Electronic ignition troubleshooting help

[Curt Chambers]

I'll pull the distributor if the no-start persists and look things over. It was installed into the engine shortly after getting the engine back from the rebuilder, who convienently left the engine at TDC for #1. That's why I'm pretty sure it's in correctly.

The single ballast resistor I'm currently using has .6 ohm resistance. I also have a dual laying around. It measures 1.4 ohm on the normal side and 5.2 on the aux side.

 

[RJRENTON]

Bob

I have never found an AFTERMARKET Jobber
Dual Ballast Resistor with the coil side at .5 Ohms

All the ones I tested are closer to 1.5 Ohms on the coil side

Now Ebay you might find a factory Mopar Dual Ballast like your talking about , but not cheap

Single Ballast Resistor is a different story - You can pretty much get any Ohm range you want

Scott

WHY would you want to NOT use the correct value ballast resistor? Especially when using a four (4) terminal ECU, a dual ballast resistor is not required. On the origional MOPAR ECU system, the dual ballast resistor was used as the value was 5.0 ohm that provided to power the ECU thru the 5th tetminal, while the 0.5 ohm was usef to provide power to coil and limit the current the ECU switched. Later the ECU was redesigned to eliminate the need for the 5.0 ohm dual ballast resistor and only use the 0.5 ohm resistor. Why are they're so many different values of ballast resistors??? Why do some people substitute different coils snd resistors in search of more horsepower or smoother operation, then have problems with the ECU failing prematurely? Cannot provide the answer....
BOB RENTON

 

[Bee1971]

"WHY would you want to NOT use the correct value ballast resistor?"



What the hell does the Ballast Resistor have anything to do with CRANKING VOLTAGE ?




Anyways did you know

1972 Dodge Charger left the factory with a DUAL BALLAST RESISTOR - Why would you want to change the factory wiring over to a Single Ballast Resistor ?

The 4 Pin ECU

It works fine with a DUAL BALLAST RESISTOR !

 

[LowBikeMike]

I'll pull the distributor if the no-start persists and look things over. It was installed into the engine shortly after getting the engine back from the rebuilder, who convienently left the engine at TDC for #1. That's why I'm pretty sure it's in correctly.

The single ballast resistor I'm currently using has .6 ohm resistance. I also have a dual laying around. It measures 1.4 ohm on the normal side and 5.2 on the aux side.

Are you sure the engine was TDC on #1 on the Compression stroke?

 

[RJRENTON]

I'm well aware of the differences between the 2 ballast resistor variations and the overall system operation.
Overall system resistance affects the voltage drop from the source point thru and including the coil primary. Perhaps the low voltages exhibited during cranking are a result of high or higher than normal overall resistances from the source point to the coil. IF, during cranking, the battery's terminal voltage drops too low due to sulfation, and the overall total resistance in the ignition circuit remains the same, the measured voltages will be lower, perhaps to the point of preventing adequate coil voltage from being developed and subsequently lower spark output. Again, Ohm's Law prevails.
BOB RENTON

 

[Curt Chambers]

Are you sure the engine was TDC on #1 on the Compression stroke?

Yes

 

[Curt Chambers]

I'm well aware of the differences between the 2 ballast resistor variations and the overall system operation.
Overall system resistance affects the voltage drop from the source point thru and including the coil primary. Perhaps the low voltages exhibited during cranking are a result of high or higher than normal overall resistances from the source point to the coil. IF, during cranking, the battery's terminal voltage drops too low due to sulfation, and the overall total resistance in the ignition circuit remains the same, the measured voltages will be lower, perhaps to the point of preventing adequate coil voltage from being developed and subsequently lower spark output. Again, Ohm's Law prevails.
BOB RENTON

So applying this to the test I just ran. With the ECU out of the circuit (disconnected), cranking voltage was more or less normal (10v). That should indicate that the ignition switch, bulkhead connector, and intervening wiring are probably OK. That's why I jumped the gun and ordered another ECU. Tomorrow I'll take some resistance measurements of the ECU harness (although that is new also).

 

[Bee1971]

I'm well aware of the differences between the 2 ballast resistor variations and the overall system operation.
Overall system resistance affects the voltage drop from the source point thru and including the coil primary. Perhaps the low voltages exhibited during cranking are a result of high or higher than normal overall resistances from the source point to the coil. IF, during cranking, the battery's terminal voltage drops too low due to sulfation, and the overall total resistance in the ignition circuit remains the same, the measured voltages will be lower, perhaps to the point of preventing adequate coil voltage from being developed and subsequently lower spark output. Again, Ohm's Law prevails.
BOB RENTON

He said battery voltage at the battery was fine during cranking from what I read

And

Exactly the reason I asked him to take a jumper wire from the positive side of the battery to the positive side of the coil during cranking or starting

And Post # 24 should answer the question about the distributor unless something just flat out broke internally

 

[RJRENTON]

So applying this to the test I just ran. With the ECU out of the circuit (disconnected), cranking voltage was more or less normal (10v). That should indicate that the ignition switch, bulkhead connector, and intervening wiring are probably OK. That's why I jumped the gun and ordered another ECU. Tomorrow I'll take some resistance measurements of the ECU harness (although that is new also).

Sure sounds like you're getting closer to the solution. I'd be curious as to your resistance readings and ultimately the results of the new ECU....which would be: everything is operating normally ...
BOB RENTON

 

[Curt Chambers]

Here are some wiring harness resistance measurements.

ECU Pin #1 to Ballast Resistor = .1 ohm
Pin #2 to Coil Neg = .1 ohm
Pin #3 n/a
Pin #4 to Distributor = .1 ohm
Pin #5 to Distributor = .1 ohm
Coil Pos to Ballast Resistor = .2 ohm
Coil primary winding Pos to Neg = 1.4 ohm
Distributor pickup coil = 283 ohm

New ECU should be here in a couple days.

 

[Don Frelier]

All this gets powered by the ignition through the firewall. Keep going back towards the source. Pull the bulkhead connection apart clean and inspect.

 

[HALIFAXHOPS]

WHY would you want to NOT use the correct value ballast resistor? Especially when using a four (4) terminal ECU, a dual ballast resistor is not required. On the origional MOPAR ECU system, the dual ballast resistor was used as the value was 5.0 ohm that provided to power the ECU thru the 5th tetminal, while the 0.5 ohm was usef to provide power to coil and limit the current the ECU switched. Later the ECU was redesigned to eliminate the need for the 5.0 ohm dual ballast resistor and only use the 0.5 ohm resistor. Why are they're so many different values of ballast resistors??? Why do some people substitute different coils snd resistors in search of more horsepower or smoother operation, then have problems with the ECU failing prematurely? Cannot provide the answer....
BOB RENTON

I prob can Bob there are different Ballast values for different MOPAR boxes. I have been actually testing boxes to see exactly when they fail and also doing different resistors. Definately afferct when the do or do not break up. Here is a quick ECU example.

 

[RJRENTON]

Thanx for the info re ECU, BALLAST RESISTOR combos and coils. The most important info is the last footnote on the PAGE.....DO NOT MIX AND MATCH COMPONENTS, in spite of what your next door's neighbor's brother in law's cousin's best friend's Uncle's sisters husband's says that it doesn't matter.....which amounts to a "they said" rule......
Typically, I've investigated the component failure on a few ECUs. Almost always the predominant failure has been the transistor on the outside of the case. This transistor is a Power Darlington design, which switches the coil's primary winding current off to generate the spark and then immediately back on to "charge" the coil's primary winding for the next spark. IF a lower ballast resistor value is used or a coil with low primary winding resistance too much current must be switched by Darlington transistor exceeding its current and tthermal limits. Additionally, if a coil with a higher inductive reactance is used, a higher than normal infuced voltage reflected back to the Darlington transistor possibly causing its premature failure....contrary to the "they said" rule. Just my opinion of course....
BOB RENTON

 

[Bee1971]

Not to sound like a smart *** but sounding like a smart ***

That Mopar Application Chart is AWESOME (Honestly) - If Direct Connection and Mopar Performance still existed today and made those same part numbers from the 70s 80s 90s

However its not 1980 anymore

Trying to find those American Made ECUs and Ballast Resistors and American Made Coils today as New Old Stock is like finding , and putting that same package together in that chart today GOOD LUCK

So with that said


HOW DO YOU MATCH UP TODAYS CHINESE MEXICAN ECUs AND CHINESE MEXICAN BALLAST RESISTORS AND CHINESE MEXICAN COILS And put a complete working package together when 90% of todays ECUs are running fake TRANSISTORS ? Todays crap is just that in spite of what your next door's neighbor's brother in law's cousin's best friend's Uncle's sisters husband's says that it doesn't matter.....which amounts to a "they said" rule......


Bob i will bee waiting for your answer

 

[HALIFAXHOPS]

I am lucky since I deal with distributors all the time. your best bet is look for old NORS or Mopar built before 1980 or so. The fake transistor is easy to see it is sometimes taller and all of the fake ones have no part number stamped on them. Todays parts store parts are a serious crap shoot on what you will get. I bet not many still test them either. We beat it up hard in here n the ECU's. You ever need one or have one tested I have a few Zetron tester like they used to use in the parts stores.

1974 Brain Box saves the day. | For A Bodies Only Mopar Forum

 

[Curt Chambers]

What about points? When I purchased this car it had a points distributor and coil in it. I removed them because I wanted to go back to the correct factory setup. If I don't have success after the next ECU, maybe I should just reinstall those and see what happens? I know electronic ignition is supposed to be more reliable, but maybe that's not true anymore with these cars. Just a thought.

 

[RJRENTON]

Not to sound like a smart *** but sounding like a smart ***

That Mopar Application Chart is AWESOME (Honestly) - If Direct Connection and Mopar Performance still existed today and made those same part numbers from the 70s 80s 90s

However its not 1980 anymore

Trying to find those American Made ECUs and Ballast Resistors and American Made Coils today as New Old Stock is like finding , and putting that same package together in that chart today GOOD LUCK

So with that said


HOW DO YOU MATCH UP TODAYS CHINESE MEXICAN ECUs AND CHINESE MEXICAN BALLAST RESISTORS AND CHINESE MEXICAN COILS And put a complete working package together when 90% of todays ECUs are running fake TRANSISTORS ? Todays crap is just that in spite of what your next door's neighbor's brother in law's cousin's best friend's Uncle's sisters husband's says that it doesn't matter.....which amounts to a "they said" rule......


Bob i will bee waiting for your answer

VERY TRUE.....its a crap shoot as to the reliability of the present available parts, regardless of their origin. The only, and perhaps the best way to determine compatibility, is to measure the resistance of the ballast resistor and the coil's primary winding resistance to see if they exceed a maximum value b4 purchase. But....what's the maximum not to exceed value? Difficult to determine. As Halifax Hops noted, the external transistor is likely to be a "fake" device. But what does the coil's current switching if this transistor is not real? Very possible an IGBT device is used. (I=insulated, G=gate, B=bi-polar, T=transistor) which, when applied, within design parameters, will function satisfactorily for a stated time period. IGBT devices react faster and are more immune to switching transients, like those generated by miss matched components, but still need to be applied to not to exceed certain design parameters. But how many users have the test equipment or knowledge of the how and why? Most users seek a reliable and cost effective solutions to a real or perceived problem or maybe some just yield to peer pressure. Some of us (me) seek origionality in appearance and operation; others seek greater (?) or better operation, real or perceived.
What's the solution? Go back to points/condensers or a totally computerized vehicle operation....EFI + sensors with O2 trim, etc......the choice is up to the individual or his/her check book. Just my opinion of course.
BTW.....What's your solution or recommendation?
BOB RENTON

 

[Bee1971]

I prob can Bob there are different Ballast values for different MOPAR boxes. I have been actually testing boxes to see exactly when they fail and also doing different resistors. Definately afferct when the do or do not break up. Here is a quick ECU example.
View attachment 1067890

Would bee interested in your results

My ECU Dilemma

I can honestly say I don’t remember any of these ECUs actually failing or leaving me on the side of the road as in a no start situation

However , coils on the other hand

Anyways in numerous threads over the last couple years , I was chasing my *** on intermittent RPM issues anywhere as low as 4,000 to 5,000 - 5,200 RPMs etc.

I chased so I thought fuel issues , wiring , plug / wires blah blah blah even a few distributors , worn bushings

I even went as far as taping a fuel pressure gauge to my windshield while running the car on the road

I literally tried four or five different working or new ECUs , all different Chinese manufactures after my reliable Mopar Chrome box that was on my car for over twenty years started acting up around the same time I built my 500 HP little 432 Stroker

That Mopar Chrome box started all my ECU issues and everything after that was honestly a crap shoot

Different coils , different OHM rating ballast resistors based on those coils

I didn’t or wasn’t ready for a MSD Ignition Box and or system just yet

So I went back to basics , my factory original points distributor and just a standard uc coil and 1.5 OHM Ballast

Well at least that confirmed my ignition issues above 5,000 RPMs - Damn motor was pulling to 6,000 RPMs all day long - I am not saying it was making much power at that RPM , but it wasn’t missing or feeling like it was dropping cylinders

So I went back to the electronic ignition and the search was on for a reliable box and complete system

Well I found two of these just by chance - Made in the USA new old Standard LX101 in original boxes never mounted

1986 and 1987 Vintage on the boxes and Transistors

 

[Bee1971]

VERY TRUE.....its a crap shoot as to the reliability of the present available parts, regardless of their origin. The only, and perhaps the best way to determine compatibility, is to measure the resistance of the ballast resistor and the coil's primary winding resistance to see if they exceed a maximum value b4 purchase. But....what's the maximum not to exceed value? Difficult to determine. As Halifax Hops noted, the external transistor is likely to be a "fake" device. But what does the coil's current switching if this transistor is not real? Very possible an IGBT device is used. (I=insulated, G=gate, B=bi-polar, T=transistor) which, when applied, within design parameters, will function satisfactorily for a stated time period. IGBT devices react faster and are more immune to switching transients, like those generated by miss matched components, but still need to be applied to not to exceed certain design parameters. But how many users have the test equipment or knowledge of the how and why? Most users seek a reliable and cost effective solutions to a real or perceived problem or maybe some just yield to peer pressure. Some of us (me) seek origionality in appearance and operation; others seek greater (?) or better operation, real or perceived.
What's the solution? Go back to points/condensers or a totally computerized vehicle operation....EFI + sensors with O2 trim, etc......the choice is up to the individual or his/her check book. Just my opinion of course.
BTW.....What's your solution or recommendation?
BOB RENTON

Trying to find Made In The USA New Old Stock ECUs

Mopar Performance ECUs from the 80s and 90s at swap meets or online

I found this brand new on EBay this past winter for $35.00

 

[RJRENTON]

I am lucky since I deal with distributors all the time. your best bet is look for old NORS or Mopar built before 1980 or so. The fake transistor is easy to see it is sometimes taller and all of the fake ones have no part number stamped on them. Todays parts store parts are a serious crap shoot on what you will get. I bet not many still test them either. We beat it up hard in here n the ECU's. You ever need one or have one tested I have a few Zetron tester like they used to use in the parts stores.

1974 Brain Box saves the day. | For A Bodies Only Mopar Forum

VERY INTERESTING WRITE UP...
The last pic in the article shows the innards b4 the potting compound and something that appesrs to be a large wirewound resistor and a internally mounted transistor or zener diode on a heat sink that reduced the voltage of the externally mounted 5.0 ohm resistor (part of the 5.0 ohm/0.5 ohm dual ballast resistor) to operate the module's circuit. These components were eliminated in later revisions of the module to eliminate the 5th pin connection and to "enhance" the operation and increase reliability.
BOB RENTON