Weak spark issue
 

Hi gang tried to start up the 77 911s 2.8L E cam 9.5 Webers no luck. Took a read of the plugs and found the weak spark carbon look. Also the spark test at the coil was weak and at the plug.So wanting to upgrade I replaced the old MSD6 and protronix with a MSD6al new protronix II .I checked spark at plug and still have a weak gold yellow spark that seemed late to fire.Check at coil was better than previously.PLug wires are Clewitt with 15k on them .Ive done searches and need a fresh imput from the weak spark Gurus thank in advance Chuck !.

Weak Spark.........
 

Check your main power supply for the MSD to make certain that you are getting a full and strong 12 volts or more. Your problem may be nothing more than a weak battery. Just for chuckles, check the ground wire. On my MSD setup I have the main ground going to one of the bolts holding the mounting bracket to the chassis and then on to the engine block. Use at least 12 gauge wire.

Good luck!

wild guess is that coil terminal wires are reversed or the insulation is breaking down inside the coil. Engine would then be breaking up under load.

as Fred stated the msd must receive good power and have a good ground.

Even a bad alternator could cause voltage delivery problems to the msd.