"proper" use of jumper cables

[tw]

Originally Posted by Griff

I bet you're clamping to something that looks like it is bonded to the block but isn't.

Once cables have been attached, then move / shake the clamp on engine block. If cables are making a sufficient connection, then that movement will create some sparks. If the block has some sealer or paint, or if one of those connections on the battery is not sufficient, then no sparks when the cable is moved.

That sparking will also 'clean' the electrical contact.