79 280zx: 3 wires going into the EFI relay

[JSM]

Ok as some of you know I'm trying to steal the 79 EFI to run on my 71. I've been staring at schematics for awhile, looking through the FSM Engine electrics and EFI sections of the FSM, but I can not figure out what the yellow wire from the body plug leading into the EFI relay does. The black and white and green wire are switched power. Assuming to run to the ECU and one to the Dropping resistors. 

I checked voltage to the yellow wire while the car is running and nothing. And nothing during cranking only and it's not going to ground.  So I let it run and cut it while the car was running.  No change. Turned the car off and back on no issues. 

The other thing I noticed, is the ECU has a large blue wire connected via a spade connector that also has switched power.  This outside of the large ECU plug.  What I noticed also pin 27 is a blue wire coming from the EFI relay (per page EF-22). So based on my testing the ECU has two sources of power coming to it, 1 from the spade and 1 from the EFI relay. 

What I would love to find is the sections that describe what the heck the body plugs do!! 

Here is a pic of the wire I cut going into the EFI relay. 

[SteveJ]

I am not a fuel injection expert, nor do I play one on TV.

If you haven't already, download the 79 wiring diagram from here: http://atlanticz.ca/zclub/techtips/electrical.htm

It appears that the yellow wire is connected to the blue wire when both coils are energized at Fuel Pump Relay (2). The yellow wire goes down to the connector that you hacked the yellow wire off and comes out as a green wire. That green wire goes into pin 26 on the ECU. It also goes out to the cold start valve and thermotine switch.

From there, you need to consult the EF section of the 79 FSM.

[JSM]

Than you very much. I did have it downloaded. I saw it go to pin 26" and then Got lost in the schematic. 

[Martzedcars]

And... may i ad... never just cut a wire that way, if you had studied that plug for a moment you could have simply taken out that single pin and later on put it back.. now you have a damaged wiring loom...

[Zed Head]

You can stick a piece of tape or plastic over the male part of the pin also to break contact.

[JSM]

10 hours ago, Martzedcars said:

And... may i ad... never just cut a wire that way, if you had studied that plug for a moment you could have simply taken out that single pin and later on put it back.. now you have a damaged wiring loom...

It's the body loom, which I don't care about.  I have no title to the car and it will be cut into pieces for scrap anyway.

[JSM]

45 minutes ago, Zed Head said:

You can stick a piece of tape or plastic over the male part of the pin also to break contact.

Good point.  One way or another Mr Yellow wire was coming out though!

[JSM]

On 1/28/2017 at 8:24 PM, SteveJ said:

I am not a fuel injection expert, nor do I play one on TV.

If you haven't already, download the 79 wiring diagram from here: http://atlanticz.ca/zclub/techtips/electrical.htm

It appears that the yellow wire is connected to the blue wire when both coils are energized at Fuel Pump Relay (2). The yellow wire goes down to the connector that you hacked the yellow wire off and comes out as a green wire. That green wire goes into pin 26 on the ECU. It also goes out to the cold start valve and thermotine switch.

From there, you need to consult the EF section of the 79 FSM.

 

Steve could you help me trace Pin 18. I swear i'm going blind!  I know it is switched power and I think it says it's going to coil.  It's the blue spade connector pigtail attached to the ECU plug.  I think i need to swing by FedEx office and get this thing printed out.

Edited January 30, 2017 by JSM

[JSM]

I know per the FSM it says "ignition coil trigger", but the odd thing is unplugged I still have power to both the coil and the match box of the distributor.  Car will only run plugged in though?  

[JSM]

What I'm stumped on is why does the FSM say it comes to the coil? The E12-80 distributor can run totally stand alone otherwise people wouldn't use it in the 240z. I ran continuity from the - side of the coil and got nothing. That spade goes to one pin I which believe is 18 and none other. Plus why would positive be needed for the negative side of the coil. I must not be reading something right.

Edited January 31, 2017 by JSM

[SteveJ]

Pin 18 goes to the negative on the coil and ignition module. It also branches off to a resistor to provide a signal for the tachometer. I don't have the time to dig through all of the FSM, but it is probably a trigger for the ECU to indicate engine speed.

[JSM]

19 hours ago, SteveJ said:

Pin 18 goes to the negative on the coil and ignition module. It also branches off to a resistor to provide a signal for the tachometer. I don't have the time to dig through all of the FSM, but it is probably a trigger for the ECU to indicate engine speed.

Thank you Steve. I am a dumbass. It was staring at me the whole time. I was counting the pins with the plug upside down! Not to mention the PO had positive and negative wires flipped on the coil which further compounded issues.  I got it to run unhooked from the car!