Trouble Shooting CDI

[Swank911]

Could anyone tell me if I have the key in the on position, should I have power at one of the Pins on the CDI?

I have a 73 911e, originally MFI, with a 1980 3.0 CIS, wiring harness and CDI came with the engine. I am working with 2 different wiring diagrams. I think I have how my mechanic cut everything in, But I can not get the car to start, I want to start with the CDI then work my way toward the plugs.

With the wiring harness unplugged, I do not have any hot power into the plug. I have confirmed connectivity on the Red wire and white wire to the coil, the purple black is the tach lead. I have brown (ground) and green (?) in the plug.

Wiring diagrams show the coil getting its power from the CDI on red and white, discharging to the rotor.

Where is the CDI to get its power? Wiring diagram shows from the battery (through several connectors and all) but the only red I have feeds the coil.



Any help would be greatly appreciated.

-Jon

[James Brown]

Jon, I think the fuel pump has to be running before the CDI gets power. you must jump the fuel pump relay first. don't have the schematic in front of me now but try a search for that. Have a fire extingusher in front of you first!

[Tom F2]

Jon, I also have an early car with a 3.0 conversion. You should have power to the red wire at the CDI box, with the ignition in the on position. Disconnect the fuel pump, first, (two pin connector, front right side of engine bay), and see whether you can hear the CDI box whine. If not, then disconnect the six connector plug from the CDI box, and see whether you have power to the red wire.

Do a little searching on this board, you'll find lots of info about trouble shooting the CDI system. The only wrinkle is that your car will have couple of wiring changes, to make the 3.0 work.

[Helmsy]

Sorry to hijack this thread but I have a 930 which didn't want to start on the weekend and I tracked it down to not having any switched power to the CDI.

Where does the CDI get its power from (red wire white stripe) and is it not fused? Some diagrams show it coming from the alternator. Is my alternator/regulator/diode broken?

All fuses and pumps work fine. Just no spark and no power to the CDI.

[Helmsy]

Nevermind. I found the power comes from a fuse in the front of the car but via the shutdown delay relay. Jumpered the terminals and found the relay was bad.