l6 250 ignition

[50bomb]

We got the l6 250 to start with one turn of the key a month ago. But ran into a cracked transmission pan. Finally got that all in and new intake and exhaust gaskets. It fired up after a couple tries and then dies after a minute or less. So we let it cool down and tried it again and when it fired up we tested the Ignition coil with the light tester and the Positive shows GOOD but no light on the Negative ground. DOes this mean that it is burning out and needs replaced? Hope this makes sense. Thank You.