Several weeks ago, I took my newly purchased 63 Valiant out for a drive and as I approached a stop sign the engine suddenly died. It cut off as fast as you could snap finger as opposed to slowing down to a halt. It restarted after a couple of seconds and rather than take a chance out on the highway of the same thing happening again I drove the car back home.

The engine has several modifications, on of which is an Edelbrock 4-bbl carb. It has a manual choke attached. As I initially looked over the motor, I saw that the choke cable had been improperly installed to the point where it failed to operate the chock mechanism smoothly. I had to replace the cable, install it correctly, and now it works fine.

Several days ago, I started the car without any problem, drove it around the neighborhood a little, and parked it.

Went out yesterday, started the car, and it died after about 10 seconds. Like the first instance, the engine just cut off. It would crank fine, but not fire.

On a whim (I know that isn't the way to do it) I purchased a new ECU (ignition includes Mopar electronic ignition system), cleaned up its mounting surface, installed it, and the car fired right up. I guess I was lucky.

How should I have diagnosed whether the engine died because of a faulty distributor, ballast resistor, coil or ECU instead of blindly possibly solving the problem by purchasing a new ECU?

ive defenitly just bought parts to throw at it if i didnt have time to dig into my DD on diagnosis. its pretty much hit or miss. but you knew to go with spark because of the quickness in dying vs a stuble. and all those old black magic boxes tend to freak out with heat...

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder

Pull a plug wire and hold the tip close to the valve cover while a friend cranks the motor. If you see no spark or a weak yellow spark then you have an ignition problem. The spark should be big and whitish blue.

If you don't have spark your first stop is to check the ballast resistor. If that checks out okay, then you check the coil. If that checks out then you check the ECU. Parts stores can usually test them for you.

oh, and to check to see if ballast is ok you would turn your key to the acc position and check positive side of coil for i think 7 ish volts under ballast. to check the trigger in the dizzy the best way is to backpin the connectors and check wit a labscope while crankin and check patern. as for the ecu you prety much check its power and grounds and see if its getting/making some input/output. and the coil you can either gap test it or do an ohm check of the windings which i think is less accurate cause its not under real conditions, like any ohm check

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder