1970 914/6, No Spark at Coil (Fixed- installed MSD 6A) Options

[Joe C]

Recently replaced plugs, points, cap, rotor, wires, coil. Car was running great for about 150 miles then started to sputter like it was running out gas. Luckily made it to a gas station filled up and went on my way..... for about two miles and it just died!

This is a 1970 six with 45k miles. Its getting fuel, Points are good and correctly adjusted, CD box whistles when the key is on but there is no spark at the coil. Checked all the grounds and had my head in the engine compartment for hours looking for loose or broken wires.

Any ideas?????

And by the way, if you have classic car insurance make sure you opt in for the towing.
I didn't, $175.00 for the hook up and a 6 mile trip!!!

[johnlush]

Joe,

BTDT. In my case it was a bad ground to the CDI box. Not saying that is your issue if you've checked it but worth mentioning. Are you visually inspecting or also using a VOM to verify?

When I was chasing mine I corresponded with gentleman on the Pelican forums, Ingo Schmitz, that provided a great overview of this circuit. I have it pasted below. Not sure about the newer coils but I prefer to find an older original Bosch 0 221 121 0 001 that tests within specs.

Good luck and tell us about your -6!

John

The box has 3 pins. In addition GND is supplied to the box via its case:
1. +12V is supplied to the center pin and has to be present with ignition ON and START

2. The trigger pin puts out +12V (via a 33Ohm or 100Ohm resistor depending on vintage of the box). You can confirm this with a volt-meter against GND. When this pin is shorted to GND and short is removed (aka. points close and then open) the box is triggered to release a spark. The points in the distributor are a simple switch with one side to GND and the other to the trigger pin.

3. The output pin goes to the coils primary and the other side of the coil primary is connected to GND. This provides the charge path for the internal capacitor of the box and the output of the energy for the spark. Be careful as this pin will float up to 400V in standby if the coil isn't connected or damaged. This will get your attention when you touch there.