ignition issues

perhaps a crank angle sensor? does the fsm tell how to test this?

When the engine is not starting, is there spark?

The appropriate FSM tells you how to test many things, including the limited tests on the CAS, and tests on ignition components such as the coil and Power Transistor.
Try disconnecting the MAF and see if the engine starts. FSM tests on the MAF can be done, but are not a reliable indicator of condition.

update...i replaced the cap and rotor, noticed poor continuity at multiple locations. replaced the coil as well. would have replaced the plug wires, but cant get em for a few days. the coil wire looked bad, and i was able to replace that. i also swapped the original ecu back in...got codes 23 and 31. 31 says ecm/ecu, and 23 isnt on my list. when i was done taking the codes, the car started right up. ran great....then died...will restart after five minutes, run for 1 to 10 minutes, and die, as if i turned the key off...no spark...no change of codes during dead time. also checked timing at tdc, everything is fine. i noticed if i pushed in on the tps plug, the rpms go up a bit...i might have bet on the coil in an older car...any input would be greatly appreciated...

plazdesign said:

i also swapped the original ecu back in...got codes 23 and 31. 31 says ecm/ecu, and 23 isnt on my list.

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Then get a better list. Do you actually have a copy of the 85 Z31 FSM?
Code 23 is TPS, and you need to do the test correctly.
Code 31 is load signal, and you need to do the test correctly.
Neither of those codes would cause a stall.

No spark eh?
Can be the CAS dying with heat, or the Power Transistor next to the coil.
Do you get injector pulse while the engine is cranking but not starting?

some great questions...it turns out, i have the 86 fsm, as at the time i downloaded it, the 85 wasnt available...and my meager common sense pointed me in the direction of the cas, or the power transducer, that the parts shop called the ignition module...both of the things you pointed out...turns out the parts store wants 275 bucks for the transducer....the cas, requires a distributor replacement,does it not? thats what my chiltons book says..i cant yet answer the injector pulse question. tell me more about this #31 "load signal". i am concerned as i mentioned about the plug and/ or wires going into the tps...i will try to download an official 85 fsm. thanks, again!

plazdesign said:

the cas, requires a distributor replacement,does it not?

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The aftermarket may be able to supply the internal bits without the entire dizzy. Junkyard parts with a warranty may be an option.

tell me more about this #31 "load signal".

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The 86 FSM covers the ECU codes adequatley. The error codes did not change until the 1987 MY.

after a night to sleep on it, i am leaning towards the coil or module being bad. the car runs great, then shuts down...no spark...five minutes later it will start up and run great again...i put a new coil in, no change. i have had bad new parts before.
could the code 23 or 31 be pointing to this? is there a test for the module? i read in here that after it dies, to pour icewater on the module, if it restarts right away then thats it...looking for a junkyard with a z to get a cheap one. i found code 23, called throttle valve switch/idle switch circuit, and 31 says load, including lights/ps pressure/fans/heater/rear defogger switches. does mean it recognizes a load that shouldnt be there?(i also read that when i push the gas pedal the the floor and back, the 23 should go away-but it doesnt)
again, thanks for the great input!

plazdesign said:

could the code 23 or 31 be pointing to this?

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No. As I wrote earlier: "Neither of those codes would cause a stall."

is there a test for the module?

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The FSM shows a continuity test for the Power Transistor. I find it simpler to have a spare from a junk yard that I can plug in.

i read in here that after it dies, to pour icewater on the module, if it restarts right away then thats it...

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I suppose a fast evaporating spray, such as brake cleaner, would do a similar job.

and 31 says load, including lights/ps pressure/fans/heater/rear defogger switches. does mean it recognizes a load that shouldnt be there?

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The load signal tells the ECU to raise the idle when there is an electrical or mechanical load on the engine.

(i also read that when i push the gas pedal the the floor and back, the 23 should go away-but it doesnt)

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You can fix that after you have determined whether there is injector pulse when the engine fails to restart. Buy a noid light from an auto parts store, they are cheap.

Get some electronic cold spray from Radio Shack and try keeping the ignition module cold....the symptom of the car dying after a few minutes is very indicative of a module defect(or a coil, but you checked that) and if keeping the module cold prevents the problem, then there ya go....Both coils and modules have an annoying habit of fritzing when they get warm from use as a first symptom of impending total failure.

1) How many miles on the car ?

2) Did you get the timing back to the original mark?

3) Agree with Ghost

4) Just to be clear.. when the car dies it's just like a key off condition.. not a stumbling.. dying ... dying ... dying.. almost dead.. poof.. dead.
( verify fuel pressure if the car stumbles as it dying )

Mike

thanks for all the responses. to clarify, it WAS dying completely without a sputter or cough, after running great for a few to ten minutes. then would not restart for five or so. now, it doesnt fire at all. no spark. i was able to get the timing confirimed okay. tested the new and old coil, same numbers, same results. 185,000+ miles. i am planning to do the timing belt soon. since ignition failed with both coils, i am leaning towards the module. trying to find a cheap one in a junkyard. is there a way to test the module? i am certain i am getting fuel, and nearly certain of the no spark. cant make the coil or spark plug wire arc to the block. if i get 12v at the coil input when i turn on the key, does that mean the module is working, and the coil is failing? what else can shut down the spark? thanks, again!

If it's CLICK dead... your coil might not be the problem still could be the CAS or the transistor module next to the car...

There's a resistance test in the shop manual for all 3

Mike

i finally got back to this...today i replaced the coil with a second new one, and voila! she fires right up and keeps running. had printed out the testing procedures for the module, etc. but decided to try it out first. seems okay...a little missing that i attribute to not having the timing set exactly right. or a vacuum issue that wouldnt suprise me a bit. now i get code 44, all clear. it still will fire against it self(best guess i can make) and stall suddenly, then be hard to restart. it runs backwards when this happens, so i again blame timing. something tells me the adventure has just begun! one other thing, i note there are three white marks equally spaced on the pulley. is this someones error, or could it represent 10,20,30 degrees? thanks again!

drove her to work today...it was like a new car...more power, better mileage, breathing easier...then....off goes the engine as i am pulling into my spot. same instant stall...no restart, no cough, no spark...had to leave it there...should have done those tests before driving it. back to thinking ignition module, will look for them in the morning...and will do those tests. sure was a pleasure while it lasted!
same question as before, how many things can cause zero spark? thanks again, and again...................

plazdesign said:

same question as before, how many things can cause zero spark? thanks again, and again...................

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The ECU figures out the crankshaft position from the CAS in the dizzy.
The ECU decides when to trigger the Power Transistor which controls the current to the coil.

i take that to mean i need to confirm both the cas and the transistor function...i have the tests for both printed out and will do them when i get back to the car...which is dead at work...wouldnt some kind of code pop up for a failure of either or both? thanks, and i will let ya know what i find.

plazdesign said:

i take that to mean i need to confirm both the cas and the transistor function

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Yes. That is why I suggested plugging in a noid light to the injector harness to check for injector pulse.
If the ECU does not receive valid CAS signals, the ECU will not trigger the Power Transistor or fire the injectors.

i have the tests for both printed out and will do them when i get back to the car

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Home tests on the CAS are generally limited unless you posess a logic probe, a CRO or some other fancy bit of gear.
I like to have a known good spare that I can plug in.

wouldnt some kind of code pop up for a failure of either or both?

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Don't bet your house on it.

latest update...got sunshine this a.m. and gave her a jump from my truck...lots of cranks, but no sparky...installed used, tested good, ignition module, no start......swapped out the ecu, which was the spare known good, and starts right up...since it died with this spare, i am not overconfidant....still, with a few timing and idle screw adjustiments, it ran well, and took me home...didnt run as sweet as it did before it died, but i am pleased non the less...like before, i am thinking the adventure is just beginning...(at least shes home, so i can test more).

turns out my lack of confindence was justified, as this morning it just cranks and cranks, with no spark...i am mystified as to how i keep getting it running and then it doesnt run...yesterday, it wouldnt start until i swapped computers, today that has no effect. i am guessing(!) crank angle sensor, but not sure...there is a local nissan specialty yard near by, and they have a dizzy for a good price, not sure if i can change only the cas. whats a noid light? do you mean a voltage test probe with a light? i am assuming the fsm will show me how and where to test....more ramblings to follow...thanks again!