81 turbo crank/ dizzy question

[jturbo06]

i just bought a 81 turbo auto for 400 bucks, from what ive been reading this year has the cas on the crank pully, mine has the ring but no sensor but i do have one in my distributor, im thinking the previous owner tried to swap it? (car came with a distrubuter without the cas in the back) is it possible to get this setup to work?

[randy 77zt]

the engine probably has a 82-83 dizzy on it .i have a zxt crank sensor if you want 1.i modded my 81zxt crank wheel to a 30-1 by grinding out every 2nd& 3rd tooth.the i mounted a hall effect gear tooth sensor to run aftermarket efi system.some efi systems could read 81 zxt crank sensor

[jturbo06]

im just trying to get it running for now, can it work with this dizzy or do i need to get the original sensor? also how much would you want for it

[Brad-ManQ45]

If you have the '82/83 dizzy that's all you need.

[jturbo06]

i have it but i cant get it to work ive narrowed everything else down is there a trick to it or something?

[Tony D]

download the FSM for an 83 turbo and check the CAS (dissy) installation and timing instructions.

 

The signals put out by the 81 CAS and the 82/83CAS are identical. Either ECU will work with either CAS as long as it's phased properly.

[jturbo06]

i thought the 81 only had a signal every 4 degrees and the 82-83 and one for every degree

[Tony D]

Incorrect, the CAS units are interchangable, they give the same signals to the ECU.

They are plug-and-play interchangable.

 

I know, I've gone both ways on this at any given time. Currently I have an 83 CAS in an 81 right now.

Previously I'd retrofitted an 81 engine with CAS into an 83ZXT 2+2 and did nothing more than plug the harness in...they are the same to the ECU.

 

How they are derived is slightly different, but the signals and waveforms on the two distinct signal channels as read by the ECU are identical!

[jturbo06]

well then im just completly stumped why im not getting any spark at the coil

[Tony D]

Have you used a scope to probe the signal to the ECU from the CAS? Or are you getting a pulsed signal to the ECU from the CAS as you crank (DVOM set 0-5VDC and probing appropriate pins in the cable?)

Are you (with the DVOM range set 0-5VDC) seeing a 'pulsed' signal on the 'yellow wire' from the ECU to the Ignitor?

Can you force a spark simulating a pulse into the ignitor?

 

Time to break out the FSM to trace some wires and see where probes need to be. Until you figure out where you have a pulse, and where you don't, you're just guessing. The circuit is very simple, CAS-ECU-IGNITOR start at one end and go till you loose your signal. The last component to get a good signal but not send it out is bad.

[jturbo06]

so i dont have a scope but i tool my volt meter dont know if it will work but i cant fig out where in the fsm it tells me where to prob so i did a cont test to find the wires for the dis and ignitor to the ecu, found 2 of the 4 from the dist have 5 volts with the key on 1 has 12 volts and 1 has nothing , the ignitor wire isnt gettign anything so does that me my break is in that wire? thanks guys

[HowlerMonkey]

The 1981 sensor does output the same signal.

 

The way nissan gets 180 pulses from a 90 tooth wheel is that the sensor has three "poles" with one ending 3 pulses per crank revolution and it uses two others that are in parallel to the same signal lines.

 

The other two poles are spaced 1/2 tooth relative to each other which nets 180 pulses per crankshaft revolution.

 

It works great with any 280zx turbo ecu but won't work and can't be modded to work properly with the 300zx ecu though it should run the 300zx ecu badly because the sensor can not output the cylinder 1 identification pulse.