Oldsmobile/Buick Repair: Weak\No Spark in plugs, spark plug wire, jumper wire

Question
My truck suddenly stopped starting and was starting weak that day. It hasn't started since. It is a 1980 Chevy C-10 Scottsdale. The fuel filter was just replaced, thinking it was the fuel filter, but no success. When I hold a spark plug to the block and have my son turn it over there is a very weak yellow spark. The battery is good, but the ground connection has a slight crack in the tin connection piece. It still has full contact though. The corrosion was removed.
My niece is also having a similar problem - the fuel filter was replaced because it had never been replaced in an 86 Buick Century. The plugs, wires, and distributer\rotor are less than a year old. When we try to test the spark on it we see no spark at all. Her connections are good, and a fully charged battery.
Could it be that coil has gone bad (again) on these vehicles, or is there another cause for these symptoms?

Sincerely,and thanks for any help in advance;<br>Clayton Aaberg

Answer
Hello Clayton,
Sure, it is possible that both of the vehicles need a new coil, but it is every bit as possible that different problems plague each of the vehicles, so each should be tested and repaired individually.
On the truck, that has a carb, so see if gas is squirting in when you press the pedal.
Try a new spark plug wire, if those are several years old. Also, if you are checking the spark with a spark plug, make sure it is a good one, or just use a jumper wire to ground, and check spark to it.

1980...gee, does that still have points? I would suspect it has HEI,(High Energy Ignition), so with any spark, the module is probably good. Wires, rubber washer under the coil, or the coil itself is what I would concentrate on.

On the Buick,...carb also. But NO spark?
See if there is power to the red batt wire going to the distributor cap Batt connection when the ignition switch is in run. If not, look for a blown fuse or fusible link, or check the ignition switch.
I believe the fusible link is the one that runs the ignition switch, so if it is cranking over, that link is probably good, but i wouldn't swear it's the same one.
But the red wire needs power, in both run, and while cranking. Check both ways, because I have seen the switches open that wire while cranking.

Van