67 Barracuda Ignition Issue

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DallasMan2000

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67 Barracuda with 1975 360 and electronic ignition.

Just bought this car two weeks ago from this forum and understood when I bought it there was some work to do.

So here is the issue…. When test driving the car it died and would not re-start. We originally thought it was a gas issue. Added gas and cranked for a while and engine would not fire. Suddenly it fired and we were able to get it back to the house. The engine would fire occasionally for short periods of time between then and when I transported it home.

Began troubleshooting in the garage with a test light, volt meter, and spark tester. This car has a 4 pole ballast and I get 12.5 volts at all 4 poles with the car in run position. Both the coil positive and negative get 0.632 volts with the key in run position. Picture of the ballast and a wiring diagram (from this site) are shown below. I unplugged the top plug on the ballast and got 10.5 volts coming to the right side of the plug (brown and blue wire) with the car in start position. Pin 1 in the ECM plug gets 12.5 volts with the car in run position. Positive side of the coil gets no voltage increase with the key in start position. Run a jumper wire from the battery positive directly to the coil positive and the car fired immediately. I have changed the ballast, ECM, and ignition switch with no voltage changes from those described above. There is no continuity between the top right ballast plug (brown and blue wire) and the coil positive.

Any ideas?

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Current will flow both directions through the resistor so finding power on both all the way back to the switch is normal. You have a voltage drop somewhere. Check what is coming in and what is going through and out at the switch.
 
Here are some of my amateur electrician observations:
1. The 12.5 volts at all 4 poles of the ballast seems correct. Guessing the top 2 poles would likely drop due to the ballast once current is applied.
2. Seems like 10.5 volts at the top right ballast pole is low with the key in start position because start position should provide 12.5 volt bypass. I am guessing that 10.5 volts would be enough to start the car though if the 10.5 volts went to the coil positive.
3. Should the top right ballast plug (brown and blue wire) connect directly to the coil positive or does it go through some other plug, harness, or electrical device? The car has a new wiring harness (lots of wrapping) so I cannot follow the wire back from the coil without unwrapping the harness.
4. Seems like the ECM is not a problem because the car starts with power to the coil.
 
Does it die when hot/warm then start again say 5 minutes later? If so bet it is a ECU or pick up coil. Especially if it one of the newer orange ECU's. Have a picture of it from the top?
 
Well it began as a quit when hot thing, but now it just won’t fire without getting power to the coil directly. The photo above was of a replacement box bought at Autozone that is black instead of orange. I did put the orange box back on. Here is what it looks like now. Do you know if the ECU has anything to do with power getting to the coil positive?

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DallasMan2000 said:
Well it began as a quit when hot thing, but now it just won’t fire without getting power to the coil directly. The photo above was of a replacement box bought at Autozone that is black instead of orange. I did put the orange box back on. Here is what it looks like now. Do you know if the ECU has anything to do with power getting to the coil positive?

View attachment 1716141145
Click to expand...

I noticed the ECU sitting on the fender apron. Take it off, scuff the mounting points down to bare metal to ensure a good ground.

Common problem.
 
Thanks for the response Super-Cuda. That was one of the first things I did. Also tested the casing to battery negative with continuity tester to verify it was grounded.
 
I am suspecting that ECU since it is a "fake" not a real transistor. They get hot and fail a few times before they stop completely. Mancini kit? FYI that black box on the firewall is a Mopar voltage regulator. Beware of the parts store ecu's most are china.
 
Same exact issue? It is a overseas one also. Wish you were closer I have testers for that system. Still can be the pick up if so. Dam I am out of the troubleshooting with a meter books, have to get more made up. Makes it super easy to troubleshoot with common tools.
 
DallasMan2000 said:
Here is a picture of the black ECU that I tried from Autozone.

View attachment 1716141185
Click to expand...

I'm following Halifaxshop's lead on this one, having ran into the same problem. Get an original Mopar ECU and ballast resistor. They are still available and reasonably priced.

Any Chinese made stuff is junk. Problems waiting to happen.
 
I have some still if needed. Mostly tested old NORS though. Let me find the ad.
 
Super-Cuda said:
I'm following Halifaxshop's lead on this one, having ran into the same problem. Get an original Mopar ECU and ballast resistor. They are still available and reasonably priced.

Any Chinese made stuff is junk. Problems waiting to happen.
Click to expand...
Sounds like his ballast is fine.
 
DallasMan2000 said:
Here are some of my amateur electrician observations:
1. The 12.5 volts at all 4 poles of the ballast seems correct. Guessing the top 2 poles would likely drop due to the ballast once current is applied.
Click to expand...
No it is not correct, if the system is connected.

DO NOT troubleshoot willy nilly. When you make measurements with connectors separated, you can lead yourself down "the path." Taking a measurement is useless if you don't know what it means.

Start at the coil. Turn key to run, take a voltmeter reading from coil + to ground. That reading SHOULD be somewhere between 6 and maybe 10V. THAT IS BECAUSE the key provides power to one side of the ballast, through the ballast, through the coil, and then the coil NEG is grounded through the box circuitry and the BOX GROUND meaning the BOX CASE. That is your current functional path

THE CURRENT through the coil DROPS the ballast voltage which is why the coil should read BELOW battery. That is "normal."

If that reading is quite high, AKA near battery, it means the box is ungrounded, the box is bad, the box connector is iffy, the coil is bad, or a loose / bad connection in that path.

The box MUST BE GROUNDED. Unbolt, clean, scrape, use star lock washers
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Start/ crank/ ballast bypass function:

When you crank the engine WITH THE KEY (and not jumpering the starter relay) you have an entirely DIFFERENT setup. Now you have the IGN2 circuit from the key in play. This is a separate contact in the ignition switch designed to bypass the ballast for starting, to give a good hot spark. BUT IT IS A TRICK

Clip meter to coil and ground, crank engine WITH KEY, and take reading. Coil + should be at or near "same as battery."

The RUN LINE GOES DEAD during cranking. HOW DOES the box get power for starting? The power from the coil + bypass circuit BACKFEEDS through the resistor and to the box, meaning, yes, you got it, the box sees LOW voltage during start. Don't ask me, I did not design it.

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Separate distributor connector. "Rig" a spark gap at coil tower USING A PIECE OF WIRE, and NOT the coil radio resistive wire. Rig the gap to 3/8 or so, and take the engine bay side of the distributor connector. "Tap" the exposed terminal to ground and each time you do that, should produce one single "snap" hot blue spark
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Pull distributor cap. Examine for carbon tracking junk, water, etc, and examine pickup and rotor for excessive rust, debri, and strike damage. "Feel" for shaft play. Consider checking reluctor to pickup gap

Check distributor pickup for continuity. There is some argument as to acceptable resistance readings. If it is continuous, that is good.

BE VERY SUSPICIOUS of the distributor connector. Examine for corrosion, "work" in/ out several times to scrub the terminals. I sometimes use a .177 caliber brass rifle brush to clean the female terminals.

Attach your voltmeter to the dist. connector on low AC (NOT DC) volts. Crank engine, and dist. pickup should produce about 1V AC

Check the box connector. Examine for corrosion, "work" in/ out several times to scrub connections.
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INTERMITTENTS Maybe I don't have to tell you this, but they are the MOST difficult. I HATE THROWING MONEY at a problem, but intermittents are different. Sometimes you just have to close your eyes and gamble.
 
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Hello 67Dart273. So I took a voltage reading at the coil and got the same as before. 0.682 volts. See pic below.

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I wanted to make sure the meter was reading correctly so I took a reading across battery and got 13.1 volts. See pic below

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Just for grins, I took a reading with the key off from the battery to coil positive and got 2770 Ohms. My meter switches automatically. Don’t know if this means anything.

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Here are the male and female ends of the firewall harness. Anyone see an issue here? Also, anyone know which sockets the “key on” and “key start” come through? I think we are looking for corrosion or something else that would cause a weak connection.

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