- - Bug in ignition system
(http://www.clubcobra.com/forums/ignition/112862-bug-ignition-system.html)
BlueRooster
10-09-2011 10:43 AM
Bug in ignition system
The motor cranks over fine. The motor will start with the key pegged to the right, but as soon as I let the key off from crank to run it dies. There is spark during crank, but no spark during run.
There are other things that happened before this issue, but I am wondering if I am overlooking something simple before I go into more detail. I just want to see what you guys thought first.
BTW: SPF, 460, carb.
Grubby
10-09-2011 12:35 PM
I would jumper a wire form B+ to the coil. Then try to start it. If it stays running it is the ignition switch.
John
BlueRooster
10-09-2011 01:39 PM
OK. I already switched the ignition switch and the same exact behavior happens. I will run a wire from the positive on the battery to the coil and see how it goes thanks.
patrickt
10-09-2011 05:01 PM
Quote:
Originally Posted by BlueRooster
(Post 1155435)
The motor cranks over fine. The motor will start with the key pegged to the right, but as soon as I let the key off from crank to run it dies.
That's usually the classic symptoms of a bad ballast resistor circuit. When you're cranking, the solenoid bypasses the ballast resistor, but as soon as you let go of the key, the solenoid is no longer energized and the current to the coil is through the ballast resistor instead. If there's a short in that circuit (like a bad ballast resistor) you get no spark.
BlueRooster
10-09-2011 06:02 PM
Thanks Patrick. That's a good direction to go in. Now, where is this little bastard.
patrickt
10-09-2011 06:14 PM
Quote:
Originally Posted by BlueRooster
(Post 1155477)
Thanks Patrick. That's a good direction to go in. Now, where is this little bastard.
It's usually over on a footbox/fenderwell area, but it really could be anywhere in the coil wiring circuit. Here's a little vid on testing it:
patrickt
10-09-2011 06:19 PM
Obviously if you get NO VOLTAGE on that test, then you have a ballast resistor and it is faulty.
BlueRooster
10-10-2011 05:43 AM
Great video Patrick! I now have a quick Columbus day project.
patrickt
10-10-2011 08:17 AM
Quote:
Originally Posted by BlueRooster
(Post 1155556)
Great video Patrick! I now have a quick Columbus day project.
Let me also add that if you have a MSD Ignition, or the like, that the test DOES NOT APPLY and that you will not have 12V power (or less) on the plus side of the coil. The reason 12V won’t be there is that a capacitive discharge ignition uses a big-ass capacitor to discharge several hundred volts to the coil. Some electronic ignitions do use a ballast resistor, so you really have to tell us what's under there, along with what your readings are on the volt meter. But if you do have a plain vanilla, stock inductive ignition, and you have no voltage at the coil, then you've found your problem.
mreid
10-10-2011 08:33 AM
The easiest way to tell is to look at the starter solenoid. If there is a wire on the "I" terminal (small terminal with small gauge wire on the right), then there is a very good chance you have the ballast resistor. If you disconnect this wire and the car doesn't start at all, then you know the ballast circuit is faulty (either wiring or the the resistor).
patrickt
10-10-2011 08:41 AM
Quote:
Originally Posted by mreid
(Post 1155586)
The easiest way to tell is to look at the starter solenoid. If there is a wire on the "I" terminal (small terminal with small gauge wire on the right), then there is a very good chance you have the ballast resistor. If you disconnect this wire and the car doesn't start at all, then you know the ballast circuit is faulty (either wiring or the the resistor).
Mreid is talking about this guy right here. This is a pic of my starter solenoid. I do not have a ballast resistor, and pulling that wire does nothing on my car. The ERA wiring harness just comes with it (in case you need it) so it gets hooked up to the solenoid whether you have a ballast resistor or not.
Since ballast resistors are 3 dollars I decided to buy one. I found the ballast next to the fuse box. I swapped it without the coil/ballast test. The car starts and runs perfectly.
Note to self: Don't jump start the Cobra again.
Thank again to Patrick and Mreid.
patrickt
10-10-2011 04:20 PM
Quote:
Originally Posted by BlueRooster
(Post 1155664)
Since ballast resistors are 3 dollars I decided to buy one. I found the ballast next to the fuse box. I swapped it without the coil/ballast test. The car starts and runs perfectly.
Hurray! I love it when we get it right the first time, which we do only about half the time.:LOL:
