page Z27 shows all the routing and connections for an Automatic Starting/ Charging system.
Quote from: Evil TwinHi
If you look at page Z29 it gives the routing and connections for the wiring diagram on page Z28. Which is the relevant to the repair work RX7Bulldog wants to carry out.
Page Z27 shows all the routing and connections for an Automatic Starting/ Charging system.
OK, thanks for that. Excellent work Matey.
Thanks again guys I\'m downloading the diagrams you have pointed out, handing them to the auto electrician tomorrow along with your opinion on what is at fault. With any luck i could be back on the road soon if it isn\'t a really hard fix. I\'m starting to feel hopeful about the car again and just pray its nothing more sinister, if it is I will be back to pick your brains again. Cheers Nick