New purchase, no spark!

[240sxOwner]

I recently found a 90 300zx Base for my nephew that doesn't run. Long story short i have done so many builds on my 240 that taking on a mechanics special didn't give me pause at all. We quickly diagnosed there was no spark. I did as much research as possible to learn about the 300. The car already has the 2nd gen PTU. We checked and cleaned all of the grounds to the plenum. I checked the coils using my multi and they seem fine. I pulled the CAS and did the multi check from the back of the connector and everything checks out! However when we manually turn the shaft we only get one click from near the battery which im assuming is a fuel solenoid. We cleaned all of the connectors and voila we got all injectors to click and our plugs sparked. We put the CAS back in and it went stone cold. Ive pulled it back out and tested it manually and i havent had any luck since. I ordered a new CAS and plugged it up today, Nothing different. I made sure the battery had plenty of charge as well. My nephew pulled the codes before we started taking it apart in the beginning and it threw the code for the CAS. Any help would be greatly appreciated. I was so certain it was the CAS that i am now left scratching my head . Thanks in advance!

[Ozzie]

Just spit-balling, and may be things you have already checked...
Fuses?
Possible dead PTU? (even though it's a 2nd gen)
Hidden engine immobiliser?

Does it still crank, or is it dead-dead?
If not cranking, try bridging the starter with a screwdriver. Could be a dodgy ignition switch?

[240sxOwner]

Yes the car turns over just fine. We have checked all of the fuses and links. I did check the resistance on the PTU with the info I found from the 94 FSM. One way of checking it didn’t work, however the secondary check worked. I just ordered another PTU and harness so I could rule that out. Which wires to the PTU should have voltage? I haven’t been able to find anything to check the wiring to and from the PTU.

[Ace2cool]

Clean CAS connector as well. If it was an issue that was cleared, and then reappeared when the CAS was moved, then it's probably a bad CAS or bad connector. I replaced my wiring harness because the CAS wires were broken and I had to wiggle the connector to make it work consistently.

[240sxOwner]

Yea I did the best I could without pulling the female pins out. I wiggles it around and held it at all different angles. With the CAS plugged in I did the voltage check. On both the 1 and 120 degree signal wires I got 5.2v max and .2 min as I turned the shaft. I got battery voltage with the third and it would bump up/down about 1v while turning shaft. The last wire I believe is a ground and that one checks out fine with the battery and the rest of the connector.

I’m assuming the PTU is directly responsible for delivering the spark to the coils so I’m hoping by trying a new PTU and harness that does the trick. Anything else responsible for spark I should check?

Thanks for the replies it’s greatly appreciated!

[Ace2cool]

The PTU sends the signal to the coils, yes. Just CAS, ECU, and PTU really aer responsible for all things ignition timing.

[240sxOwner]

UPDATE:

The car is running and it purrs like a kitten. We cleaned the connectors really well and i believe it was one of the PTU connectors on the car side. My nephews face was pretty cool to see. Thanks for all of the help guys. Now my 2nd Nissan you all have assisted in repairing. Im sure this wont be the last time i ask for help. Thanks again!

[DCaff300ZX]

That's great to hear!
Moving forward, realize that corrosion of the various connectors is a known issue and WILL be a problem with various connectors and such- things like starter solenoid and other sim items.