Chasing Ignition Problem

[EngineerDoug]

Hello all,

It's yet another electronic ignition question! I've got a new motor running on the Mopar electronic ignition system - all new coil, ballast, ignition box, distributor, and plug wires.

I am fiddling with it to get it running right and probably have more than one issue going on. Note I am still tuning the six pack setup, so the fuel part of the equation may be a bit "off" yet.

So after I drive it around a bit, it starts to run more ragged. Once I stopped I could not get it restarted. Seemed like ignition, so I started troubleshooting the components listed above. Swapped out the control box & ballast but no joy. Securely grounded the ignition box, too. I did find that the reluctor gap in the distributor was too wide (0.014"). Would that be wide enough to cause problems? I know the spec is 0.008".

Out of curiosity I tried an experiment - connected my timing light and cranked the engine. I expected to see the light flash while the engine was cranking, but saw nothing. I get spark from the coil, however. Wouldn't you expect to see the timing light flash? I know I need to pull a plug and check for spark at the cylinder, but shouldn't the timing light be triggered during cranking?

Also, I know my charging system is OK, as it puts out 14.0V. I did connect the car to a battery charger to facilitate these experiments and saw that it puts out at least 16V. Could this be enough to damage the ignition box?

I know these are oddball questions, but I just want to eliminate unknowns or possible clues.

Thanks.

 

[66Satellite47]

My bet is the control box is not properly grounded. The mounting screws alone may not provide a good ground.

 

[RJRENTON]

Hello all,

It's yet another electronic ignition question! I've got a new motor running on the Mopar electronic ignition system - all new coil, ballast, ignition box, distributor, and plug wires.

I am fiddling with it to get it running right and probably have more than one issue going on. Note I am still tuning the six pack setup, so the fuel part of the equation may be a bit "off" yet.

So after I drive it around a bit, it starts to run more ragged. Once I stopped I could not get it restarted. Seemed like ignition, so I started troubleshooting the components listed above. Swapped out the control box & ballast but no joy. Securely grounded the ignition box, too. I did find that the reluctor gap in the distributor was too wide (0.014"). Would that be wide enough to cause problems? I know the spec is 0.008".

Out of curiosity I tried an experiment - connected my timing light and cranked the engine. I expected to see the light flash while the engine was cranking, but saw nothing. I get spark from the coil, however. Wouldn't you expect to see the timing light flash? I know I need to pull a plug and check for spark at the cylinder, but shouldn't the timing light be triggered during cranking?

Also, I know my charging system is OK, as it puts out 14.0V. I did connect the car to a battery charger to facilitate these experiments and saw that it puts out at least 16V. Could this be enough to damage the ignition box?

I know these are oddball questions, but I just want to eliminate unknowns or possible clues.

Thanks.

IMO....

Its possible that the coil is breaking down due to heat; is it the coil recommended or some other aftermarket coil? I would also consider the ballast resistor....is it the one furnished/recommended. The coil and ballast resistor should be coordinated components. A few tenths of voltage difference should not damage the control box or affect its operation. Re-adjudt the reluctor gap to specs....0.008". Check coil wire to distributor for continuity...is rotor OK? Just a few additional thoughts....
BOB RENTON

 

[davek]

check your coil,just had mine act up and did everything you did and the coil was the last thing I checked. I had a bad coil.

 

[moparedtn]

Ballast or coil...

 

[EngineerDoug]

OK thanks for the replies. This morning it started up no problem and seems to be running better. I still need to put some miles on it but so far so good. The ground on the ECU was good - I even had an additional ground lug + wire running from the ECU case to the engine ground. Appears the reluctor gap + high float levels might account for some/all of the issue. I will keep an eye on the coil, however. It is an Accel Super Stock coil with 1.5 ohms advertised internal resistance, and the ballast is the one that came with the ignition kit.

 

[RJRENTON]

OK thanks for the replies. This morning it started up no problem and seems to be running better. I still need to put some miles on it but so far so good. The ground on the ECU was good - I even had an additional ground lug + wire running from the ECU case to the engine ground. Appears the reluctor gap + high float levels might account for some/all of the issue. I will keep an eye on the coil, however. It is an Accel Super Stock coil with 1.5 ohms advertised internal resistance, and the ballast is the one that came with the ignition kit.

FYI....
Just be aware that the TRANSISTOR on the outside of the ECU's case, must switch the coil's primary winding current, limited to the resistance provided by the ballast resistor ohmic value AND the inductive reactance of the coil. IF the coil's primary winding current, and the INDUCED PRIMARY VOLTAGE (which occurs when spark occurs becsuse of its reactance) exceeds the transistor's capabilities, the POSSIBILITY of damage to the ECU can occur. This is contrary to what your next door's neighbor's brother in law's cousin's best friend's sister-in-law husband's nephew may say. Why not use the Mopar coil designed for the system?..... just my opinion of course.
BOB RENTON

 

[EngineerDoug]

Got another question on this issue, as I wonder about the state of my wiring/ignition switch. Does anybody have a ballpark figure for what voltage drop (or resistance) to expect from the battery positive terminal to the ballast resistor when the key is in the "run" position? Original 52 year old ignition switch.....

 

[1toolguy]

ake sure you are using a low-impedance (0.8-1.2 ohms primary resistance) coil specifically for Mopar electronic ignitions. If it's an off the shelf "universal" (aka Chevy) coil it'll have too much resistance which will overheat the ignition box and shut it down. Hopefully the ignition box wasn't damaged.

 

[RJRENTON]

ake sure you are using a low-impedance (0.8-1.2 ohms primary resistance) coil specifically for Mopar electronic ignitions. If it's an off the shelf "universal" (aka Chevy) coil it'll have too much resistance which will overheat the ignition box and shut it down. Hopefully the ignition box wasn't damaged.

As I noted previously, the Mopar specific coil and ballast resistor should be coordinated to not exceed the switching transistor's on the outside of the case of the ECU capacity. Failure to do so usually results in a failure of the ECU. After market ECU's of foreign origin, may contain underrated components, especially the Power Darlington transistor (that switches or makes and breaks the coil's primary current flow) CAN be damaged if its operating parameters are exceeded, usually brought on by incorrectly mix-matching parts. Just my opinion of course.
BOB RENTON

 

[Don Frelier]

ake sure you are using a low-impedance (0.8-1.2 ohms primary resistance) coil specifically for Mopar electronic ignitions. If it's an off the shelf "universal" (aka Chevy) coil it'll have too much resistance which will overheat the ignition box and shut it down. Hopefully the ignition box wasn't damaged.

I would expect too little resistance to cause problems?
I=V/R

 

[RJRENTON]

I would expect too little resistance to cause problems?
I=V/R

According to Ohm's Law, one would assume YES....BUT... if, resistance approaches zero (0) ohms, then current (I) would approach infinity, limited to the inductive reactance of coil's primary winding and the current capacity of the switching transistor. As in GM's HEI system, the coil's primary winding resistance and inductive reactance and the switching transistor's current and voltage handling capabilities compliment each other, by design, not by the often used, "trial and error" method used by some subscribers. Just my opinion of course.
BOB RENTON