Pertronix installation, a couple issues after done 240z

[Arne]

No. Either the tach is not sensing enough voltage through the inductive loop, or it's failing. The distributor can't affect it that way, as far as I can see.

My money is on a failing tach.

[71Nissan240Z]

No. Either the tach is not sensing enough voltage through the inductive loop, or it's failing. The distributor can't affect it that way, as far as I can see.

My money is on a failing tach.

Why would it work before? I guess i should get a friend and test the voltage at the tacho is stable at 4k just to be sure then buy a new tacho.

[71Nissan240Z]

Some how I cannot edit my previous post, but on another note I opened my gap on the plugs to .045. Havent drove the car yet, but it idles and revs fine.

[71Nissan240Z]

Im buying a 280z tach, anyone know of a link to help me install it?

[71Nissan240Z]

Installed a 280z tach. It was pretty easy, the positive and negative wires on the old 240z tach are reversed on the 280z tach. And the loop is just disconnected from the old 240z tach and left alone. All you have to do next it transfer the guts of the 280z tach to the 240z shell so everything fits fine in the dash. The feed on the 280z tach needs a line going directly to the - coil on the tach. Works great, way better than the old one did.

[240ZGL]

Have you left the neg wire off the coil ? I just started mine for the first time ever this weekend. I'm running Pertronix II and the .6 ohm coil so I don't need the resistor but my hookup is power wire to the pos side of the coil. The ignition ground wire is left off the neg side of the coil. Pertronix red wire to the pos side of the coil, Pertronix black wire the the neg side of the coil. The ignition runs perfect the tach works great.

[bpilati]

Timing should be whatever worked before you did the conversion. It may be different than stock depending on your car, conditions and config. Stock is 5 degrees BTDC. I'm running about 10 degrees on mine.

With the 3Ω coil you should bypass the resistor.

My understanding is that you should not bypass the resistor to protect the tach. Someone can correct me here, and you should use the same resistance coil as the stock one.

[Arne]

In theory, I agree. I will say that my tach has not had any problems running on full voltage, but I don't plan to do that forever.

Something else to consider - Pertronix seems to recommend the 3Ω/no resistor combo, and the 3Ω is the only Pertronix coil that MSA sells. I'd prefer the 1.5Ω w/resistor myself. But since I've already had one Pertronix coil fail after VERY limited use (but beyond the warranty in time), I'm looking into a Crane PS20 instead, which is 1.4Ω and ships with its own matching resistor.

[71Nissan240Z]

Have you left the neg wire off the coil ? I just started mine for the first time ever this weekend. I'm running Pertronix II and the .6 ohm coil so I don't need the resistor but my hookup is power wire to the pos side of the coil. The ignition ground wire is left off the neg side of the coil. Pertronix red wire to the pos side of the coil, Pertronix black wire the the neg side of the coil. The ignition runs perfect the tach works great.

I believe we may have different style tachs. On the early Z cars they came in 4 wire positive feed from the coil. For some strange reason the ignition system runs through the tach as a positive feed to the coil. So converting to a 3 wire negative feed tach I had to keep one of the old tach wires in the loop to the positive point on the coil to keep my car running.

My understanding is that you should not bypass the resistor to protect the tach. Someone can correct me here, and you should use the same resistance coil as the stock one.

The total resistance is around 3ohm with the stock coil and resistor. If you get a 3 ohm coil you can bypass the ballast resistor. It has nothing to do with the tach, the resistor is used to lower the voltage to the points.

In theory, I agree. I will say that my tach has not had any problems running on full voltage, but I don't plan to do that forever.

Something else to consider - Pertronix seems to recommend the 3Ω/no resistor combo, and the 3Ω is the only Pertronix coil that MSA sells. I'd prefer the 1.5Ω w/resistor myself. But since I've already had one Pertronix coil fail after VERY limited use (but beyond the warranty in time), I'm looking into a Crane PS20 instead, which is 1.4Ω and ships with its own matching resistor.

Is the pertronix kit not reliable? It seems to me that its more of a human error issue than the unit itself (i.e. 1.5ohm coil and no BR or leaving the key to ON) I will most def look into a different company if mine fails.

Edited May 31, 2011 by 71Nissan240Z

[Arne]

The total resistance is around 3ohm with the stock coil and resistor. If you get a 3 ohm coil you can bypass the ballast resistor. It has nothing to do with the tach, the resistor is used to lower the voltage to the points.

Well, in the early cars the reduced voltage out of the resistor goes through the tach on its way to the coil. Call it ~8V through the inductive loop. Bypass the resistor and you get closer to battery voltage through the loop instead - in my car a bit over 11V, not quite 12V. Will more voltage through the loop harm the tach? I don't know. I suppose it is possible.

Is the pertronix kit not reliable? It seems to me that its more of a human error issue than the unit itself (i.e. 1.5ohm coil and no BR or leaving the key to ON) I will most def look into a different company if mine fails.

You'll hear comments both ways on whether the Pertronix Ignitor is reliable or not. There are people who have had bad luck with them, and just as many (more?) that have had no problems. (My failure was the Pertronix coil, not the ignitor.) But since I've seen plenty of failures with other solutions as well (especially the ZX ignition), I keep a set of points, related parts and necessary tools in the car at all times, just in case.

[gibson99]

can you tell me where the small condenser thaht sits on the top leads to neg or pos. I think my condensor goes to pos.

Dave

[earlyzman]

I had the exact same tach problem with the Pertronix conversion on my 72. First of all the tach is driven by current not voltage. The 3 ohm coil that you have will not drive the tach. You need the 1.5 ohm coil (available from Pertrnix) that matches the stock coil. You can leave the stock ballast resistor in the circuit which is about 1.2 ohms. The series resistance of the coil and ballast resistor is what determines the current the tach sees. You could also add one or more loops of the wire that goes through the u shaped clip on the back of the tach, but that would require a little info that I learned 40 years ago when I installed a Heathkit electronic ignition on my first Z.