i have an81 c3, and ran fine until the other day, i had to jump it and it ran for a while but when i shut it off and tried to start again it wont stay running, cranks and runs in the start position but in the on position it wont stay running. help please. harry

Sounds like an ignition switch malfunction, or a break in the ign feed wire somewhere.

And how would Harry go about cyphering out which is the persistant problem?

Sounds like a combo of ignition and security problem to me.  I never have had that problum bafore !!!

[QUOTE=Tuxblacray] And how would Harry go about cyphering out which is the persistant problem?
[/QUOTE]
Glad ya axed...
Sorry for not giving mo info earlier...I had to git back to werk...

To check for an ignition switch/wiring problem, check the voltage on the large red wire going to the "Batt" terminal on the coil/distributor cap(it should be an HEI system).
There should be 12v there when cranking AND in the "Run"(on) position. If there is voltage there while cranking, but not in "Run", I would suspect the ign switch, or the wiring from the switch to the cap.
If there IS voltage there in "Run", then we've got something else going on.

[QUOTE=harry sizeland] i have an81 c3, and ran fine until the other day, i had to jump it and it ran for a while but when i shut it off and tried to start again it wont stay running, cranks and runs in the start position but in the on position it wont stay running. help please. harry[/QUOTE]

Why did you need to jump it? That could be a clue. If you left the key on for some reason, that may have burnt the ign module( in the distributor).
There are a few threads on checking the ign module here, so we may need to re-visit them for that problem.

Have you checked anything yet, like, is there fuel in the carb, or spark at the plugs? Have you unplugged the flat, 4 wire connector on the distributor to see if it would run that way? This is the computer controlled timing, which really shouldn't act the way you describe, but, anything is possible. I've seen several that wouldn't start with that connector plugged in, and they all wound up needing a new ECM.

Check the voltage on the red dist. wire first, and make sure there is fuel in the carb, and let us know what you find, and we'll go from there.
Welcome to C3VR, btw!


Also...I don't think the anti-theft system will kill the ignition power on the '81. I could be wrong, and I haven't looked at the wiring diagram, but I think the anti-theft would keep it from cranking at all....I will look, tho. Adams' Apple2009-03-09 20:01:24

Now thats moooooch better! Even us old dawgs kin be teached a few new tricks....

Thank ye kindly Jethro!

thanks everyone for the help. I did ck first to make sure it has getting gas, no problem there. the reason i had to jump it was lack of running it for a least a month and an old battery. I store it in a freinds garage and due to the winters here in iowa i didn't get over to start it lately, it just growled. I jumped it and it fired right off. I drove it around a few block and then to my house and had planned to charge the battery. when I went out to move it again it started acting up, it would crank and start but as soon as i let up on the ign sw. it would die. i went and bought a new battery which it was due for and it cranks strong but the same thing still. one time it did start and run rough like only on 6 or so enough for me to move it under my car port and then it died. I ck the switches on the ttops and doors and they seem to be ok. i  do notice that after i try and start it if I turn the key al the way to the off position tha the engine gives a little kick when the key is moved to the off pos. maybe ignition switch is bad or maybe out of adjustment? it is in such a wonderful place to get to I may have to ake the seat out to get down there on the floor and of coarse today  we are having freezing rain and wind chill at about 0. i was really hoping maybe something other than ign sw..

harry

Check the voltage at the dist first. That will give you an idea of whether or not the ign switch is werkin properly.
One thing I have run into is having correct voltages coming out of the switch itself, but not getting to the dist. Most of the time, the problem has been in the firewall pass-thru connector, under the brake booster, where the main engine harness "passes thru" to the fuse box. The terminals in there can get nasty/corroded over the years, and create all kinds of problems.
Believe it or not, that's usually the LAST place anyone looks!!!