Hello Bob, good to hear from you. I have the RB. And have that on order as a back up.
Issue I’m having is engine fires up cold no problem, but this summer I have had there occasions when out for a hot New England summer evening cruise the engine will cut out without so much as a sputter. Engine temp gauge is good, usually under 180. Have plenty of juice at the battery trying to start again. Check for fuel at the carb but no start. Thought I fixed it the second time by replacing the ECU on the roadside and the engine fired right up. Ground is good at the ECU. Looked over the wiring for scuns, breaks or loose connections.
Watched a YouTube video by Scannerdanner, found it quite helpful For troubleshooting the electronic ignition. From now on I’m bringing a test light and a multi meter in hopes of pinning down the problem, just want to know what voltages to see at the ballast and coil. Scannerdanner has 4.5 at the coil plus and 1.5 at coil negative, where I have double that, 9.2 at coil plus and 4 at coil negative. Is it possible to have too much current to overheat the coil or ECU? Has me wondering if ignition cools down enough during shutdown then it starts up? Your insight is very much appreciated.
John
John,
Thank you for your compliment.....the original, Mopar electronic ignition system is/was quite simple.
For argumentative explanation, assume the 2 nd generation system using a single ballast resistor of approximately 0.5 ohms and the orange box ECU. The 0.5 ohm ballast resistor limited the coils primary current (except when in the start mode, when the coil receives full battery voltage to provide easier starting) and to limit the current the ECU switching transistor handles.
The ECU transistor is ON all the time and the pickup coil and reluctor in the distributor, produces a pulse, one for each cylinder, which turns OFF the switching transistor creating the spark. The "dwell time" or coil recharge time is measured by the ECU's circuitry to turn on the coil for recharge immediately after the spark has occurs.
As a side bar, the 1st generation system used a dual section ballast resistor comprised of 0.5 ohms and 5.0 ohms. The 5.0 ohms section powered the electronics of the ECU while the 0.5 ohm section limited coil. The balance of the circuit operates as noted previously.
What is the cause of your problem? Try not to be confused by your various voltage readings. Assuming we're in the ignition tun mode, the basic circuit is simple: 12 volts to the ballast resistor. Depending on the coil's primary winding resistance and resistance of the ballast resistor, thru the ECU to ground, ix the ECU securely grounded and the various connections, absolute readings are approximate. What is your coil's primary winding resistance? What is the value of the ballast resistor? Which generation of ECU are you using. Using Ohms law (E = I x R) and Kirchhoff's circuit laws (the algebraic sum of all the currents in any given circuit will be equal to zero).
Component mis-matching....is often the problem.....the "my buddy says rule" is often to blame. CHINESE manufactured components due to poor QC or shabby materials is often blamed. Coil are temperature sensitive if not of adequate insulation design.....they can develop internal shorts or low resistance to ground due to heat. Have you tried an EPOXY FILLED coil? Almost impervious to heat and vibration. But it is IMPERATIVE that the components must COMPLIMENT each other and not exceed their respective maximums. Without knowing your exact components individual resistance during a no start condition, it's difficult to make an exact determination of the fault. ....not sure if I've answered your question....let me know if I can help more.....
BOB RENTON
