Would you believe the connection pin for the coolant sensor (for the gauge) pulled out!?    

I had to replace the bullet connector and thus the whole wire, and while I was pulling out the slack, the thing suddenly got loose, so I kept pulling and there was the end!  FYI, the pin has a wire that goes through the sensor body, to the base of the sensor, where there's a little washer-like thing that probably generates the resistance for he gauge.  The sensor is hollow.   It's not leaking coolant.

BTW-  can you get the connector for the other (EFI) coolant sensor?  It looks like a fuel injector connector, but the groove is offset, probably so you don't plug it onto the wrong thing.  The wires broke off inside the old factory connector.

I'm sure replacing those connectors didn't kill your ECU. Probably something simple like you mixed up the thermotime connector and the WTS connector somehow. If you do that, it'll run pig rich, burn you eyes, and foul your plugs in short order.

Oh, and forgot... Since the last time this topic was active:

I filed the offset tab off the AIRTEX / WELLS5S1523 (SU4115) sensor and installed it. It works great.

The plugs look fine, as I recently checked, cleaned and gapped them for the summer.  The mix should be right.  Plus I switched them just in case, with no improvement.  The only thing I didn't do  is to check the sensors directly, because they are fairly new. The only symptom I couldn't explain is a bit of a misfire, and the spark timing is at 30 degrees even before vacuum advance.  something  must've jumped?

I think I have located a local shop that knows about  L-Jet.

Edited June 4, 20186 yr by TomoHawk

I'll have to  trace  those wires. 

Did I mention the timing is 50 before without the vacuum?

Edited June 4, 20186 yr by TomoHawk

There's nothing that will jump, but it could be that your damper slipped.  That would move the timing mark.  Easy to check with the valve cover off.  Vacuum to the distributor will increase timing advance, not decrease it.  Not sure what's going on there.

The quickest way to check the complete temperature sensor circuit is to measure resistance at the ECU connector.  Pin 13 to ground.  Then compare the value to the chart.  The best drawings are in the EFI Guide, 1980 version.  Shows the connector itself with numbered positions.

I followed he 280Z EFI book to probe the ECU pins.  Everything was correct, even the resistance to the WTS.  The only thing I can't check with a VOM  is the ignition coil pulses, but the FSM probably  tells you how to do that.

What does your tachometer do when you try to start it?  The weird timing numbers and wet plugs suggest an ignition module problem.  Too many ignition pulses (sparks).  The 280Z ignition modules seem to die at a fairly constant rate.  They're old.

Right now, the rev counter is (dead) since there is no spark from the HT wire.  The last time the engine 'ran'  the revs were really jumpy-  steady 800 a second, then blip to 14, then quit.

I agree it might be an ignition module problem.  This might be a chance to switch to the GM HEI module.

It's pretty easy.  You can do it temporarily in the engine bay as a test, before putting the time in to make it permanent.  Or just get ahead of the eventual failure and make it permanent from the beginning.  The performance is as good as the stock Nissan modules.

I did install a generic GM HEI ignition module, and it works fine;  the engine runs smoothly without backfires, but the rev counter is not responding, so I'll  look into why that is so.  If this new ignition module works out, I'll consider the performance  Pertronix one, and put the generic one in my spares kit.

Would you say all the trouble is worth  the $400 for a replacement OE ignition box?

Edited June 7, 20186 yr by TomoHawk

Weird that our last two posts from yesterday have disappeared.  About the condenser.  I added a condenser to the negative circuit of the coil when my tach wouldn't function.   It worked but I can't say exactly why.  Many people have used the HEI module with no tach problems.

This is essentially what I wrote yesterday.  I saw it post.  Good luck.

It doesn't make sense, but since the engine was operating (smoothly) I drove around the block to test it a little, then put the cover back onto the ECU, taped up the un-used  ring terminals from the distributor junction block,  and the rev counter started working.  It still needs a proper tuner some adjustments, but I  put about 12 miles on it today.