Super rich plugs fouled

[Dave WM]

I have not tried putting it back in to see if messing with it may have fixed it. I have been focused on the AC, seems like It must be the check valve, I have 16-17 on one side and nothing on the other, so the vacuum bottle never gets pulled down. For now I just stuck a piece of tubing to join the two "S" lines together so my AC idle up and ducting servos all work again. I would like to try disconnecting the return line and feeding it into a gas container just to see if my theory of a stuffy return line could be influencing the fuel pressure. I am liking the idea of just popping for the OE pump that uses a built in regulator that limits the output to 45 psi (think that is what I read).

[Captain Obvious]

Dave, Focus my friend... Focus!    

[Dave WM]

I am all over the place today 

[Captain Obvious]

Haha! Thanks for the laugh!

Pull the connector off the ECU and take some measurements. I'd start there. Well actually I'd start by wiggling the WTS, and AFM connectors...

And for checking the sensor resistance measurements, I just posted a chart that should help:
http://www.classiczcars.com/forums/topic/56146-280z-efi-temperature-sensor-vs-resistance-chart/

 

Edited September 9, 2016 by Captain Obvious
Added chart link

[Zed Head]

6 hours ago, Dave WM said:

Decide to cut to the chase, swap in a spare ECU, starts right up. runs fine. So the plan is to open the old one up and look for any obvious looking failed parts. I sure am glad I had that spare ECU...

Brass tacks and all that (whatever that means, I've never really known).  Dave had a problem, he swapped ECU's and the problem went away.  In the interest of avoiding distraction and unnecessary excursions maybe re-installing the "bad" ECU would be worthwhile.  If the problem follows the ECU, it's the ECU.  Right?  Just saying...

[Dave WM]

ZH that's the plan for tomorrow put the old one back together after mussing with it, other than the small carbonized looking junk I cleared off the one trace, no other action taken on it. I did try going back to it when I did the 1st swap, and the problem returned so I know it was ECU related. The only question now is did the action taken have any effect. I am REAL glad I had the extra ECU, typically that is the last place I would go to, and it prob would have driven me nearly mad checking all the usual suspects.

Edited September 9, 2016 by Dave WM

[Dave WM]

started car cold with replacement ECU, started right up ran fine.

replaced ECU with the one that was a problem yesterday (still cold car), started right up ran fine.

Left the replacement in, will drive car later and get up to full temp, then try the swap again.

Anybody know what the two white wires that come out of the wire harness right at the 35 pin connector (they have bullet connectors) is for? I looked at the FSM and saw something that maybe it, control and checking term? two white wires that appear to go to the ECU pins 11 and 26. Nothing about them that I could find. 

update on 11 and 26 Search and found Capt O had mentioned injector signal test points on an earlier thread.

Edited September 9, 2016 by Dave WM

[Captain Obvious]

Pins 11 and 26 internally connect to the open collector outputs of the two output transistors through 1.5K resistors. So you could put a scope on those two pins while the ECU is running instead of probing the injector connections directly. I believe them to be test connection outputs to check the operation of the ECU.

You could also wire those pins to +12 and disconnect all the injectors and view the output signal as a clean square wave without any noise from the injector impedance. In other words... Instead of pulling the transistors up to +12 through the injectors, you can disconnect all the injectors and pull the transistor collectors to +12 through that 1.5K limiting resistor. Then you could scope the injector pins to see a clean square wave drive signal. Good for bench testing and may have been used for Datsun's ECU tester modules.

About the white wires though. Interesting because I don't have any white wires with bullet connectors. In fact, my harness doesn't even have pins 11 and 26 populated.  The ECU has pins there, but the corresponding harness positions are empty. I wonder if they put those white wires on the earlier 280's and then decided that things were reliable enough that they didn't need them anymore on the later years.

[Dave WM]

I will confirm the wires I have are indeed connected to the 11/26 pins on the 35 pin connector (just a continuity check from the bullets back to the connector) the wires exit from the connector right above where the wire harness goes into the socket, just hang there covered by the kick panel. Going to get some new plugs as well so I can do a check of the fuel mixture, I cleaned the old ones up, but not well enough to evaluate the air/fuel mix since they stained so dark now.

[Captain Obvious]

I found my notes and here's what the output stage looks like:

Note that I didn't have a Darlington symbol handy that included built in base resistors (and I didn't feel like creating one), so I left those two built-in resistors out. I can tell you, however, that the total resistance of the two of them is 2.7K Ohms total.

 

[Dave WM]

Put some new plugs in it, seems fine now with the replacement ECU. Will try the old one later. Still wondering about the fuel pressure, the plan now is to get some fuel line, enough to take the return line and feed it safely into a gas container. That would eliminate any "stuffiness" on the return side. See if that effects the fuel pressure. I will prob still end up popping for the OE pump just to take the strain off the rest of the fuel system.

[Zed Head]

I wonder if you have the wiggly connector issue.  There's a fair record of sporadically bad ECU's out there.  I'll see if I can dig some threads up.

Here's one.  The guy hasn't been around for a while.  http://www.classiczcars.com/forums/topic/34229-280zzx-ecm-tech/

Some wiggle the connector comments - http://www.zdriver.com/forums/280zx-s130-forums-77/resoldering-ecu-31290/

Of course, all of these people and me included could just have been doing random things and the act of taking the ECU apart and putting it back together was what "fixed" the problem.

 

 

Edited September 9, 2016 by Zed Head