Just got my first slant six

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Next problem...

Now it started having a rough idle once warmed up. The alternator and ignition module are about a year old. The carb was rebuilt last year. The plugs are only a few weeks old. I thought the plug wires might be bad and I knew the battery was weak.

Today I replaced the battery, ballast resister, coil, cap, rotor, and plug wires. It started right up and purred for about five minutes the stuttered a bit and died. It starts every time but dies if I don’t keep the RPMs up.

Removed air cleaner and no change even though the filter could use a change. The choke was wide open, not closed.

What are the possible causes of the rough idle and stalling? Air/fuel mixture, timing?
 
Very good on the oil pressure!

Possible causes on the idle problems:
- A vacuum leak, leaning out the mixture; the choke enrichment when cold cold be covering that condition. Start by checking vacuum hoses for cracks or falling off, etc.
- The choke not coming off when the engine warms up and making the mixture overly rich. If overly rich, the plugs will have excess black carbon deposits on them. But it sounds like you eliminated that as an issue.
- Wrong ballast. Too much resistance will kill off a lot of the spark energy as the ballast warms and its resistance goes up. But that usually occurs within 1 minute. Just to be sure, what brand and PN of ballast did you get?
- Other voltage drops to the ignition system.
- Lesser probability IMO: Partial fuel pump failure or fuel filter being blocked.

Do you have a voltmeter? If not, it will be useful to get one for working on this vintage of car. You can check the charging system and battery health and voltage to portions of the ignition system, spark wire resistances, ballast resistance, wiring integrity, etc.
 
Thank you. I’ll check for vacuum leaks and maybe swap out the resistor for the old one just to troubleshoot it. The one installed was a BWD RUE1, which looked the same externally as the old weathered one I removed. I do have a volt meter.
 
Bob Wilkie said:
I just picked up a 73 Dart Swinger with a slant six. I noticed the garage floor where it had been parked was black under the tailpipe. I jump started it and drove it home over an hour and it ran fine and didn’t smoke. The oil light flickered at stops and sometimes stayed on. The engine and compartment are covered in what looks like a few years worth of oil. I checked the oil pressure with a mechanical gauge and it idled around 5psi. I checked compression in the cylinders and they were 70, 80, 75, 75, 75, 80. It has electronic ignition. The plugs were all gapped around .040. They were covered in light brown deposits and one of the insulators around the electrode was gone. I’m hoping to flip the car but it could be a keeper too. I have to replace the engine mounts and tranny mount.

My mechanical skills are low but I’ve been learning a lot from you guys and my friend who is a mechanic. With that info, what are your thoughts for the least intrusive and most economical steps to take next?
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The fact that your compression is fading evenly might be that you have a worn out timing chain. Possibly , in my case that was the issue. The chain was stretched out badly
 
Bob Wilkie said:
The one installed was a BWD RUE1, which looked the same externally as the old weathered one I removed.
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OK I don't have actual measurements on that one but it crosses over to the right application. So it probably is OK. One half should be around 4-5 ohms and the other < 1 ohm. I find plenty of cases where the parts guys at the counter sell folks just any old ballast so I tend to ask. But at this point, I'd put this down on the bottom of your list of things to think about.
 
nm9stheham said:
OK I don't have actual measurements on that one but it crosses over to the right application. So it probably is OK. One half should be around 4-5 ohms and the other < 1 ohm. I find plenty of cases where the parts guys at the counter sell folks just any old ballast so I tend to ask. But at this point, I'd put this down on the bottom of your list of things to think about.
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I had that ballast issue had the wrong ohms man it drove me nuts until I found out it was a five dollar part
 
Yes, the Mopar system ballast resistance value is pretty much the lowest around. Putting in an incorrect higher resistance ballast can really cut back the spark energy.
 
get a vacuum gauge on that and just watch it. Also , after it dies, pull the carb bowl and see what comes out. (does it have a float level port?) a new fuel filter is cheap. You could even run a IV source of gas (gravity feed) and see if it idles past the 5 minute mark. Inverted 1 liter with a 5/16 hose out the bottom and a vent hole hanging from the hood latch...and a fire extinguisher. An uber cheap setup and "keep it Mopar" would be to add a Mopar ECU to the POINTS set up, thats right, tickle it with points!
points.gif
 
Not to beat this to death, but with that 2 part ballast resistor, you have to make sure that the correct halves are connected to the coil and the module. The low resistance half feeds the coil + terminal.
 
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