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78 Z - Water Temperature Switch - Blue Wire - Help!


cherb32

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Hello,
 
I am currently restoring a 78 Z and have run into a wall with the previous owner's hack job.
 
Can anyone help me with a picture or wiring diagram for the Water Temperature Switch (not the temp sensor) on a 78 Z? The sensor has two wires, one blue (with male bullet connector) and one black for ground. I know that the blue wire connectes to the red one, but I have spent hours searching online trying to find out where that red wire comes from and the FSM isnt really helping much. I am missing this wire completely and I believe its making the Z run rough onelce its warm (runs great when cold).
Does this red wire turn into any other color further back towards the washer bottle or does it cone from somewhere else?
 
I did notice that I do have a small harness that has been cut by the previous owner. The harness runs towards the brake master cylinder reservoir and thats where it is chopped. The harness has one blue, one green/yellow wire and one black wire. All have female bullets. Is this harness related to the temp switch or is it for the A/C in whoch was also removed by the previous owner.
 
41e7e093c322669bd28be545cc47508f.jpgb84e3a253714a3a4fa172004338261ac.jpg
 
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As far as I can tell, the 78 did not use a temperature switch like that. According to the documentation, the 76 was the last year for such a device.

I wonder if you PO swapped parts around. Maybe a replacement motor? Maybe a replacement thermostat housing?

Can you pop the distributor cap off and take a pic of the guts inside the distributor?

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Sure. See attached pics.

I also took a picture of the main harness for injectors and other temp switches as well as the area where the other wires were cut.

I guess piecing these cars together isnt too far fetched these days but thank you for confirming that this year doesnt need one. I saw that it was plugged in the FSM but I was naturally second guessing.

Id like to rule out the other three wires as the harness runs to the opposite side near the battery. So I am doubting these were for the temp switch and more for the deleted A/C compressor.

But ultimately, if I dont need the switch then thats great! Thanks for the help!
657e5caa1386eaf754935c8067b352ca.jpg7b3144dbfaca9932b59e2aedbbe7be61.jpg5dfaaabf51c76b19016aa0d431213e56.jpg

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Well I'm not ready to come to any conclusions yet, but I did take another look at the documentation, and I really can't find any reference to that kind of temperature switch for 78. And for the years that DO have a device like that, it's used to change the ignition timing from "advanced" (when the engine is cold) to "retarded" (once the engine warms up).

However, you have a single pickup distributor, which does not support switching ignition timing based on temperatures. I don't know why that temperature switch is there, and what it could do for you, even if it were connected.

76 uses a device like that, and the connection from the harness out to the switch is a red wire, but swapping a 76 harness into a 78 would be a big job and have a whole bunch of pitfall issues.

What do you know about the history of the car?

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Well I'm not ready to come to any conclusions yet, but I did take another look at the documentation, and I really can't find any reference to that kind of temperature switch for 78. And for the years that DO have a device like that, it's used to change the ignition timing from "advanced" (when the engine is cold) to "retarded" (once the engine warms up).
However, you have a single pickup distributor, which does not support switching ignition timing based on temperatures. I don't know why that temperature switch is there, and what it could do for you, even if it were connected.
76 uses a device like that, and the connection from the harness out to the switch is a red wire, but swapping a 76 harness into a 78 would be a big job and have a whole bunch of pitfall issues.
What do you know about the history of the car?


Well, all that I know about the history is that the car was garaged for a bit by the first owner, the second owner (the one I purchased it from) let the car sit in a ditch in his back yard for a little over ten years after his daughter left for college. He eventually took it to a shop in Reno where he supposedly paid $8,000 to have the engine rebuilt (so he says ). I eventually saud whatever as I was more concerned about the rust at the time which was surprisingly minimal. So, after the "rebuild", he gave it to his wife who never drive it, so again it ended up sitting for another 5 years until I purchased it for $500. I bring it back to CA to find a couple of things that were tampered with and wires that were cut. It was a but hard to see at first with everything covered in sand/dust. I eventually ask him about it and he said that his kids were out there tampering with the car as it sat. I found things like missing valve cover bolts, mismatched injector screws, missing wires, A/C removed with hanging/cut wires left over etc...

Overall, the car was in decent condition but as I restore this car, I find it hard to believe that $8,000 was thrown into this. I also believe the owner and his wife were simply victims of a shady mechanic. So, sourcing parts from a junk yard and throwing it on this car while charging 8k to an unknowing older couple.....isn't too far fetched. That is about all I know regarding the vehicles history.


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14 hours ago, cherb32 said:

I know that the blue wire connectes to the red one, but I have spent hours searching online trying to find out where that red wire comes from and the FSM isnt really helping much. I am missing this wire completely and I believe its making the Z run rough onelce its warm (runs great when cold).
Does this red wire turn into any other color further back towards the washer bottle or does it cone from somewhere else?
 
I did notice that I do have a small harness that has been cut by the previous owner. The harness runs towards the brake master cylinder reservoir and thats where it is chopped. The harness has one blue, one green/yellow wire and one black wire.  
 

Not clear which wire is "missing completely".  I have a vague memory of a red wire being part of the coolant temperature sensor harness.  It has two bullet connectors in between it and the ECU.  (It's where people tap in to add a potentiometer).

The best thing to do is to work through the EFI system tests, and give the engine a complete tuneup.

Find the engine  and head numbers and it might help ID the engine.  78 has the N47 head, everything before has the N42 head.  The engine serial number will give an idea of year of manufacture.  Engine swaps are very common.  The N47 head wouldn't have come with the switch in the thermostat housing.  The N42 head would have.

Here are the links to the two books you'll need for the electrical testing and tuneup.  Do the testing at the ECU plug and measure real numbers not continuity.  Good luck.

 

 

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Nice! Thanks for the info! It just sucks chasing this gremlin. The car runs like a champ when cold but the moment it reaches operating temp, thats when the loss of power and hiccups begin. Im starting to question the heat affecting fuel lines but I will definitrly take a closer look

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1 minute ago, cherb32 said:

loss of power and hiccups begin. Im starting to question the heat affecting fuel lines but I will definitrly take a closer look. emoji1360.pngemoji1360.png

Hiccups and loss of power, backfiring, bucking....those are the typical signs of running lean.  A common problem with the old EFI systems.  Not really clear why, maybe old electronics, different fuel, maybe the system was tuned to perfection for fuel economy.  But there's a common fix for it, the potentiometer that I mentioned.  But, before that, fuel press ure is critical to correct performance.  You have to measure it, there's no easy way to tune around it.  It has to be right.

There is just a long list of small things that need to be done to get the engines running right.  People rarely resurrect one of these old cars and are happy with the way it runs.  

Here's that fix, for after you check the other stuff.  Get those engine and head numbers, just for kicks.  There is a wide range of possible combinations that you might have.

http://www.atlanticz.ca/zclub/techtips/tempsensorpot/index.html

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Ahh yes, the potentiometer. I saw that in a few threads while I was searching for a solution. Currently, I get proper psi for fuel as I installed a gauge between the furl rail and filter. I also installed an additional filter between the tank and fuel pump to catch any of the remaining rust particles from the tank. I will definitely get a potentiometer though as multple posts say that actually alleviates the issue Im having by increasing the resistance. So it will help but I'm unsure if it is a trusted long term solution. If it is then that will save me a fraction of the headache.

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15 hours ago, cherb32 said:


5dfaaabf51c76b19016aa0d431213e56.jpg

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It has the 78 fuel rail.  But many of the factory hose clamps have been replaced, so somebody has definitely had those parts off in the past.  Typical mystery motor.

You can piecemeal things, or do a thorough tuneup in one shot.  You'll probably end up doing everything by the time you're done.  

Compare mileage to valvetrain condition and you can probably see if there is $8000 in there.  There are other external clues too.

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