Electronic ignition troubleshooting help

[RJRENTON]

The ballast resistor limits the current that the ECU/MODULE must switch. The module turns OFF the coil's primary current to produce the spark then IMMEDIATELY turns ON the coil's primary current or dwell time for the next spark, limited to the amount the value of the ballast resistor allows. During cranking, the ballast resistor is bypassed allowing full voltage and current to the coil, to produce the spark. The pickup coil in the distributor furnishes the WHEN, the spark is to occur, the ECU, simply does the on/off switching.
Are you sure the distributor is in the correct orientation with respect to the firing order. The distributor rotates COUNTER CLOCKWISE and the firing order is: 1-8-4-3-6-5-7-2 with the.even numbered cylinders on the passenger's side and the odd numbered cylinders on the driver's side.
It sounds like to me that POSSIBLY the wires are orientated incorrectly. DO YOU HAVE A FACTORY SHOP MANUAL, as it explains the correct distributor and plug wire orientation, to review your installation?
Just my opinion of course.....
BOB RENTON

 

[Bee1971]

Factory set up

 

[Bee1971]

Like Bob said , the ballast resistor is bypassed in the starter cranking of using your ignition key

Supplying full battery voltage to the positive side of coil

I wanted you using a jumper wire thinking maybe you had a wiring harness issue

Obviously not the case

 

[Curt Chambers]

The distributor and firing order are correct. Remember, a couple weeks ago it started and ran fine with this setup. Nothing was changed. I came out 2 days later and it wouldn't start. See post #24.

 

[Bee1971]

Post 24 - New ECU fired right up

Post 25 - Won’t start but has spark and tried starting fluid also

Post 27 - Has great spark at tower but still no start

Now

Post 28 - You had a serious voltage / amp draw and everything went to hell after that


Time to start looking at your bulkhead connectors

Alternator draw

Voltage regulator draw

Think Think Think

New starter
Battery is good

ECU and or ground - Pick up coil in distributor

Talking out loud to myself

 

[Curt Chambers]

The "great spark" referred to in Post #27 was in fact yellow. At the time I didn't know yellow was bad. It was certainly better than the no spark I was getting prior to replacing the ECU.

The voltage drop detected in Post #28 was probably there all along. It wasn't until the second no-start incident that someone asked for the cranking voltage. Up until then it was assumed the ECU was bad since it wasn't getting any spark.

It's certainly possible that all the dry cranking has caused other problems, or damaged other components. But I don't know how to check alternator draw or voltage regulator draw (both of which are new, btw). And I have no idea how to check the pickup coil, either. I assume you just buy a new distributor.

I do appreciate the help and suggestions. I really do. But I think I'm in over my head. At this point the solution is either a trustworthy mechanic or Craigslist.

 

[RJRENTON]

FYI.....Rick Ehrenberg's email.... [email protected]
Regarding your questions about the "alternator draw" and "voltage regulator draw", if defective, neither one would cause a "no start" condition. If defective, the voltage regulator will cause a no charge or over change condition and a defective alternator will exhibit the same no charge or low charge condition. The distributor pickup coil can be checked for continuity (resistance between disconnected plug terminals....approximately 500 ohms +/-) or to ground which would be infinity....no resistance to ground......possibility but not likely. NO...the pickup coil assembly can be replaced but the reluctor must be removed first plus 2 external screws. Insure the ECU IS GROUNDED....the coil circuit goes thru the ECU's ground connections....without an adequate ground connection, intermittent operation will result.
Go back and review #62 suggestions.....very helpful....
BOB RENTON

 

[Bee1971]

I agree on the ground , I also mentioned that

Anyways

Curious
Just disconnect the ECU wiring harness from the ECU and leave it hanging

Then crank over the engine and let me know your voltage drops , what your voltage is at the positive side of the coil and ballast resistor versus when your ECU is connected to the wiring harness in series

Want to know how much that Chinese ECU is drawing in voltage connected versus disconnected

 

[RJRENTON]

I agree on the ground , I also mentioned that

Anyways

Curious
Just disconnect the ECU wiring harness from the ECU and leave it hanging

Then crank over the engine and let me know your voltage drops , what your voltage is at the positive side of the coil and ballast resistor versus when your ECU is connected to the wiring harness in series

Want to know how much that Chinese ECU is drawing in voltage connected versus disconnected

IF YOU'VE disconnected the ECU, there will be an open circuit for the coil. The coil's primary winding current path is from the ballast resistor thru the coil to the ECUs transistor to the case to ground. Because there is no resistance, there will be no appreciated measured voltage drop....the coil's supply connection should read 12 volts for both ignition on and cranking conditions....because there is no current flow....
BOB RENTON

 

[Bee1971]

He is losing 4 to 5 volts in the cranking position at the positive side of the coil



What is drawing that energy then ?

Has to bee something

 

[Curt Chambers]

I'll do this test tomorrow. Disconnect the ECU and do a cranking voltage test at the Coil + terminal. If I'm understanding this test correctly, normal voltage would indicate a problem in the ECU or ECU ground. Continued reduced voltage would indicate a problem somewhere else in the ignition circuit. Is that correct?

 

[Bee1971]

Yes like mentioned you should have full battery voltage when disconnected



I know a lot of these things Bob mentioned

When you pull your ECU wiring harness look at the plug pins

Then run a separate ground wire from the ECU mounting bolt to the negative side of the battery or a known good ground to just confirm

You verified .008 air gap on the reluctor / pickup inside distributor

And you unclipped ignition bulkhead connector looking for corrosion / resistance

And these Chinese ECUs will fail fast and furious , not what you want to hear

 

[RJRENTON]

Yes like mentioned you should have full battery voltage when disconnected



I know a lot of these things Bob mentioned

When you pull your ECU wiring harness look at the plug pins

Then run a separate ground wire from the ECU mounting bolt to the negative side of the battery or a known good ground to just confirm

You verified .008 air gap on the reluctor / pickup inside distributor

And you unclipped ignition bulkhead connector looking for corrosion / resistance

And these Chinese ECUs will fail fast and furious , not what you want to hear

Another point to ponder is the IGNITION SWITCH. The switch's intetnal contacts MAY be failing or the connections to the switch as well. As it has been pointed out many times by others about the bulkhead connections, the same holds true with regard to the switch connections both internal to the switch and the wires connecting to the switch.
Years ago, a colleague had an intermittent start/no start condition AND a run/stop condition with his 1970 Chrysler 300 Hurst.....after much head scratching, we pulled the steering wheel and lock plate mechanism to find burned and severely corroded switch contacts. The fix was to replace the entire switch and the damaged connecting wires. BE ADVISED, if you go in this direction, the ignition switch/steering column is extremely compact assembly with limited accessibility .... but ... your voltage drop issues MAY lie with the ignition switch assembly. Just my opinion of course.
BOB RENTON

 

[64fury74charger]

Another point to ponder is the IGNITION SWITCH. The switch's intetnal contacts MAY be failing or the connections to the switch as well. As it has been pointed out many times by others about the bulkhead connections, the same holds true with regard to the switch connections both internal to the switch and the wires connecting to the switch.
Years ago, a colleague had an intermittent start/no start condition AND a run/stop condition with his 1970 Chrysler 300 Hurst.....after much head scratching, we pulled the steering wheel and lock plate mechanism to find burned and severely corroded switch contacts. The fix was to replace the entire switch and the damaged connecting wires. BE ADVISED, if you go in this direction, the ignition switch/steering column is extremely compact assembly with limited accessibility .... but ... your voltage drop issues MAY lie with the ignition switch assembly. Just my opinion of course.
BOB RENTON

I have been plagued by this very issue on my 74 Charger, Replaced ignition switch, t/s switch, etc etc. Still have issues that lead there. I eliminated all the ignition problems under the hood with MSD and boy what a tremendous difference. But I am not concerned with stock parts, just reliable parts. I tried an assortment of ecu and distributors that were original looking and it just wasn’t worth the headaches for me. I hope you get this sorted out.

 

[Curt Chambers]

OK, here we go. With a fresh battery off the trickle charger the battery voltage is 13.3v. I repeated the previous voltage test to get a new baseline. Coil + reads 5v with Ign ON and 8.8v cranking. Something I've noticed about this that I forgot to mention before. With Ign ON, the coil initially shows around 8v, but then immediately begins to drop. Over the next 30 seconds it continues to drop and levels out at around 5v. Maybe that's normal behavior. I don't know.

So then I disconnected the ECU harness from the ECU. Battery voltage is now 12.8v. Coil + voltage is 11.7v with Ign ON and 10v cranking. This was done with the ignition switch, not a remote starter.

I then ran a jumper from the ECU mounting bolt to a known good ground, reconnected the ECU, and repeated the first test. Same results. Coil + reads 5v with Ign ON (after dropping from 8v as mentioned previously) and a steady 8.8v while cranking.

So does this indicate another bad ECU?

 

[RJRENTON]

OK, here we go. With a fresh battery off the trickle charger the battery voltage is 13.3v. I repeated the previous voltage test to get a new baseline. Coil + reads 5v with Ign ON and 8.8v cranking. Something I've noticed about this that I forgot to mention before. With Ign ON, the coil initially shows around 8v, but then immediately begins to drop. Over the next 30 seconds it continues to drop and levels out at around 5v. Maybe that's normal behavior. I don't know.

So then I disconnected the ECU harness from the ECU. Battery voltage is now 12.8v. Coil + voltage is 11.7v with Ign ON and 10v cranking. This was done with the ignition switch, not a remote starter.

I then ran a jumper from the ECU mounting bolt to a known good ground, reconnected the ECU, and repeated the first test. Same results. Coil + reads 5v with Ign ON (after dropping from 8v as mentioned previously) and a steady 8.8v while cranking.

So does this indicate another bad ECU?

Possibly.....but b4 buying another ECM, what ballast resistor are you using? The one that SHOULD be used with the std Mopar ECU, is 0.5 ohms in conjunction with the the std Mopar coil. Perhaps you have answered this b4, i just did not see it. Lower resistance will allow more current flow and possibly damaging the ECM.
#74 suggested an MSD system.....with the Mopar distributor providing the trigger pulse. The MSD is a capacitor discharge system that furnishes approximately 400+ volts to the special coil to produce a very high voltage secondary to the plugs. The origional Mopar electronic ignition system was just to replace the points for almost zero distributor maintenance.
It's possible that the bulkhead connections in the ignition switch circuit path are causing or contributing to the problem and must be painstakingly checked and eliminated.
If you have a FSM for your specific model, it shows the correct distributor orientation and the orientation of the distributor drive gear in relation to the cam gear and the distributor alignment....check an verify.
BOB RENTON

 

[Curt Chambers]

Too late. I already ordered another ECU from Mancini. This time I'm going to check the spark before even trying to start the engine.

I'm pretty sure the distributor is installed correctly. It did run one time pretty good with the current installation, and distributor orientation hasn't been changed.

 

[RJRENTON]

Too late. I already ordered another ECU from Mancini. This time I'm going to check the spark before even trying to start the engine.

I'm pretty sure the distributor is installed correctly. It did run one time pretty good with the current installation, and distributor orientation hasn't been changed.

I understand....just asking the question ..... sometimes in the heat of the battle small things get overlooked.... in the meantime, do you have a way to test the ballast resistor resistance? As I mentioned previously, the origional resistor should measure ~ 0.5 ohms. Please keep us up to speed as to your progress.
BOB RENTON

 

[Bee1971]

Curt

Before installing the ECU , either make sure the key is in the off position and or battery negative terminal disconnected

And


Also , very important, just verify a good ground on the NEW ECU before attempting to start the vehicle or looking for spark

Peace

 

[Bee1971]

I understand....just asking the question ..... sometimes in the heat of the battle small things get overlooked.... in the meantime, do you have a way to test the ballast resistor resistance? As I mentioned previously, the origional resistor should measure ~ 0.5 ohms. Please keep us up to speed as to your progress.
BOB RENTON

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