Transistorized Ignition

[Blade]

I have a 1971 280SL that would not cut off when the ignition was switched to the off postion until someone shut the driver door. No correlation except for the vibration from shutting the door. The same day that the engine would not cut off the fuel pump cut on with the ignition off and we found a leak at the washer on top.We did not try to start the car again till yesterday and found that it would not start. The engine turned over but we could not get it to start. We thought it might be the fuel filter because the crimp washer had to be replaced.

All is repaired and fuell pump is working. We left the ignition on longer to make sure we had sufficient fuel flowing though the filter. While the ignition was left on the .4 ohm Ballast Resistor decided to heat up and start to smoke. I used a volt meter and checked the + side of the coil with the points closed and the ignition on and it read below .8 volts. Could this indicated the switchgear box is defective and needs to be replaced or does this indicate a short in the wire from the resistor to the switchgear??

Rewind two months ago and my mechanic found that they had wired around the switchgear box and the points kept burning. Would you change the system to electronic ignition and if so what kind??

[jeffc280sl]

Jim,

Have a look at this post.  It pretty much describes your situation with regards to engine run on.


http://www.sl113.org/forums/index.php?topic=4019.0

Attached you will find a wiring diagram and test procedure for the transistorized ignition.

Use the search function and look for posts related to 123Ignition, Pertronix and Crane for alternate ignition systems.

[Blade]

Jeff

Thanks for the link on why the engine won't stop running due to brake fluidl. It was definately the same problem. Now why is the relay melting itself and the car not starting?jim

[jeffc280sl]

Jim,

If they wired around the transistorized ignition box then the prior owner must have installed another ignition system.  The MB ignition box is located under the battery.  It's very difficult to trace wires with the battery in place.  I suggest you remove the battery and look under the battery tray and see how the ignition system is wired.   I would start tracing wires and see what has changed from the wiring diagram that I attached to the earlier post.

[Blade]

Jeff

Thanks again, I'll pull the tray out Monday and see what I can find.

Jim

[Blade]

Jeff

I found the short on the lead coming off the ignition module. It was shorting against the sheet metal where the resistor was attached. Connector had bare wires.

jim