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

[SteveJ]

1 hour ago, NocturnalEmber said:

Another random sidenote: I replaced the green fusible links today (the ones on the harness near the battery) with ones I got from Zcardepot.  Does anyone happen to know of a better supplier for these? They lack the locking tab on the ends of the fusible links and as a result they come loose from the connectors very easily.

 

I'm really worried about these just dislodging from the connectors and breaking the connection when the car becomes roadworthy.  So if someone can recommend a place I can buy the oem green fusible links on the wiring harness near the battery that have that locking tab to hold them in the factory plugs, that would be awesome!

 

  The car has come a long way since I have gotten it, but this running issue is definitely a tough one.

OEM - https://www.nissanpartsdeal.com/parts/nissan-fusible-link~24161-28500.html

[NocturnalEmber]

20 minutes ago, SteveJ said:

OEM - https://www.nissanpartsdeal.com/parts/nissan-fusible-link~24161-28500.html

@SteveJ Hey! How are ya!  I thought you had disappeared! 

 

I looked at those online, too, and they look like they are lacking the tab cutout in the center of the bottom of the female piece that sticks up to lock them into the factory plug, Maybe its just a stock ish photo, and the ones with that part number actually do have the locking tabs on them?

 

Based on what's changed in my thread, did you have any suggestions Steve on what you would recommend I look into to get the engine running better and actually able to rev more than 20% without hitting an invisible wall? (and of course the no hot restart).

 

Much appreciated!

 

 

[SteveJ]

If you're worried about the contact, you could remove the heat shrink and stock terminals, and crimp the new terminals like these: https://www.ebay.com/itm/314175912098 on with heat shrink.

I have to admit that I haven't been following the rest of this thread much. There are too many rabbit holes.

For hot restart, look at what can be affected by heat:

1. Fuel rail. Test by parking with the hood open. If the problem goes away, then you could be boiling your fuel. I would install a fuel pressure gauge to verify. If the fuel pressure goes down (FPR leaking down), the chances of boiling the fuel goes up.
2. TIU. Test by having a can of dusting air. If the problem happens, hold the can upside down and spray the TIU. If the problem resolves, replace the TIU. This also applies to the matchbox if you have done the 280ZX distributor swap.
3. ECU. I think I saw someone suggested percussive maintenance. If the problem goes away after you rap on the ECU a couple of times, replace the ECU.

I am not sure what you mean about not being able to rev about 20%. If the car won't take load, that's usually a fuel problem. (I looked back on the thread, if the car can't maintain speed, it's likely a fuel problem.) It can be a spark problem if you have a weak spark on 1 or more cylinders. A friend couldn't figure out why his 240Z wouldn't go above 3000 RPM under load. He didn't have an obvious misfire problem, either. He's a very good Z wrench, but he was too close to the problem so he couldn't see the forest for the trees. I started working from the coil down to the plugs. Once I got to the distributor, I pulled off each plug wire, one by one. On #2, the plug wire was not fully seated into the cap, though the insulating boot was firmly over the cap. I got the wire seated against the metal, and the problem went away. Without load, the weak spark wasn't manifesting itself. However, under load, the weak spark from the extra gap caused poor combustion in #2, and the car was running on 5 cylinders. I have a short form video on Youtube at myZcarlife about that.

[NocturnalEmber]

4 hours ago, SteveJ said:

If you're worried about the contact, you could remove the heat shrink and stock terminals, and crimp the new terminals like these: https://www.ebay.com/itm/314175912098 on with heat shrink.

I have to admit that I haven't been following the rest of this thread much. There are too many rabbit holes.

For hot restart, look at what can be affected by heat:

1. Fuel rail. Test by parking with the hood open. If the problem goes away, then you could be boiling your fuel. I would install a fuel pressure gauge to verify. If the fuel pressure goes down (FPR leaking down), the chances of boiling the fuel goes up.
2. TIU. Test by having a can of dusting air. If the problem happens, hold the can upside down and spray the TIU. If the problem resolves, replace the TIU. This also applies to the matchbox if you have done the 280ZX distributor swap.
3. ECU. I think I saw someone suggested percussive maintenance. If the problem goes away after you rap on the ECU a couple of times, replace the ECU.

I am not sure what you mean about not being able to rev about 20%. If the car won't take load, that's usually a fuel problem. (I looked back on the thread, if the car can't maintain speed, it's likely a fuel problem.) It can be a spark problem if you have a weak spark on 1 or more cylinders. A friend couldn't figure out why his 240Z wouldn't go above 3000 RPM under load. He didn't have an obvious misfire problem, either. He's a very good Z wrench, but he was too close to the problem so he couldn't see the forest for the trees. I started working from the coil down to the plugs. Once I got to the distributor, I pulled off each plug wire, one by one. On #2, the plug wire was not fully seated into the cap, though the insulating boot was firmly over the cap. I got the wire seated against the metal, and the problem went away. Without load, the weak spark wasn't manifesting itself. However, under load, the weak spark from the extra gap caused poor combustion in #2, and the car was running on 5 cylinders. I have a short form video on Youtube at myZcarlife about that.

Hey Steve, thank you for continuing to provide insight, it's been critical to getting the car to where it is.

 

In regards to your suggestions:

1)I have a fuel pressure gauge and a T on order that should be here by Friday. To re test the fuel pressure. However, the way the car has been behaving, I've never actually driven it on the road, and its never ran for more than 5-7 minutes at a time inside my garage and all of those times the hood has been open.

2) The problem has been consistent I want to say since I have gotten the car to be able to start after I put in the fuel pump and lines (car didn't have a pump when I got it.) It will start (takes a few seconds of cranking if its sat for weeks), runs very rough, but will generally stay running until shut off and then will not restart when hot (will crank all day and try when hot though, and you can hear it fire but not enough to start.)

During this time I can give it throttle, and the rpms will raise a small amount, but after about applying 15-20% throttle, the revs stop increasing for the remainder of the accelerators range of motion. So after it hits what it revs to, it will not rev higher regardless of how much more you push the throttle down, though it will hold that increase until you let off.  Plugs have maybe 1/2 hour runtime and are black.

3)I will try the percussive maintenance.

All of your diagnosis and troubleshooting suggestions have helped tremendously. I now have fully working gauges, the issue of the interior warning lights intermittently working has been solved, and the brake light on the cluster and signal now works (with the exception of the left signal which stays on, but I believe that to be the signal switch itself.)  So the car has come a tremendously long way.

 

 

[SteveJ]

First, establish the baseline on your fuel pressure. Measure it at idle, and then step through the engine speed at around 500 RPM increments, noting the fuel pressure. See if it starts to tail off. If it does not, then it could be spark. 

If the plugs are black, why? Is the fuel pressure too high? Is oil getting past the oil control rings? Is the exhaust visible? Is there a lot of soot on the inside of the tail pipe? Is your spark that weak? Do you smell gas in your oil? Pull your dipstick and sniff.

Be sure to double check that the plug wires are firmly attached to the coil, distributor cap, and plugs, per my previous post.

What fuel pump did you install? What is the flow rate?

 

[NocturnalEmber]

13 hours ago, SteveJ said:

First, establish the baseline on your fuel pressure. Measure it at idle, and then step through the engine speed at around 500 RPM increments, noting the fuel pressure. See if it starts to tail off. If it does not, then it could be spark. 

If the plugs are black, why? Is the fuel pressure too high? Is oil getting past the oil control rings? Is the exhaust visible? Is there a lot of soot on the inside of the tail pipe? Is your spark that weak? Do you smell gas in your oil? Pull your dipstick and sniff.

Be sure to double check that the plug wires are firmly attached to the coil, distributor cap, and plugs, per my previous post.

What fuel pump did you install? What is the flow rate?

 

@SteveJ, I pulled up info on my fuel pump at the bottom (I've linked it) Does anything about that seem off?

Regarding the baseline on the fuel pressure and in 500 RPM increments - The only thing I will be able to measure is fuel pressure at idle, and then whatever the engine speed happens to be after I apply about 15-20% increase in throttle ( want to say the tach shows less than 1,000 with the throttle increase.)

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.

There is no visible smoke coming from the exhaust (blue, black, etc.) 

I've replaced the Cap, rotor, plugs, and wires before I started the car up, so all of those components are new. I verified that everything is snug with the ignition system to be sure.

The fuel pump I installed was I believe a Delphi pump from Rock Auto.   Here are the specs:

 

https://www.rockauto.com/en/moreinfo.php?pk=1112295&cc=1209260&pt=6256&jsn=837

Does anything seem off about those numbers to you?

Edited October 18, 2023 by NocturnalEmber

[Reptoid Overlords]

16 hours ago, NocturnalEmber said:

So after it hits what it revs to, it will not rev higher regardless of how much more you push the throttle down, though it will hold that increase until you let off.  Plugs have maybe 1/2 hour runtime and are black.

 

The fact that it will not stall out as you increase throttle strikes me as odd.  My experience with engines that are running way too rich is that at some point during the throttle range they stall due to too much fuel, but yours is staying at a constant peak RPM until full release back to idle.  If the plugs are black(sooty)then there's no denying that it's running rich i guess.  I forgot if you mentioned if you have a catalytic converter installed?  Or did your car ever have a catalytic converter?  I totally forgot when they started putting cats on the Z. 

Edited October 18, 2023 by Reptoid Overlords

[NocturnalEmber]

29 minutes ago, Reptoid Overlords said:

The fact that it will not stall out as you increase throttle strikes me as odd.  My experience with engines that are running way too rich is that at some point during the throttle range they stall due to too much fuel, but yours is staying at a constant peak RPM until full release back to idle.  If the plugs are black(sooty)then there's no denying that it's running rich i guess.  I forgot if you mentioned if you have a catalytic converter installed?  Or did your car ever have a catalytic converter?  I totally forgot when they started putting cats on the Z. 

It does not have a cat (car is a 1978 federal.) 

 

I will say that when I had let the car idle for a few minutes, touching the gas pedal could then cause it to immediately die, and THEN it will move onto the whole "cranks, will fire and try to restart, but will not restart, further cranking is an effort in futility."  After it has some time to itself, (I haven't determined how much time that is) it will start again, and the process repeats.  Giving it gas when it starts up from cold though will result in the whole situation I described in my last post.

[SteveJ]

@Reptoid Overlords is probably thinking there is a constriction somewhere, either in or out, that is limiting the engine speed. That is what I was angling for, too, but starting with fuel.

The fouled plugs indicate rich conditions unless the rings are so bad on each piston that you're getting oil into all of them. Too much fuel would overwhelm the spark, but I would expect the engine to die at that point.

What I was asking you to do in my previous post was to see if you could correlate fuel pressure to engine performance. Since you don't have the fuel pressure gauge installed, all of this can only be speculation. Data is more important. I was suggesting 500 RPM increments only because it would be easier to differentiate monitoring points. Ideally, you would make a video with a tachometer (from a timing light or multimeter) and fuel pressure gauge in the same shot, then we could correlate the engine sound, engine speed and fuel pressure. (A video done correctly can be very helpful for remote diagnostics. I knew I had an exhaust leak in my 240Z, and I sent a video slowly moving across the engine while the car idling to a friend. He said the leak was around #2, and he was right.)

So could there be a restriction in the intake? That is worth examining. Is the flap moving cleanly and easily, or is it getting hung? Is there something in the airbox or between the airbox and AFM (think critter houses) that could be blocking air flow?

Could the exhaust be blocked? Again, I would expect the engine to choke and die, but I could be wrong. I have seen several videos online of mechanics shaking a squirrel's stash out of a muffler.

Lastly, as I said before, make sure all of the wires on the coil, distributor cap, and plugs are fully seated on the components, especially the coil to cap wire. A weak spark could account for poor performance. 

Since this thread is already 13 pages, would you please state again the age of the coil, cap, rotor, and wires? Are you on the stock ignition, or do you have a ZX distributor or other ignition?

[Zed Head]

8 hours ago, 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.

Sounds like your AFM is not connected, electrically.  Might be that the connector/plug fell off of the bottom.  It happens.  You can can check via the pins at the ECU connector to be sure.

[SteveJ]

12 minutes ago, Zed Head said:

Sounds like your AFM is not connected, electrically.  Might be that the connector/plug fell off of the bottom.  It happens.  You can can check via the pins at the ECU connector to be sure.

That sounds like a good avenue to pursue.

[NocturnalEmber]

19 hours ago, Zed Head said:

Sounds like your AFM is not connected, electrically.  Might be that the connector/plug fell off of the bottom.  It happens.  You can can check via the pins at the ECU connector to be sure.

 

That was one of the first things I've checked to be honest, On the Z its somewhat difficult to get at, but its just a clip thats under it that locks in place with that little bend of metal that wraps around 3/4 sides, right? 

 

19 hours ago, SteveJ said:

That sounds like a good avenue to pursue.

At this point I'll pull the AFM out and ensure the connector is seated, I swear I felt back there, but I could very well have felt wrong. I'll get out there and verify the connection and report back today.

23 hours ago, SteveJ said:

 

Since this thread is already 13 pages, would you please state again the age of the coil, cap, rotor, and wires? Are you on the stock ignition, or do you have a ZX distributor or other ignition?

Sure thing @SteveJ

 

Coil - New (NGK)

Cap - New (Standard)

Rotor - New (Standard)

Wires -New (NGK)

Plugs - New (NGK Platinums) Very much fouled now.

Regarding the ignition it is completely stock to my knowledge, I don't believe there is anything different from the factory distributor.