Dany's Magnum swap is back!! with Ignition woes now..

-
M

motorpirate

serial mopar owner
Joined
Nov 4, 2007
Messages
720
Reaction score
557
Location
northern KY
Well the track finally opened here and we got a chance to test the new trans/converter.
But with the temp being so high that day, the 45 min trip on the interstate and the long line into the track and thru tech the car got pretty hot, 217 degrees !!
her first launch it started popping out the exhaust at about 3K like the ignition was breaking up.
Reminded me of how my old Shovelheads would do with a bad condenser.
We let it sit for an hour or more and Nick my youngest gave it a try and it did the same thing.

So I took it out on the main road to the track, and it drove completely normal unless you floored it until 3500/4000 RPM and then it began to miss.
Couldn't really hold it like that on a public street as long as on the track but I got the idea.

It sat overnight at the house and on the drive to the shop the next morning I was able to get on it on a straightaway and it pulled fine.
But by the time I reached the interstate the temp was 205 and I hit it pulling on and at the top of 2nd it started to miss a little.
So I'm thinking this is heat related breakdown of something in the ignition system.

It is as follows:
MP electronic conversion "Kit" NOS from the mid '80's.
Japanese orange box, Distributor and wiring harness. Been on the car maybe 3 years, less than 3K miles since it was installed on the original 273.
Original coil from the 273.

Standard Ign wires, unknown age, but OLD!!
The wire looms on the wires I made when I was 12 (I'm 54 now..lol) so we are going to start with wires/cap rotor.

This is a pretty tame combo and we are shifting at 5K RPM so I don't think we need a "Killer" ignition system, but if I'm gonna replace stuff...

So our questions are this, If the problem persists after the wires/cap where would you go next?
Coil?
Orange box?

I am intrigued by the FBO setup and have one of their limiters in the MP dist now.
But at $260 there goes the drag radials again!!
And I'm just not sure the combo needs it.

I can rob a "test" module and coil off the wifes duster as a test but wondered what the next step above what I have now is?

Pertronics Flamethrower coil?
Which one with the orange box?
Can I eliminate the ballast with an aftermarket coil, and will it be any help to do so?

If it ends up being the Orange box, does anyone make a decent replacement in our China incrusted age besides FBO?

Or is a GM HEI module conversion the way to go?

I think I have given myself TOO MANY OPTIONS!!

Here is the setup we copied:360 TrueStreet Magnum Build
 
I can tell you, I've had nothing but bad experiences with the Jap made pick-ups..
A Standard Ignition piece may be the cure. you could call that a $22 experiment, but much cheaper than your grocery list..
 
'63GT said:
I can tell you, I've had nothing but bad experiences with the Jap made pick-ups..
A Standard Ignition piece may be the cure. you could call that a $22 experiment, but much cheaper than your grocery list..
Click to expand...
Interesting. Our family shop (1936-2000) had lots of Mopar factory Electronic cars though it over the years and most of the problem with stock cars was either the module or module ground. I could always swap in the wifes Distributor as a test too I guess.
 
Also, with it idling wiggle the wires going to the ballast. I chased a problem a few years ago where anything over 60mph it would miss. I finally found it by accident when I bumped the wires going to the ballast and it died. The resistor wire in the ballast was broken, but making contact and I guess at speed the underhood wind was moving the wiring enough to make it break contact on and off causing it to miss.

Free to check anyhow.
 
These can be tough to find, simple in the end. Simple as a coil going bad

Go through the ignition "one end to the other"

You said plug wires are old. Start there, you need them anyhow. Check resistance of them with an ohmeter "just to see". ESPECIALLY check the coil wire

Inspect rotor cap condition. Check for moisture, debri, carbon tracking, and check the rotor CAREFULLY and UNDERneath for spark "punch through" to the shaft

Change the coil......This is a shot in the dark, but coils do this, and there is NO WAY to test them other than try another

Check and improve the grounding on your ignition box. Clean/ scrape around the holes front and back, and the holes on the firewall, remount with star lock washers. Pull all connectors, inspect with lamp for corrosion, etc, and push/ pull them all in/ out several times to scrub the terminals.

Then check voltage. with engine off, and key in "run" check ballast resistor voltage each side. "Key" side should be "same as battery." Coil side will be much lower perhaps 6-10V Again, there is no way to check the coil

Suspect your tach if you have one. Disconnect everything from coil NEG except the wire from the box, and see how that runs.

And last, suspect the plugs

NEXT
++++++++++++++++++++++++++++++++++++++++++++++++++++++

A flat cam can cause this along with certain carb / fuel problems.................................
 
If your engine has hydraulic lifters;
and it breaks up at ABOUT the same rpm, unrelated to throttle-opening, then you are likely looking at valvesprings or possibly an ignition coil.
If at exactly the same rpm, then likely the amplifier.

But if she breaks up at various rpms that can be directly aggravated by the throttle opening, that is most likely spark plugs, coil, or fueling. But if at mid rpms, then NOT likely to be ignition related.

So, if you can drive thru the breaking up, by reducing your throttle opening,I'll guess your plugs are cooked. I would install new colder plugs and probably enrich the related fuel-circuit.
But if you cannot drive thru it, and the engine rpm goes flat, then I would check the valve springs, or the mufflers.
But if the rpm does not go flat, forget the valve springs, and check your gas for water.

But if you have solid lifters, check your hot-lash.
That's the best I got.
 
motorpirate said:
Interesting. Our family shop (1936-2000) had lots of Mopar factory Electronic cars though it over the years and most of the problem with stock cars was either the module or module ground. I could always swap in the wifes Distributor as a test too I guess.
Click to expand...

Yes, that's true! in the early days, that was usually the problem. But since a lot of these Ign parts are being Mfg over seas where the QC is abysmal, and they really don't care quite frankly.
There's plenty of time to over-think it and make it more complicated than it needs to be. My 2c
 
I could be way out in left field, or perhaps I missed something when I read the post. It doesn't do it when the motor is cool, but does it when it's over 200* ? You said the next morning it pulled fine until 205* then the miss returned? Are you sure it's not fuel related?
 
318willrun said:
I could be way out in left field, or perhaps I missed something when I read the post. It doesn't do it when the motor is cool, but does it when it's over 200* ? You said the next morning it pulled fine until 205* then the miss returned? Are you sure it's not fuel related?
Click to expand...
That's right, Heat related.you can hear and feel it popping out the exhaust when its missing.
 
Before you go crazy troubleshooting this, try to borrow (or buy, worst thing you have a good spare) a known good ECU. I also ran an external ground wire to one of the bolts on mine. This is an easy cheap thing to try.

Cley
 
89on35s said:
Before you go crazy troubleshooting this, try to borrow (or buy, worst thing you have a good spare) a known good ECU. I also ran an external ground wire to one of the bolts on mine. This is an easy cheap thing to try.

Cley
Click to expand...
Our plan is to replace the wires/cap rotor today as they are 40ish years old.
And then to "borrow" the ign module and coil off Denise's duster one at a time.
I'm trying to use this as a teachable moment about the diagnostic process for Dany and Nick.
And the module has had a ground wire since it was installed 2 or 3 years ago.
I am betting its a module or a coil but like I said, a teachable moment..
 
That's great that you are teaching your kids! Then they don't end up like me trying to figure all this stuff out at 45 years old!

Cley
 
Well nick and I made up a set of wires today and replaced the cap and rotor and got 3 test hits in with it at about 200/205 degrees and it pulled fine!!!
I think we will take Denise's module and coil with us to the track next time just to be sure..
 
motorpirate said:
Well nick and I made up a set of wires today and replaced the cap and rotor and got 3 test hits in with it at about 200/205 degrees and it pulled fine!!!
I think we will take Denise's module and coil with us to the track next time just to be sure..
Click to expand...
Always a nice feeling getting positive results :)
 
You must log in or register to reply here.
-

Back
Top