240z Pertronix Ignition Not Sparking

[Donairs]

Hello all,

After finishing my valvework on my 1971 240z, I went to start it up only to find that the coil was not sparking. Although the coil was recieving a full 9v when the key was turned to the 'on' position, when it was turned to the 'start' position, the voltage would fluctuate between 6 and 7 volts. After replacing the coil to no avail, I attempted bypassing the ballast resistor (I have been told it is not needed with an electronic ignition setup) and still do not see any improvement.

At this point I have hit a brick wall, I've tried everything I've read online yet I still fail to recieve a full 12v while starting. What else could be the culprit besides a coil? I'm no mechanic, the only experience I have with cars is the work I have done to my own datsun.

For reference, my wiring is set up exactly as the attatched photo shows. Any an all help would be greately appreciated,

Don.

[Zed Head]

Either your battery is dead or you have a big draw at the point that you're measuring voltage. With the key on, and the engine not running, you should measure battery voltage at the coil. Voltage won't drop unless current is flowing, which it should not be doing with the engine not running.

Dead battery seems most likely here. What is its voltage, measured at the battery terminals?

Edited July 14, 2013 by Zed Head

[Donairs]

Battery terminals are reading 12v. The way I've come to interpret it is the ballast resistor drops the voltage at the coil down to 9v when the key is in the 'on' position, and when the key is turned to the 'start' position the resistor is bypassed and 12v are sent straight to the coil. However, this isn't the case for me. Instead of the voltage being raised, it instead drops.

Come to think of it, even with the resistor bypassed, I still only read 9v at the coil.

Edited July 14, 2013 by Donairs

[Zed Head]

The coil, both sides, should always measure battery voltage with the key on. Voltage drop happens when current flows, when the volts are used to do work (resistance is work). The ballast resistor is designed to drop the voltage to the coil when the engine is running, but it's bypassed when the starter is used to counteract the voltage drop from the starter motor. If you're measuring 9 volts with just the key on you have a short somewhere, because no work should be happening, since the coil circuit should be open. When the engine is running, there is current flow through the coil as the circuit is closed and opened to create spark.

In short, after my rambling, your ignitor might be bad, apparently the early ones do that, shorting the coil to ground all the time. If you disconnect it from the negative post of the coil, you'll probably see 12 volts at both sides.

[Donairs]

Ignitor as in the Pertronix unit? What could have caused that?

[beermanpete]

The voltage at the coil should rise to the battery voltage when the key is in the start position. If it does not the ingition switch might be bad. The ignition switch is suppose to bypass the ballast while cranking.

Have you tried connecting the coil and Pertronix directly to the battery, bypassing the iginiton switch and wiring? Perhaps it will start that way.

[Donairs]

Thanks for the replies, I just replaced the pertronix unit and attempted running it both with and without the ballast resistor, still nothing. I would try wiring the coil and ignitor straight to the battery but I'm not sure how to do it besides sticking a piece of speaker wire to the positive battery terminal, and sticking the other side to the positive coil terminal. Will this work?

Also, something interesting I've discovered is that when the coil first receives power (as in the key is switched from the off position to on), a single burst of spark is emitted from the coil wire. Same thing happens when the key is switched from on to off. This is the only possible way I get any spark from the coil at the moment.

Also, Pete, wouldn't bypassing the ballast resistor solve an ignition switch problem as the switch is no longer diverting power to the resistor, but instead is now directly powering the coil with a full 12v?

[grannyknot]

Don, I have an L28 engine in my 70/240z but I'm using the 240 distributor and the Pertronix module.

The only combo I found to work was to take the G/W and B/W wire that had the ballast resistor between them and connect them together, then the long B/W wire from the tach goes to the Pos side of coil (just the way you have it now)

Then red wire from Pertronix module goes to Pos side of coil as well and black wire from Pertronixs module goes to Neg side of coil. Very important that the coil is a 3.0 ohm unit not the 1.5 ohm unit needed for the ballast resistor.

Give that a try.

[Donairs]

That's essentially what I do when I attempted to bypass the resistor, it never yields me any results leaving me with very low voltage at the coil.

[Lazeum]

You can really disconnect your coil & dizzy from your car to perform checks.

If you read 6-7V with ignition on "start" & 9V with ignition in "on " position, your problem is elsewhere. You do not need to bother with distributor or coil (yet!)

First you can disconnect the wire from the starter to avoid it to crank the engine during trials.

Then you need to find why you have a delta between battery and tension at coil.

Wires from the coil go to the main harness, thru the firewall below your battery. right behind firewall inside the cabin, you have plenty of connectors, make sure they are clean, here's your first source for corrosion. Check the voltage here. Wires to be checked at Black with white strip and black with yellow strip (see diagram to be sure which one is for "start" & which one is for "on"). Are voltages the same than the ones at coil / ballast. If yes, issue is not under the hood.

Wires go from the connectors to the tachometer (only the one for "on" position), then to the ignition switch then to fuse box and finally to the battery. Check voltage at those points and see where the drop occurs (most likely ignition switch or fuse box)

You absolutely need to get 9V & 12V before sorting anything else.

Low voltage means resistance somewhere unexpected. Resistance x Intensity² = heat! & less voltage to get same power means more Intensity = more heat also!

It seems issue is limited to "start" ignition position, so it is only for a short time period.

Another check you could do it to measure voltage at starter solenoid. If you read also 6-7V, I would check ignition switch in priority.

Edited July 22, 2013 by Lazeum

[beermanpete]

Thanks for the replies, I just replaced the pertronix unit and attempted running it both with and without the ballast resistor, still nothing. I would try wiring the coil and ignitor straight to the battery but I'm not sure how to do it besides sticking a piece of speaker wire to the positive battery terminal, and sticking the other side to the positive coil terminal. Will this work?

Also, something interesting I've discovered is that when the coil first receives power (as in the key is switched from the off position to on), a single burst of spark is emitted from the coil wire. Same thing happens when the key is switched from on to off. This is the only possible way I get any spark from the coil at the moment.

Also, Pete, wouldn't bypassing the ballast resistor solve an ignition switch problem as the switch is no longer diverting power to the resistor, but instead is now directly powering the coil with a full 12v?

Bypassing the ballast will only help if the problem is with the START position.

From what I get our of comments you get one spark when you turn the key on and another when you turn the key off. This suggests you are getting power to the coil and Pertronix. Perhaps the Pertronix is bad or there is a problem with the magnetic piece you placed over the points cam.

Yes, you can use a piece of speaker wire directly from the battery positive to the coil and Pertronix. That is what I would do to eliminate the primary wiring from the equation. The result will provide direction on where to focus your efforts.

[Zed Head]

beerman makes a good point. Everything is there to create a spark but the ignitor is not making and breaking the circuit.

Re-read thread and it seems like your coil negative post is grounded all the time. You either have too many wires connected to the negative post or you have a short to ground on the wire to the negative post or the module is damaged. That would explain all of the symptoms, except maybe the spark when the key is turned on. I would focus on the wire to the negative post and any place that it goes.

This link might help too - PerTronix Instruction Manuals