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baggedgoods

Faulty CAS?

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Hey guys, would a faulty cas still read cranking rpms but cause no spark? I've put a megasquirt in my car and am seeing cranking rpms but am having no spark and am trying to narrow everything down as best I can.

 

If so, is there any plug and play alternatives for the 1985 300zx turbo crank angle sensors that would be more readily available that I can just drop in.(I don't really want to wait up to two weeks for a $200 crank angle sensor)

 

Edit: had the car running and driving for a few days when it suddenly died and now it has no spark.

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Do you get injection?  Might tell you if Megasqurt is at least using the CAS signal to get half the job done.

 

You can remove the distributor and turn it be hand to listen for injectors clicking.  You can also get another CAS, like from a junkyard, and plug it in and spin it by hand to see if you get spark.

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I haven't manually checked the injectors themselves but I smell gas so I know there must be fuel coming out of them. The junkyards around here are bogus and not worth it. (Not an open yard and takes them a month to get something miniscule) I have a new one on the way that will be here Thursday. This no spark issue has been bugging me for awhile. The last thing I'm suspecting is a faulty ground wire to the coil. Pin36 out of the Megasquirt. I haven't been able to do a continuity test on it yet, but will do so. I've already replaced the bip373 power transistor inside the board, ignition coil, wires, plugs. The cap and rotor look fine. So I'm down to a faulty CAS, a faulty ground wire, or something else inside the board.

 

Also, I've heard the z31 cas tends to go bad after a couple years so putting a fresh one in isn't a bad idea either.

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The bip373 IS the ground wire for the coil.

 

If you test the CAS by pulling it and spinning it by hand you can hear the injectors clicking, because there's no starter motor end engine noise.  I've tested a CAS that way by plugging it in to my Pathfinder harness.  Turn on the key and spin and you should hear them clicking.  It's kind of cool.

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Yeah, you're right. I'm talking about the physical wire from the negative side of the coil to the megasquirt.

 

I'll have to test my injectors. So if megasquirt is firing my injectors, it should be controlling, or at least trying to control the spark. And if I do not have a spark but my injectors are firing, then the problem lies elsewhere than from the cas.

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If the CAS was dead, you'd have no tach input (engine RPM information) into the ECU - so, no RPM information in the software.  If it was sporadic, you'd have a sporadic RPM reading (and (should have) sporadic spark).  Those optical modules were found in every Nissan of the period - don't need to search for a Z31 Turbo CAS...  But I doubt that's your problem.

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