1978 280Z - Won't restart when hot, all interior gauges, fan motor, backlighting not working

[Zed Head]

On 10/17/2023 at 11:46 PM, NocturnalEmber said:

The car won't rev more than a few hundred RPMs regardless of how much throttle I give it. I can give it 10% - 100% throttle, and the engine speed will only increase by (and hold at) a small amount until I let off the throttle.

A video with good sound might help.  When you press the gas pedal are you sure that throttle blade is actually opening?  Are you working the throttle by hand with the hood open or just sitting inside pressing the pedal?

If it was mine I'd have the black cover off of the AFM and be working the throttle by hand, to be sure that things were doing what they are supposed to do.  Move the throttle blade, listen, watch the AFM vane counterweight.

I would also check ignition timing.  Retarded ignition timing can make an engine run like crap.

Your AFM numbers don't look bad.  I don't think that's the problem.  I've had a few with numbers that were off and have a theory that it's the ratio that matters.  Not sure, but 180/100 = 1.8.  205/114 = 1.79.

 

[NocturnalEmber]

12 minutes ago, Zed Head said:

A video with good sound might help.  When you press the gas pedal are you sure that throttle blade is actually opening?  Are you working the throttle by hand with the hood open or just sitting inside pressing the pedal?

If it was mine I'd have the black cover off of the AFM and be working the throttle by hand, to be sure that things were doing what they are supposed to do.  Move the throttle blade, listen, watch the AFM vane counterweight.

I would also check ignition timing.  Retarded ignition timing can make an engine run like crap.

Your AFM numbers don't look bad.  I don't think that's the problem.  I've had a few with numbers that were off and have a theory that it's the ratio that matters.  Not sure, but 180/100 = 1.8.  205/114 = 1.79.

 

 

I'm fairly certain the throttle is opening. I've manually actuated the linkage by hand more often than I've used the gas pedal, and that muscle feel I get through pushing on the linkage directly feels like its opening (difficult feeling to describe, but if you've ever manually operated a throttle linkage you know the feeling and resistance you get when the throttle plate opens and closes.)

The black cover of the AFM actually fell off a few times while the engine was running, and I can see the internals moving as the engine would take in more air. I suppose I'll move onto the ignition timing next. I don't' remember the distributor having uneven gap on the left or right of the securing bolt (it looked even I want to say.) but I'll get into it tomorrow and give it a good look through.

Edited October 24, 2023 by NocturnalEmber

[siteunseen]

20 hours ago, Yarb said:

Hey Cliff there’s a red tag on the thermotime/temp sub harness. I believe it signifies between the two sensors so you don’t get them backwards. My harness is out and not going to be used any longer so I can’t reference it on the car. Any clues from the Librarian?

I'm sorry but I just read this. Seems like the coolant wires were different colors than the thermotime wires?

I'm away from my cars at the moment but you might could figure it out by looking at these pics on Blue's Tech Tips

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

 

[Zed Head]

Could be a mouse house in the air inlet system.  It happens.  No air = no rev.

[NocturnalEmber]

2 minutes ago, Zed Head said:

Could be a mouse house in the air inlet system.  It happens.  No air = no rev.

 

I actually pulled the hose connecting the AFM to the box completely off to open up the airflow, unfortunately it didn't change the problem either.

 

 

I thought I checked the coolant temp sensor and thermotime switch bullet connectors when I installed the new coolant temp sensor, but I'll double check again to make sure they aren't connected wrong.

 

1 hour ago, siteunseen said:

I'm sorry but I just read this. Seems like the coolant wires were different colors than the thermotime wires?

I'm away from my cars at the moment but you might could figure it out by looking at these pics on Blue's Tech Tips

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

 

 

[Zed Head]

So the basic problem at this time is that the engine does not increase RPM when the throttle is opened.  Correct?

Have you checked ignition timing?  I had an car long ago with timing so retarded the engine would barely respond to throttle.  Didn't know what I was doing. I had just learned the time-it-by-ear method, and found that it didn't really work well.  Got things all screwed up.  It was a carb'ed engine.

You might also check your throttle position sensor.  I don't know what happens if it gets stuck in the idle position.  Maybe it doesn't use the AFM until it's off-idle.  It's another at-the-ECU-connector test.  In the book.

[NocturnalEmber]

12 hours ago, Zed Head said:

So the basic problem at this time is that the engine does not increase RPM when the throttle is opened.  Correct?

Have you checked ignition timing?  I had an car long ago with timing so retarded the engine would barely respond to throttle.  Didn't know what I was doing. I had just learned the time-it-by-ear method, and found that it didn't really work well.  Got things all screwed up.  It was a carb'ed engine.

You might also check your throttle position sensor.  I don't know what happens if it gets stuck in the idle position.  Maybe it doesn't use the AFM until it's off-idle.  It's another at-the-ECU-connector test.  In the book.

I haven't checked the ignition timing yet, waiting on a timing light to arrive, but thats my next stop.  In the meantime, I did confirm that the thermotime and coolant temp sensors appear to be correctly connected.

 

I also took a picture of my distributor; The old cap had slightly different positioning than the new cap I put on, but I assume this is the right positioning for the plug wires.

 

[Yarb]

The cap should be identical to your original that was removed IMO.

[Mark Maras]

@NocturnalEmber What was different when you said "slightly different positioning"?

[NocturnalEmber]

5 hours ago, Yarb said:

The cap should be identical to your original that was removed IMO.

 

2 hours ago, Mark Maras said:

@NocturnalEmber What was different when you said "slightly different positioning"?

 

I swear when I installed the new cap, the cylinder position seemed different, but I'll double check in a few minutes and get a picture for everyone. At the time, I hadn't worked on a distributor driven car in forever, plus its an NGK cap, so I figured it wasn't anything to be worried about, but now that I'm essentially trying everything in the book so far and still have this issue, I'm starting to be overly cautious.

Edited October 25, 2023 by NocturnalEmber

[Yarb]

Ryan, this could be the main culprit of your initial issues. Not to say this will be the total answer with other issues you described. When I read the post a light bulb went off immediately.

[NocturnalEmber]

I took some photos of the old cap (left) and the new NGK cap on the right.  I did my best to align them with where the retaining clips would latch onto the cap from the lower part of the distributor itself.  It looks to me like they are in slightly different positions, but this could just be me, or if they are, then maybe it doesn't matter?   I also included a picture of the wheel/reluctor and pickup, as well as the new and old rotor (new on right).