Runs, drives, dies

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73plumkrazy

73plumkrazy

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Hey y'all, got to pick your brain. I've got a 73 dodge dart sport 340, had it for a couple months now. I had a few electrical issues and finally rewired the whole car. Somewhere in the mix, ignition coil got fried. Replaced the coil, the ignition control unit, and the ballast resistor. The car Started and ran no problem, until it died while I was driving. Wasn't getting a spark. So went through my typical checklist, everything checked out but still nothing. After awhile, went to start it, started like there was never an issue. This happened a few times. The pattern seems to be after it had cooled off a bit, it would start and run. My initial thought was the coil was overheating and it was protecting itself. So I replaced the wires and spark plugs, they probably needed to be addressed anyway considering the wires were 7mm and I replaced them with 8.5mm. Anyway, it's still doing the same thing, seems fine until it's hot, then the car dies with no spark until it cools off. The only thing that hasn't been given any attention is the distributor. Any ideas?
 
Distributor, electronic I assume (no points). If so, it could be the pickup coil in the distributor. When replacing, you will need a brass (non magnetic) feeler gauge to set the air gap.

Welcome to the site.
 
Be sure the Ignition Module case is grounded really well. I run a dedicated ground wire to the case. Remove any paint on the case where the screw goes.
 
Bad Sport said:
Distributor, electronic I assume (no points). If so, it could be the pickup coil in the distributor. When replacing, you will need a brass (non metallic) feeler gauge to set the air gap.

Welcome to the site.
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Thanks! Ok I agree with you. What are you recommending for gap on this?
 
dano said:
Be sure the Ignition Module case is grounded really well. I run a dedicated ground wire to the case. Remove any paint on the case where the screw goes.
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Thanks Dano! Yes I was very diligent about a clean, good ground and I also ran a ground wire.
 
73plumkrazy said:
Thanks! Ok I agree with you. What are you recommending for gap on this?
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I have had the same problem as you are describing on 2 different vehicles. Mine was sporadic, in that I might drive 5 miles and it would quit, let it sit for a bit and it would fire right back up and it may run 20 miles before doing it again.

.008 on the air gap with a NON MAGNETIC feeler gauge lest you damage the pickup.

From the FSM.

20211025_110517.jpg
 
Bad Sport said:
I have had the same problem as you are describing on 2 different vehicles. Mine was sporadic, in that I might drive 5 miles and it would quit, let it sit for a bit and it would fire right back up and it may run 20 miles before doing it again.

.008 on the air gap with a NON MAGNETIC feeler gauge lest you damage the pickup.

View attachment 1715810399
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This is BEAUTIFUL! Thank you!
 
Bad Sport said:
Can't say for sure that's it, but the symptoms align, lol.
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Hey man, it's a step in the right direction. And I've looked under the cap. Whether or not that's it, there's somethings there that need to be addressed lol
 
I have had ECU's (Orange box comes to mind) that when they heat up the circuit board separates and breaks connection. Let it cool for a few minuets and the engine would fire and the car would drive until it happened again.
 
You might want to get another ECM, and swap it in when it is misbehaving. I had a pinto that would do the same thing. Ford had a bunch of heat related ECU issues.

For ground while testing, an 18 guage jumper wire to batt negitave will work.
 
dano said:
I have had ECU's (Orange box comes to mind) that when they heat up the circuit board separates and breaks connection. Let it cool for a few minuets and the engine would fire and the car would drive until it happened again.
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I replaced the ECU when I did the coil because I thought the same thing. You still think it's faulty?
 
73plumkrazy said:
I replaced the ECU when I did the coil because I thought the same thing. You still think it's faulty?
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If so maybe not. What brand did you replace it with?

Have you looked at the ignition switch? They can cause you issues as well.
 
Dana67Dart said:
You might want to get another ECM, and swap it in when it is misbehaving. I had a pinto that would do the same thing. Ford had a bunch of heat related ECU issues.

For ground while testing, an 18 guage jumper wire to batt negitave will work.
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TFI modules for Ford do the exact same thing. But yeah OP, throw anothe rmodule on and see if it does it if it still does rule out he module. Quicker than playing around with pickup gap under distributor cap, although that should be set correctly.
 
Here is an older thread with some good testing steps. Read this thread, mostly the post #4 by @67Dart273 and get familiar with the tests you should perform, then get it acting up again and unplug the distributor connector and try the tests. If it still does not spark you can rule out a distributor issue, if the test is performed correctly. To verify the test, reconnect distributor and make sure it still won't spark while cranking, and then unplug the distributor again and repeat the test.

Diagnosing Distributor - No Spark Chase
 
I had a similar problem after rewiring my Duster. Found one of the firewall block connectors was not making good contact. Removed it, then pushed it back in and used a flat blade screwdriver to ensure it was fully seated. No more issues.
 
Do you have the factory wiring to and from the ballast resister?

Any chance the coil draws too much current for the ECU? might try a stock coil?
 
My first thought is why are you running a large coil with a ballast resistor?
 
If the dist has mileage on it AND the vac adv is connected, the constant flexing of the p/up wires can cause them to break. Seems odd though that this normally random occurrence only occurs hot & not at other times. To check, disconnect dist plug & connect an ohm meter to the p/up. Wiggle the wires. Resistance should be 150-400 ohms & not change. If it goes open cct, bad p/up. Pretty rare, have never seen it personally, but p/up may be grounding internally when it gets hot.
You need to find out what value [ ohms ] the ballast res needs to be for THAT coil. The Chrys bal res is 0.5 ohm. If that coil requires, say, 1 ohm, then the coil will be getting excessive current & will run hot. Coil could have an internal o'heat protection device that is tripping.
Also check that you are getting 12+ v to the ballast res & ECU with the engine running.
 
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