wimberosa
SILVER Star
- Thread starter
- #141
For posterity....a bit of data in case anyone has the 78+ with yazaki wire and needs to remove it...or understand what it is. I had removed mine when I was working on my main wiring harness because I did not imagine a big pink wire in the middle of my harness was oem (it is oem). The following is just data that I considered on how to get my truck back within design parameters now that its missing this yazaki wire.
A bit of background...
Early coils used an external resistor (ballast resistor) usually made of a wire coil encased in ceramic. It usually sat in the engine bay near the coil which it is meant to protect. Its operation is to reduce the normal operating voltage supplied to the coil to somewhere in the 6 to 9v range. The resistor is usually bypassed to supply the full 12v...generating a hotter spark through the coil during starting of the engine. Around 1978 toyota removed the external ballast resistor and instead went with a heavier gauge resistive wire embedded in the harness (the yazaki wire). For the 1979 the emissions control module took over the function of bypassing the resistive wire and supplying the full 12v to the coil during start. (See figure below)
Later models such as the fj60 completely removed these wire/ballast resistors and instead just have a coil that is designed to handle the full 12v load. Its been stated that even a coil meant to be used with a wire/ballast resistor can still function if the resistor is missing and the full 12v is continuously supplied. Clearly that is true but those coils were not designed for a continuous 12v and thus running it like that is outside the design parameters...and thus could perhaps prematurely fail. I suspect the opposite can be true as well...in that you could run a coil that does not need a ballast resistor with a ballast resistor. Again...that is outside the design parameter of those coils and may perform sub optimally.
For me I now had two options....given no yazaki wire and didn't want to put it back. Option one for me was to run a later coil (part number 90919-02113) which is designed to be used without a wire/ballast resistor. I ALSO now have the option of running a fj60 dizzy+igniter+coil in the normal manner of supplying continuous 12v.
If you choose to remove the yazaki wire, it is in the main harness and both its beginning and end point are roughly in the same spot in the harness. Its basically just a big loop of wire. You can directly remove the yazaki wire and connect the wire it was connected to at its end, back to the the wire where the yazaki connects at its start. Here is an illustration of what I'm talking about and where it sits in the harness.
Here is the 1979 diagram with and without the yazaki and how the bypass wire works through the ECM
A bit of background...
Early coils used an external resistor (ballast resistor) usually made of a wire coil encased in ceramic. It usually sat in the engine bay near the coil which it is meant to protect. Its operation is to reduce the normal operating voltage supplied to the coil to somewhere in the 6 to 9v range. The resistor is usually bypassed to supply the full 12v...generating a hotter spark through the coil during starting of the engine. Around 1978 toyota removed the external ballast resistor and instead went with a heavier gauge resistive wire embedded in the harness (the yazaki wire). For the 1979 the emissions control module took over the function of bypassing the resistive wire and supplying the full 12v to the coil during start. (See figure below)
Later models such as the fj60 completely removed these wire/ballast resistors and instead just have a coil that is designed to handle the full 12v load. Its been stated that even a coil meant to be used with a wire/ballast resistor can still function if the resistor is missing and the full 12v is continuously supplied. Clearly that is true but those coils were not designed for a continuous 12v and thus running it like that is outside the design parameters...and thus could perhaps prematurely fail. I suspect the opposite can be true as well...in that you could run a coil that does not need a ballast resistor with a ballast resistor. Again...that is outside the design parameter of those coils and may perform sub optimally.
For me I now had two options....given no yazaki wire and didn't want to put it back. Option one for me was to run a later coil (part number 90919-02113) which is designed to be used without a wire/ballast resistor. I ALSO now have the option of running a fj60 dizzy+igniter+coil in the normal manner of supplying continuous 12v.
If you choose to remove the yazaki wire, it is in the main harness and both its beginning and end point are roughly in the same spot in the harness. Its basically just a big loop of wire. You can directly remove the yazaki wire and connect the wire it was connected to at its end, back to the the wire where the yazaki connects at its start. Here is an illustration of what I'm talking about and where it sits in the harness.
Here is the 1979 diagram with and without the yazaki and how the bypass wire works through the ECM
Starting to build some confidence she'll hang together.
