Lumina DIS fuse blows

My son's 90 Lumina (3.1L) died while driving with no previous issues or warning. After pulling it home we found the 10amp DIS fuse was blown, and blew the replacement. Noticed the fuse blew when the key was turned to "on" and before engaging the starter. Engine turns over fine, and all the lights/guages seem to work. Replaced the plug wires as they were badly scuffed in places, but no help. Replaced the key lock cylinder as it was very sloppy (found broken gear), but no help with fuse problem. Since the steering column is disassembled we have access to the ignition switch, but before guessing any more, hoped to get your suggestions. Thanks for any help!

My standard comical answer...put a 50A fuse in it and replace whatever catches fire ;)

Try disconnecting the wiring harness at the DIS and see if it still blows the fuse when you turn it on.

That module and coilpacks are up on the core support on yours, they can eat a lot of water in certain circumstances. Was it raining or anything when the trouble started?

Thanks for the speedy reply! Just tried removing the DIS wiring harness, and the fuse still blew when key turned on.

No rain or condensation problems when the trouble started.

Check owner's manual, see what else is on that circuit (if anything).

So you know the problem isn't in the module or coils...I think your CPS has it's own fuse...so that shouldn't be it.

Hmmm.

Maybe have to hunt that DIS harness down back to the ignition feed and look for a short.

Pretty hard fuse blow? (spark, pop, etc?)

Tried the CPS and that did the trick for the blowing DIS fuse! The car won't start now though. Fires a little but won't quite catch. Checked for spark and does have spark at the left and middle of the 3 front plugs. Switched plugs and wires to make sure it's not a bad plug or wire on the right position. Possibly a bad coil pack in that position?

huh? what do you mean tried the cps? do you mean you unplugged it and the fuse didn't blow anymore? if it is unplugged your car will not run at all.

Sorry, poor choice of words. I meant I replaced the CPS. Car is running now, but sounds like not on all cylinders, and doesn't have full power. My son was happy to have it running at all, and had to go to work, so tonight we'll see which cylinders aren't firing.

could be a bad coil pack. Like you said, see what cylinders are firing, and if there are two that arent that are on the same coil pack, that is likely your problem.