280z 1976 stalls after startup. Throttle body switch?

[NewZed]

Might be that your ignition module is going bad.  When that happens extra sparks are created which also fire the injectors more often.  Usually that will show up on your tachometer as erratic needle movement, excess RPM or a quivering/jumping inactive needle.

 

Make sure that you marked the original position of the AFM vane, in case you find that the source is somewhere else.  The AFM should never really need adjustment on a stock engine.

Edited December 29, 2020 by NewZed

[Sjoost]

NewZed,

Indeed  did mark the original location on the AFM indeed. I agree, that adjusting it leaner would prob not provide the solution to the real issue.

I have 2 spare ECU's which I also tested, making no difference. Alo, I did not see any strange RPM needle movement. I did see some strange voltage movments i now recall.

 

Therefore now I am really focusing in the Ignition coil. What is your thought on the Ignition coil being bad, and with too high resistance and not dropping back.

 

I got that info from this video: 

 

Edited December 29, 2020 by Sjoost

[NewZed]

40 minutes ago, Sjoost said:

 

Then, while engine was running, I saw some discharge sparks from the Ignition coil center to the - terminal. Figured that could also have been the spark sound I heard earlier.

 

I kind of overlooked that.  You definitely do not want to see sparks anywhere in the engine bay.  The spark jumping to the negative terminal is definitely bad, it might be a sign of bad wires, or the center wire not completely seated in the coil.  So you need to fix your wires for sure, make sure the center wire is firmly seated in the coil and the distributor.  But you also need to check the rotor and the distributor cap also.  Spend some time making sure those parts are in good shape.  Even having your spark plug gap set too wide can cause the spark to jump to where it doesn't belong.  The spark will take the easiest path to ground.

 

One side effect though of the coil discharge jumping to the negative terminal is that it can damage your ignition module, since the negative terminal is connected to the module.  Something to be aware of.  But first, get some good wires, and tune-up parts and get the system to the point where the spark only passes through the spark plug wires.  You should never see or hear sparks in the engine bay.

[Sjoost]

NewZed,

 

I agree. Arcing to negative will kill my ECU. I checked the seating of the center wire in the coil, and really doubt it was seated correctly. I moved the isolation cap a bit further down the cable, to be able to protrude the wire connecter further into the coil. I did not start the engine after that.

I do have the impression, that the arcing was due to that and could have been solved now by setting the wire in better. 

 

Still, I am doubting the condition of my coil. The resistance & Richness of fuel mixture.

From EE-34:

 

My combination is 1.3 (external resister) +1.8 (coil) = 3.1ohm which obviously is more than the 2 ohm, suggested to replace the ignition coil.

 

So I think I need a low ohm new ignition coil.

 

 

[NewZed]

I don't know how much modifying you want to do but here are a couple of links about replacing your ignition module and coil, and getting rid of the ballast resistor.  All of which will give you a stronger and more dependable spark.  These old ignition modules are dying at a regular rate after 40 + years, and the ballast resistors go bad also.

 

It's easy to do and easily reversed if you need to.  And pretty cheap.

 

One of the guys is from your area of the world.

 

https://www.classiczcars.com/articles/electrical/replacing-the-280z-tiu-with-an-hei-module-r67/

 

https://www.classiczcars.com/profile/25507-sscanf/

 

 

[Sjoost]

Wow nice links.

 

I will indeed also update the Ignition module as per the instruction. Ordered the items already.

 

I will also update my coil.

 

Thx so far.

[Sjoost]

NewZed,

 

Question,

will a HEI module also work with the stock point contacts in the distributer?

 

What startup resistance, and running resistance would it need for a coil with the HEI installed, with point distributer?

I have purchased a low resistance Flame thrower II (0.6 ohm) which firstly I was planning to replace just the current 1,8 ohm coil. This to see if my issue is solved.

If that does not give improvement, I will put in the HEI module (pertronix d2000) and replace the stock ignition module. As I understand, the external resister can then be bypassed, but will the coil not need to be with a higher resistance than 0.6ohm (I could put in my 1.8 Ohm old one)? 

 

Hope you could advise me here.

 

Thx, Joost

 

 

[NewZed]

1976 should not have points, it should have a magnetic pickup system.  The GM HEI module is designed for that type of system that's why it works well in the Nissan application.

 

The 0.6 ohm Flame Thrower should work well with the HEI module.

 

Yours might have one or two pickups but you can only use one if you convert to the HEI module.  The second pickup is for emissions purposes, it's not a big deal to swatch to one.

Edited January 8, 2021 by NewZed

[Sjoost]

Wow that gives me a lot of clarity. I did find out from the FSM that the cali model has one pickup point and the non cali, 2. Also the wiring is bit different (3 wires). 

For sure now I know that when my coil comes in, I will try that first. Then upgrade the HEI and see what that does. I will leave the distributer as it is for now.

 

Today I rechecked all the sensors on the thermostat housing, and found my thermostat itself bit worn out. Not sure if that was functioning as should, but it did open eventually when I put a heat gun on it. I will replace it anyway. I also still have a faulty temp gauge which I can't solve. I checked the gauge sender, the Temperature sensor, all with resistance values as should be expected. Measured at 5degC, 15degC, 20degC ,50 degC and 85degC. So sensors are fine. When I ground the gauge wire at the sender, the gauge also climbs up to max on the gauge in the dashboard. So I was wondering if it could be that those sensors are not getting any warmed up fluids? Still eventually all should warm up from the engine I should suspect. Coolant level was covering the sensors. Maybe the Thermostat would remain closed? Or could it be the water pump? Feels like I am running from one thing into the other, but that is probably how things need to get solved (and I get to know the car better).

 

Another thing I found and which I need to check. The fuel pressure regulator. Fuel pressure is spot on when (starter lead wire disconnected) fuel pump is running 2.5-2.6 bar. When the engine runs, it drops too much I feel (to 2 bar). Since all sparkplugs show rich mix, could it be the Fuel Regulator is faulty and fuel is sucked in to the intake manifold via the vacuum line, which brings it to all cylinders?

I will check if the vacuum line is dry. If not, I suspect the regulator as well. I was trying to find one, but they are hard to find (3way with a vacuum line). Is there any known alternative that would work?

 

Well, lots of checking to be done again.

 

Thx for your continues replies NewZed. It really help me in my quest to solving this issue 

 

[Sjoost]

Update:

Checked fuel pressure valve vacuum line for possible leak to inlet manifold. But the line was dry. No signs of petrol going through there. That one ruled out.

 

 

 

[Sjoost]

Update,

I installed a 0,6 ohm coil. Issue was still there.

I upgraded my Ignition module to a HEI (flame Thrower D2000) and jumped the ballast resister

 

Run the car today. When the car is warm starts running bad. With my fuel pressure gauge installed, I noticed the pressure dropped to 0! Somehow the pump stops running after engine is warm! If I startup again, it runs fine, but pump stops sooner as the engine is warm.

 

I also noticed, when I play with the gas peddle by moving it heavily, the rev meter jumps around and also to 0 sometime!

 

But why would the pump stop running? This could have been to problem all along but noticed it now (or I have introduced a new issue).

 

Cheers, Joost

 

[NewZed]

1976 has a switch in the AFM that controls the fuel pump relay.  When you start the engine cold the idle speed is higher and air flow keeps the switch closed.  As idle speed drops air flow does too and the switch might be closing.

 

You can check that possibility by taking the black cover off of the side of the AFM and manipulating the counterweight by hand.  Ot you can just watch the switch, it is just two very small contact points attached to a piece of stiff wire.  You can bend the wire to adjust the switch if needed.

 

Another check is to just turn up the idle RPM and see if that makes a difference to keep the pump running.

 

Here's a picture.  Don't mess with any of the things shown in the link, he's showing how to fix an AFM that has been messed with.

 

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

 

 

[Sjoost]

Well, finally good news.

 

Somehow the pump contact on the AFM was very critical. Noticed it when I has the ignition on 'on"  and closed the pump contact on the AFM. Pump would run. 

So with throttle in (and playing with the gas), the contact would regularly be lost, making the pump to stop, and making the engine run bad. Somehow (maybe due to some heat) this would occur when engine was running for some time.

And the "Start" circuit runs different (for the pump at least) and that is why it would start every time with no issue.

 

Bent the contact a bit, so it would be closed when AFM flap would open, and cleaned the contact area.

 

All in all now I have a HEI upgrade (maybe the Ignition module was also bad, who knows) with a low resistance coil. It works!

 

Thx for all your help and advise.

 

Take care,

 

Joost