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

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

Nice write up Chickenwing, On another note, I did not have the same issue, but my wind shield blowers were not working from the leavers. Only then I found out that with an AC system on a 280z 1976 model, the flaps all work with engine vacuum. Cheers, Joost

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.

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

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

Great SteveB, Thx for reporting back. I remember the feeling, when finally the needle of oilpresser showed a good reading after trying so many senders. I still have a water temperature sender which is not showing anything on my gauge. gauge is file. also here, i have tried few senders already.... Take care. Joost

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.

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, 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:

Today's followup, Issue was, that somehow my pump would stop running after START (and a very rich fuel mixture). I checked the ignition relays. I wanted to check that after START (so in ON position), the relay was working to supply power to the AFM and Pump. I also checked the fuses in that line. All fine. I screwed back in, the Idle/flap bypass screw on the AFM. So it would force more flow through the main flap. BAM! the pump would not die anymore from START to ON. Apparently the bypass was too big, not closing the pump switch in the AFM (which only happens when the flap is forced a bit open by airflow to the engine). So that is fixed now. However, that still did not fix my suspected RICH running issue and engine stall after running for a bit (its still around 4-6 degC here, and humid). I found 2 alternative ECU's, because I wanted to rule out any issue with those. No change, car still running rich and stalling after while. So finally, I adjusted the AFM flap resistance (obviously marking it's original points). I tightened the flap, so less opening at airflow, making the mixture less rich (as I understood from my research). Started like a charm, and the engine kept running for a nice time. However, after maybe 10 minutes, and some runway driving, I was feeling misfire, and bit rough idle again. I also thought I heard a electrical discharge /spark sound... Exhaust fumes, still smelling rich. And again, it would stall (however this was definitely longer than before). After bit of cooling, engine would run again, but not for long, and only bit rough. 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. Reading online, and also the Ignition troubleshooting guide, I discovered that the thing I had not checked was the functionality Ignition coil in relating to fuel mixture. As I have now understood, if the ignition coil is bad, this can cause (among others): 1. rich fuel mixture 2. wobbly engine, especially at low rev's and hard accelerations The Ignition coil influences the frequency of injection (engine RPM). Also, once the coil could warmup, making things worse. Cooling down would improve the functionality. So I tested the Ballast Resister at the coil. 1.3 Ohm I tested the Coil alone: 1.8 Ohm What I have seen online that 1.8 Ohm for the ignition coil would be too high (should be around 0.6 Ohm primary winding, and 8.5-12.5 kOhm secondary (I get 13.7kOhm)). It would lead to rich mixture, and misfire I understand. Is my assumption correct? I am on the lookout for a <=0.6 Ohm ignition coil, but before I buy it, some feedback would help me. Cheers,

hhm did some study of FMS and injection manual, Could also be the pump contacts on AFM or, the throttle switch idle contact not being closed. In both cases, pump will stop running in the "ON' position (safety measures when engine stalls due to crash, fuel pump should stop also). Well I have some work to do this Christmas. Corona helps keeping you working on your Datsun! Merry Xmas Z lovers.

Hi ETI2K, Thank for your thoughts. I did operate the AFM flap, and would indeed get changes in the engine sounds. But eventually I ruled out the AFM as I was of the assumption that my issue was the engine running too rich and stalling. All the EFI sensors seem to work in a way that you can easily adjust it to make it richer, but making it run leaner seems to bit harder. Anyway, I think I did make good progress today. I was changing out some other things so I did not actually run the engine when testing the fuel pressure. After I finalized all those works, today I cranked it and had it running again. Starts right up, with nice 2,5-2,6 bar fuel pressure when I turn the starter to ignition (start). Somehow my starter switch has always functioned very bad, and i really need to put pressure on the key to get the pump running at ignition/start. Well after the ignition, the key turn to ON, and in the past all was fine. But now I noticed fuel pressure completely dropped to 0!. So I now thing there is a issue with my ignition switch (I did already try another ignition relay so feel that is not the issue). All that time, the issue was not that it stalled due to richness, but more to the fact that the fuel supply is cut out... I have had issued before with this ignition switch but thought I fixed them. So now first I need to get the fuel supply to remain running after start. Or is there another system that could cut out the fuel supply at start? Cheers, Joost

SteveB, Sorry for the confusion. I have an early 280z, which has the one wire setup. But the operation to the gauge is still the same, I expect. Resistance should be 1/8" below 0 psi - infinite ohms (open circuit). 0psi - 90ohms 60psi - 25 ohms 90psi - 12 ohms For the two wire version, I am not sure, but if you know the switch setting needed, and the sender gives the correct ohm's, it should work.

Hi all, Just update. Installed fuel pressure gauge today, and I had a nice 2.5-2.6 bar. So I am ruling fuel pressure out for now. I managed to find 1,5 ecu's which I hope to get in soon. I will try those. Today I cleaned the sparkplugs also. All were dry, but black. I think that is the sign for too rich (but correct me if I am wrong). From the fact that they were all dark, in similar shape, I would also rule out one of the injectores not closing (as the richness would not be to all 6). And I have already inspected and tested the cold start injector. Noting found there. I noticed my AFM adjustment screw was all the way in (turned right, clockwise). I think that means less air passes. Therefore I turned it out (counterclock) completely. Hope these measures will help, but any suggestion is welcome. Take care!