Spark from crankshaft pulley
 

I have a 97 3500 4x4 that has had three crankshaft sensors and one computer replaced in the last three months. I took it to a dealership for trouble shooting. They discovered a strong, blue spark arching from the crankshaft pulley to the block. When this happens the tach goes crazy. The dealership has no idea what is causing the spark or what to do. Does anyone know what this is an what to do for it?

Thanks,
nbishop

Make sure there are good clean grounds from the engine to the frame and from the engine to the cab.

I replaced all battery cables and grounds and also added extra grounds from frame to engine and tranny. Did not fix the problem

How about between the engine and cab?

I can't think of any other reason this would happen.

Is there any kind of rubber insulating the pulley from the crankshaft? Like a dampener. If there is, I can see that a static charge could build up and discharge itself occasionally. I would remove the pulley, clean it up and check that it is solid metal. If there is any sort of rubber dampener on the pulley then either replace the pulley or some add a bonding strap from the pulley to the crankshaft.

Thanks, I will try that!