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!!!

[Retroracer]

Couple of suggestions:

1) check the polarity of the low volts side coil connection; the effects of getting this backwards SHOULD be more subtle than you are describing, but no harm checking
2) If you still have the old coil you replaced, try swapping it back IN. If you then get spark, then that could be an early life failure on the new coil

Depressingly: The 3-pin CDI can fail in ways where the HT circuit is still whining away but does not trigger. Good luck!

- Tony

[Joe C]

Thanks Tony,

Already tried the old coil and no luck. Just read a bunch of negative reviews on the Bosch coils made in Brazil. Maybe the new one is also bad..

[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.

[porschetub]

Tony and John are dead on with replies,the bosch 3 pin can buzz but still have issues , these units are so old now and prone to failing,when researching my system I went for the "blue" (75 911 MY ) Permatune which is known to be very reliable,however they require a matching permatune transformer coil which is rather spendy ,I was lucky to find a NOS unit for sensible money on Ebay.
Ashlocktech offer a rebuild service for the Bosch CDI's which compared to risking buying secondhand is a good option @ $279 with your core , good price really.
Pretty sure you need to match the coil to the CDI you have also.
Good luck.

[dakotaewing]

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!!!

Don't use your insurance to simply tow your car when it breaks down. Counts as a claim against your insurance policy! Get AAA instead.

[IronHillRestorations]

Make sure the CD box is plugged in good, and has a good ground, if it's got corrosion on the ground it won't run right.

Check voltage or continuity on the CD box wires. "A" goes to the coil, "B" is switched 12v, and "C" goes to the distributor.

I've done two 6 engine harnesses in the last couple years that had failed wire. I'm not saying that's the problem, but you've got a 50 year old car.

Are you sure it's ignition? One thing I've learned is about half of ignition problems are fuel problems, and about half of carb problems are ignition problems (IMG:style_emoticons/default/smile.gif)

[Superhawk996]

One thing I've learned is about half of ignition problems are fuel problems, and about half of carb problems are ignition problems (IMG:style_emoticons/default/smile.gif)

(IMG:style_emoticons/default/agree.gif) So true!

[Superhawk996]

One thing I've learned is about half of ignition problems are fuel problems, and about half of carb problems are ignition problems (IMG:style_emoticons/default/smile.gif)

(IMG:style_emoticons/default/agree.gif) So true!

Darn duplicate post for errarnt double click.

I'll add this since I'm editing anyway.

1/2 of the ignition and starting problems are grounding problems.

[rgalla9146]

^ (IMG:style_emoticons/default/agree.gif) with Perry

Check for gas from the accelerator jets
Check ignition at the points

[Joe C]

Make sure the CD box is plugged in good, and has a good ground, if it's got corrosion on the ground it won't run right.

Check voltage or continuity on the CD box wires. "A" goes to the coil, "B" is switched 12v, and "C" goes to the distributor.

I've done two 6 engine harnesses in the last couple years that had failed wire. I'm not saying that's the problem, but you've got a 50 year old car.

Are you sure it's ignition? One thing I've learned is about half of ignition problems are fuel problems, and about half of carb problems are ignition problems (IMG:style_emoticons/default/smile.gif)

Carbs were just done. I checked and cleaned every ground. It’s looking like the CDI box. Box is getting power (12v). But nothing going to the coil.

[porschetub]

^ (IMG:style_emoticons/default/agree.gif) with Perry

Check for gas from the accelerator jets
Check ignition at the points

Or hook up a timing light on #1 and see if it flashing,a basic way of discounting a CDI issue if the points are set right and provided electrical connections are ok as Perry mentioned.
I don't know how you would set points accurately in a stock 914/6 ?,without a firewall cutout it must be a total PITA...just saying cause I don't have points anymore and a firewall cutout.

[porschetub]

Make sure the CD box is plugged in good, and has a good ground, if it's got corrosion on the ground it won't run right.

Check voltage or continuity on the CD box wires. "A" goes to the coil, "B" is switched 12v, and "C" goes to the distributor.

I've done two 6 engine harnesses in the last couple years that had failed wire. I'm not saying that's the problem, but you've got a 50 year old car.

Are you sure it's ignition? One thing I've learned is about half of ignition problems are fuel problems, and about half of carb problems are ignition problems (IMG:style_emoticons/default/smile.gif)

Perry could the OP bypass the CDI and test run without a condenser?,thinking it would be the best test to confirm a bad CDI ? ,interested in your answer,cheers.

[IronHillRestorations]

Make sure the CD box is plugged in good, and has a good ground, if it's got corrosion on the ground it won't run right.

Check voltage or continuity on the CD box wires. "A" goes to the coil, "B" is switched 12v, and "C" goes to the distributor.

I've done two 6 engine harnesses in the last couple years that had failed wire. I'm not saying that's the problem, but you've got a 50 year old car.

Are you sure it's ignition? One thing I've learned is about half of ignition problems are fuel problems, and about half of carb problems are ignition problems (IMG:style_emoticons/default/smile.gif)

Perry could the OP bypass the CDI and test run without a condenser?,thinking it would be the best test to confirm a bad CDI ? ,interested in your answer,cheers.

You can run without a condenser but it will cook the points. I really don't know how to test a CDI box, except for the whine sound, and swapping out.

[IronHillRestorations]

Check the distributor cap and make sure it's still got the center contact inside. I've had trouble with that years ago. The carbon contact wasn't installed right at the factory and came out, it was running on the spring which didn't last long

[ClayPerrine]

This may help you..

(IMG:http://www.914world.com/bbs2/uploads/post-1143-1155174537.jpg)

It is a simplified wiring diagram for the CDI ignition on a 914-6/911

The funky clear dashed wires are the shielding for the wiring. They are grounded to the engine.


Clay

[johnhora]

Also I've found the early CDI boxes don't like regular coils...ie Bosch Blue etc. will burn them up.

The OE PN needed is 90160250200 - Bosch 0-221-121-001

[ClayPerrine]

Also I've found the early CDI boxes don't like regular coils...ie Bosch Blue etc. will burn them up.

The OE PN needed is 90160250200 - Bosch 0-221-121-001

(IMG:style_emoticons/default/agree.gif)

Definitely. Don't use anything other than the factory coil. The factory actually calls it a "Transformer" rather than a coil.

[Joe C]

^ (IMG:style_emoticons/default/agree.gif) with Perry

Check for gas from the accelerator jets
Check ignition at the points

Or hook up a timing light on #1 and see if it flashing,a basic way of discounting a CDI issue if the points are set right and provided electrical connections are ok as Perry mentioned.
I don't know how you would set points accurately in a stock 914/6 ?,without a firewall cutout it must be a total PITA...just saying cause I don't have points anymore and a firewall cutout.

Setting the points is not easy. you bend and twist in ways you never thought were possible!!

[rgalla9146]

^ (IMG:style_emoticons/default/agree.gif) with Perry

Check for gas from the accelerator jets
Check ignition at the points

Or hook up a timing light on #1 and see if it flashing,a basic way of discounting a CDI issue if the points are set right and provided electrical connections are ok as Perry mentioned.
I don't know how you would set points accurately in a stock 914/6 ?,without a firewall cutout it must be a total PITA...just saying cause I don't have points anymore and a firewall cutout.

Setting the points is not easy. you bend and twist in ways you never thought were possible!!

Actually it's far easier and certainly more accurate to remove the distributor
to adjust the points and therby the dwell.