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You may want to check the dizzy cap and rotor now. By having such a large gap on the testing tool, combined with the plug gap... you could have created an Arc Over and carbon traces inside the dizzy cap or rotor.  Get a magnifying glass and look for Carbon Traces jumping form terminal to terminal or even to the base of the dizzy cap. They will look like hairline cracks or a line dean with a sharp pencil. Check the rotor as well. 

And also between the Coil center tower and the two primary terminals.  Arc over and carbon traces can form there as well.

Bottom line. You probably didn't have an INTERMITTANT spark. You had a spark that found a path of less resistance... and it went there instead of through the spark tester. 

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this is the tester at the coil   The instruction on the package state that for HT spark it should be at 30.  Lawn mowers and weedwackers are 20.  

At some point I must have read a thread on how to bypass the ballist resistor because I did... I checked the voltage at the coil and I got about 5v  shouldn’t it be 12?  Or does it go in 5 and come out 12v.  I also check my battery and I’m getting 14.6v when running.  

The engine runs exactly the same with the spark tester on or off   It stumbles either way.   I think I’ve always had a spark issue but I’ve never looked into it.   

 

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As Chickenman says, try it again grounded to an actual ground. Not at the plug. If no change,  Check the cap like he says.

 

 

Im only familiar with 240z wiring. But with the ZX modification you should have the ignition wire from the tach to the positiveon the coil. I do believe it should be 12v but look into it.  There should be a second wire running from the + of the coil to the ignition module. The other terminal on the module should go to the - of the coil.

 

Edited by HuD 91gt

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I got some time today and I checked the voltage at the coil.  It’s 8 volts with the key in the on position (car not running)  and it fluctuates between 8 and 11.8 volts with the car running.   Does that seem right to you guys?  

I also made a video of the engine reving how does my engine sound to you guys. 

 

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The instructions  for your plug gapper are are wrong. That's way too much of a gap. Period... end of story. Been using these things for over 40 years. 

That is a FRACKING strong spark!!!   Both appearance and noise show that secondary side is working damned good. It only appears intermittent because the spark has found an easier path to follow than through the HUGE gap of your spark tester combined with the gap from the plug. You are using the Tool wrong, and may have damaged other components ( such as inside of Dizzy cap and rotor ) by running such a huge gap when testing. 

BTW, have you checked your HT leads with an Ohm meter yet? . Those leads look like old style OEM carbon core. They deteriorate with age. Upgrade to some good quality spiral core wires such as NGK.  

 

Edit: Here is a video from Mac Tool showing the proper way to use a spark tester and the proper gap settings. Note that he mentions that the printed numbers on the tool basically mean dick squat. This is the same  Mac Tools spark Tester that I use. Also note that the maximum gap setting that the Technician opens it up to is about one third of what is shown in your video.

https://www.youtube.com/watch?v=YNIIllZRNRw

Edited by Chickenman

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All the plug wires are “new”. Like 10 years old new. 

No damage from using the spark tester.  Cap and rotor are fine. 

Any thoughts on how my engine sounds?  

Also... anyone else notice the puff of smoke in the right upper corner of the screen?  What’s that about?

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10 year old plug wires are not new. Especially carbon core wires. Wires can deteriorate just sitting. Ozone can crack and split boots. Then you can get arc over to engine. Corona discharge around plugs is also a problem with old leads. Plug leads should be checked with an Ohm meter. Just looking at them is not good enough. 

Pull your plugs and take some High Resolution close up pictures. use a good digital camera or a good Smart Phone camera. We need sharp clear pictures. Turn the flash off. It will skew the plug coloring. Try to get some good side on shots of the center ceramic and the full view of the side electrode. A Top angled view is best. How old are the plugs? 

Plug reading will tell you a lot about the engine running condition. 

I noticed the smoke. Sounds like you have an exhaust leak. Wouldn't surprise me if  you have a leak at the exhaust manifold. Check for loose or broken exhaust studs. Also any evidence of soot around exhaust manifold or cracks in exhaust manifold.

Engine sounds noisy. probably needs a valve adjustment .  If that has recently been done, then it could indicate that rocker arms are worn.  They will wear with a horizontal line across the wiping face. If you can feel the line with a finger nail dragged across the surface, then the rocker needs re-surfacing or replacement. No amount of adjustment will get rid of rocker noise when they get that worn.  But, I don't think that's your issue though. 

It's really hard to tell how an engine runs in a video. But in general, I think your car just needs a bit of a sharp Tuneup.  It doesn't sound all that bad. But loaded up on the road could be a different matter. Carb adjustment, carb balancing can work wonders on these engines. 

Also the distributor advance mechanism tends to seize up on these motors. Both mechanical and vacuum sides must be checked for free operation. The rotor should fit snug on the shaft. I've seen after market rotors that fit very loosely on the shaft. That's no good. You should be able to take the rotor and twist it about 20 degrees in the direction of rotation. Then quickly release it and it should " Snap " back to resting position. If it is hard to rotate or slowly returns or doesn't return all the way, time to take the dizzy apart and service it. You will have to clean and lubricate the mechanical Cam and governor weight system. 

Use a Vacuum pump to check Vacuum advance. Get the FSM specs and test it. Movement should be smooth. Hold vacuum and freely return when the vacuum release. The breaker plates have tiny ball bearing in them, and these ball bearing often rust or even fall out. 

Jason Grey's distributor page has a wealth of info:

http://newprotest.org/projects/510/jasonGrayDistributor.pl 

 

Here are specs for popular Z car dizzys in Excel format:

Distributor advance curves.xls

 

 

 

 

 

Edited by Chickenman

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