My cuda will start but wont run
07-29-2011, 07:51 PM
#1
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My cuda will start but wont run
Ok ill try to keep this simple. The car is a 1968 barracuda with a 383 conversion the car is in rough condition as in it needs a complete restoration. The engine is a 1969 383bb and used to run strong until I decided to buy a new coil for it because the one that was on it looked like it was from 1969. The problem is that after I installed the new msd coil in the autozone parking lot I drove it back to my place and turned the car off. I tried to turn the car back on a few minutes later and it will now only run for a few seconds when I have the key in the start position. The minute I let go of the key the car instantly dies.
I tried everything from swapping the wires on the coil(I thought maybe the car had been wired wrong like a car I used to have)to exchanging the new coil for another new one and then when that didnt work I put the old coil back on and I am still having the same problem. The distributor is not electric and has not been touched or moved. One of you mopar car gods please help the retarded beginner with this im tired of looking like an idiot for not being able to fix this.
I tried everything from swapping the wires on the coil(I thought maybe the car had been wired wrong like a car I used to have)to exchanging the new coil for another new one and then when that didnt work I put the old coil back on and I am still having the same problem. The distributor is not electric and has not been touched or moved. One of you mopar car gods please help the retarded beginner with this im tired of looking like an idiot for not being able to fix this.
07-29-2011, 10:43 PM
#4
Mopar Lover
I agree with 340 thats its a ballast resister. Confirm it with a test light or voltmeter. Turn the key to the run position. If you have power to one side of the ballst resister and not the other, the resister is bad.
07-30-2011, 03:30 AM
#5
Mopar Lover
You must match the coil to your mopar ignition system. the MSD coil might have "cooked the ballast due to a difference in the ohm reading of the coil. Id try a coil that is MADE for a mopar ignition systen. TRy NAPA and get a proper ciol made for a mopar ignition. I am not sure what is required to use the MSD coil with a mopar ignition system. I do know that too much voltage will fry the mopar ignition box. That is the reason for the ballast resistor. It is used with the old points system AND the Mopar elecronic ignition system.
07-30-2011, 10:42 AM
#6
Sounds like ballast. You need to realize just how Mopar ignition systems work You have three separate wires on separate circuits from the ignition switch.
When you twist the key to "start" TWO of the circuits are hot, the yellow start wire which engages the start relay, and it engages the starter
The brown "ignition bypass" wire goes to the coil side of the ballast, and is in fact what is running your engine while the key is in "start."
When you RELEASE the key, the brown wire goes COLD and the BLUE "run" circuit is then hot. It goes THROUGH the ballast. If the ballast fails, the symptom you have now is the result.
EASY to troubleshoot:
Take a meter or test lamp turn the key to "run" and check both sides of the ballast. A good ballast will have 12V or a "bright" bulb on the "dark blue" side, and a lot less voltage, or "dim" test lamp on the coil side
IF you have a bright bulb on one side, obviously you are getting voltage from the ignition switch.
When you twist the key to "start" TWO of the circuits are hot, the yellow start wire which engages the start relay, and it engages the starter
The brown "ignition bypass" wire goes to the coil side of the ballast, and is in fact what is running your engine while the key is in "start."
When you RELEASE the key, the brown wire goes COLD and the BLUE "run" circuit is then hot. It goes THROUGH the ballast. If the ballast fails, the symptom you have now is the result.
EASY to troubleshoot:
Take a meter or test lamp turn the key to "run" and check both sides of the ballast. A good ballast will have 12V or a "bright" bulb on the "dark blue" side, and a lot less voltage, or "dim" test lamp on the coil side
IF you have a bright bulb on one side, obviously you are getting voltage from the ignition switch.
07-30-2011, 12:45 PM
#7
Mopar Lover
I though in a points type ignition the ballast resistor get bypassed during cranking so the coil gets full voltage..?
That's what i had always thought...
That's what i had always thought...
Last edited by blue 68 gts; 07-30-2011 at 01:06 PM.
07-30-2011, 01:01 PM
#8
Mopar Lover
07-30-2011, 02:06 PM
#9
THIS POST you linked to was POSTED BY ME!!!!!
And now, for the CORRECT answer. Ballasts change resistance with current as they heat and cool, and thus provide a sort of buffer for the coil. Coil current will be different at higher and lower RPM.
But the REAL nitty gritty reason is "easier starting."
A normal system runs close to 14V, and Mopar coils used to run anywhere from 8-10V AT THE COIL at the bottom end of the ballast.
When you crank the engine for start, the switch bypasses the resistor, so the coil STILL GETS about 10V--so a nice hot spark for starting.
This is something the ol' 6V cars never had.
Thats the best answer. The ballast reduces the current flow thru the coil at low speeds and keeps the coil from overheating. As was said the coil can handle more amperage but not for long periods of time. So at idle and low eng speeds the points have more time to be closed and thus the current heats the ballast up and causes it to have more resistance and drop current flow at lower eng speeds when full coil output is not needed. When you go faster and speed the eng up the points have less time to be closed so the ballast cools down some and the resistance drops causes more current to flow thru the coil and letting the coil output higher when it is needed at higher eng speeds. And when cranking the ign system needs full output to help start the eng so the ign switch bypases the ballast and gives full battery volts to the coil while cranking. Ron
07-30-2011, 05:24 PM
#10
Mopar Lover
I JUST got through explaining this. Re-read my post. HINT: brown wire
THIS POST you linked to was POSTED BY ME!!!!!
And now, for the CORRECT answer. Ballasts change resistance with current as they heat and cool, and thus provide a sort of buffer for the coil. Coil current will be different at higher and lower RPM.
But the REAL nitty gritty reason is "easier starting."
A normal system runs close to 14V, and Mopar coils used to run anywhere from 8-10V AT THE COIL at the bottom end of the ballast.
When you crank the engine for start, the switch bypasses the resistor, so the coil STILL GETS about 10V--so a nice hot spark for starting.
This is something the ol' 6V cars never had.
Thats the best answer. The ballast reduces the current flow thru the coil at low speeds and keeps the coil from overheating. As was said the coil can handle more amperage but not for long periods of time. So at idle and low eng speeds the points have more time to be closed and thus the current heats the ballast up and causes it to have more resistance and drop current flow at lower eng speeds when full coil output is not needed. When you go faster and speed the eng up the points have less time to be closed so the ballast cools down some and the resistance drops causes more current to flow thru the coil and letting the coil output higher when it is needed at higher eng speeds. And when cranking the ign system needs full output to help start the eng so the ign switch bypases the ballast and gives full battery volts to the coil while cranking. Ron
THIS POST you linked to was POSTED BY ME!!!!!
And now, for the CORRECT answer. Ballasts change resistance with current as they heat and cool, and thus provide a sort of buffer for the coil. Coil current will be different at higher and lower RPM.
But the REAL nitty gritty reason is "easier starting."
A normal system runs close to 14V, and Mopar coils used to run anywhere from 8-10V AT THE COIL at the bottom end of the ballast.
When you crank the engine for start, the switch bypasses the resistor, so the coil STILL GETS about 10V--so a nice hot spark for starting.
This is something the ol' 6V cars never had.
Thats the best answer. The ballast reduces the current flow thru the coil at low speeds and keeps the coil from overheating. As was said the coil can handle more amperage but not for long periods of time. So at idle and low eng speeds the points have more time to be closed and thus the current heats the ballast up and causes it to have more resistance and drop current flow at lower eng speeds when full coil output is not needed. When you go faster and speed the eng up the points have less time to be closed so the ballast cools down some and the resistance drops causes more current to flow thru the coil and letting the coil output higher when it is needed at higher eng speeds. And when cranking the ign system needs full output to help start the eng so the ign switch bypases the ballast and gives full battery volts to the coil while cranking. Ron
Ok. Makes more sense to me and is clearer. Thank you.
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