Ignition old style

[mike.bike]

Hi everybody. I have had so much trouble finding the fault of why my 911 2.7 1975 wont give spark. First i am getting everthing to old style basics. So i have removed my MSD/Cdi and am going to start from scratch. I just want it to get it started! I have put new breakpoints in and a new condenser. My problem is when i put plus on + coil and _ to on coil to breakpoint and condenser, it blows the fuse? I have ground on engine to battery -. I have power from ignition to coil +
1. Does it need a resistor from ignition to plus on coil?
2. When i take the breakerpoint cable from the condenser spade and only have power from coil to condenser, fuse is ok.
3. When i connect the breakerpoint wire to the condenser fuse goes.
4. What am i doing wrong
Hope anybody can help . Cheers from Michael

[HarryD]

You are installing a Kettering Ignition System. Be aware:
1-At high rpm the system will not generate an adequate spark
2-the coil for the CDI will work but is not designed for this service. If you keep it as a permanent solution, you need something like a Bosch Blue Coil.

Here is the wiring diagram:

[Bob Ashlock]

You MUST NOT use the original CDI coil! It has only 0.5 Ohms primary resistance and is therefore drawing 24A when the points are closed. Thus the blown fuses. And it does not have enough inductance to store energy to create a decent spark. Get a "Blue coil" with 3 Ohm internal resistance. Typical Porsche 912, VW, etc. And make sure to add a condenser to control the arcing to preserve the points. This will att least get you running.

[HarryD]

Originally Posted by mike.bike

Hi everybody. I have had so much trouble finding the fault of why my 911 2.7 1975 wont give spark. First i am getting everthing to old style basics. So i have removed my MSD/Cdi and am going to start from scratch. I just want it to get it started! I have put new breakpoints in and a new condenser. My problem is when i put plus on + coil and _ to on coil to breakpoint and condenser, it blows the fuse? I have ground on engine to battery -. I have power from ignition to coil +
1. Does it need a resistor from ignition to plus on coil?
2. When i take the breakerpoint cable from the condenser spade and only have power from coil to condenser, fuse is ok.
3. When i connect the breakerpoint wire to the condenser fuse goes.
4. What am i doing wrong
Hope anybody can help . Cheers from Michael

Are your points gapped correctly and you can see them open and close when you crank the car? Have you done the following:

Originally Posted by HarryD

Check your points to be sure they are opening and closing.

Lots of threads on this topic. Here’s one:
How do i check a coil with a timing light??

To get a spark to the spark plug in the engine. Several things need to happen. First, you need power to the CDI. Next you need to have a way to trigger the CDI (the points do this by opening and closing). Then the CDI will then send a pulse to the coil which will increause the voltage and send it through the high tension lead to the rotor and to the selected spark plug. You need to verify that each step in this chain is working.

1) Verify that the CDI is getting power.

2) Verify that the CDI is producing power to make a spark. You can do this with a "telegraph" test. Take the high tension lead off of the center of the distributor and put a spark plug on it. Ground the threaded part. With your plug attached to the center lead, open the distributor, remove the rotor, place your key in the run position, and manually open and close the points. Each time you cycle, you should see a spark from the plug. If you do not, you may have a bad CDI.

3) Verify that the coil gets a signal when you crank. Replace the rotor and distributor cap. Leave the plug on the center high tension lead. Crank the engine. Do you see a spark? If so, you are getting spark to the distributor. If not, your point gap may be off or there is some other problem with the connections.

4) Verify that the spark goes to the spark plug wires. Reattach the center lead to the distributor. Attach you spark plug to one of the leads going to the cylinder spark plugs and ground. Crank engine. If you see a spark you may have a timing problem. If no spark, you have a problem with your rotor or distributor cap or your wires are improperly seated.

Do a search here as there are many threads on this topic. Look especially for the ones by early_s_man. Warren (RIP) left a great deal of knowledge on troubleshooting this problem.