Quote:
Originally Posted by Jeremy911T
Yesterday I created a post about an ignition problem I am having. Thank you for all those who commented. I have now run all the tests I know of and still cannot find the culprit. I have a 71 911T with Zenith Carbs and a Marelli distributor. It underwent a complete restoration in the late 90’s and recently came out of a 3.5-year hibernation. After some initial work rebuilding the carbs and getting the some the brake work done, it ran great for a few days. Then the CDI unit went bad, had it rebuilt, and again ran great until 2 days ago. After a 10 mile trip I went to restart it after lunch and it wouldn’t fire up. The engine would turn over fine. Waited 20 minutes same thing. Had it towed home and pulled off the fuel line and the pump was pushing plenty of fuel. Checked for spark and nothing.
I pulled off the distributor cap and when I toggle the advance the points are opening and closing. I also ran some fine grit sandpaper gently over them just to make sure they were clean.
|
If you put an ohm meter across the point and crank the car, does the meter go from 0 to infinite ohms? Report findings.
Quote:
I read 12 V at the center plug on the CDI with the ignition on.
I performed the telegraph test-> no spark.
|
If the points indeed opening and closing (see above), then you have a bad signal wire from the points to the CDI, a failed CDI, a bad signal from the CDI to the Coil or a bad coil.
Coil: Measure the resistance/continuity between the two outer terminals on the coil and between each of the outer terminals and the high tension tower in the middle of the coil. Report findings. Per the Porsche Factory manual the CDI puts out about 400v. The coil Primary resistance should be 0.4 to 0.6 ohms, and the secondary is 650 to 790 ohms.
Check continuity of the wire between the points and the plug that connects to the CDI. Center is power. On one side is the wire to the points and on the other is the wire to the coil. Report findings.
... until this is addressed the rest of the tests are meaningless.