Greetings! Long-time lurker, recent poster. I am having issues with my '73 Valiant and would like some help in getting her back up and running.

I'll try to offer as much info as I can.

Iit was upgraded to a Super Six about 10 years ago. The starter turns normally, it just won't "catch" and fire up. I am getting gas through the carb (Carter BBD). The carb was bought from Napa about a decade ago and it's given me good service. The ignition system is the good ol' Chrysler Electronic Ignition setup.

When it does start (which is rare), it runs without ANY stumbling, hesitation, sputtering, etc. It purrs right along. It just doesn't want to start when the engine is hot OR cold. I think the timing was advanced 4-5 degrees (I didn't write it down when I last checked it, and that was about 2 months ago).

I have done the fuel line mod as outlined by Dan Stern, and I did replace the cap/rotor and spark plugs, using the part numbers he posted here (thank you, sir!) That was all done around 1-2 years ago, and the car hasn't had many miles put on it during that time - maybe 1500. I did not (yet) get the Magnecor plug wires. I did try replacing the needle/seat and adjust the carb float. That didn't help.

For the heck of it, I did try a spare ballast resistor and an extra aftermarket (4-pin) ECU to no avail....I had them lying around and thought I'd see what that'd do, but zilch. I have no idea how old the ignition coil is. I know it's not the original one.

I was thinking about doing the HEI ignition upgrade and the electric choke I've read about here on this site.

Any suggestions would be greatly appreciated! I'd like to get my baby back on the road.

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1973 Plymouth Valiant

First place I would check is your coil. Coils can sometimes work intermittently when failing depending on ambient temperature.


Label and disconnect the small wires attached to - & + on top of coil, and gently pull center high voltage wire going to distributor.


Test resistance as shown [url=http://www.international-auto.com/fiat-lancia-electrical-system/how-to-test-an-ignition-coil.cfm]here[/url] using DC volt Ohm scale on multimeter.


When ballast resistor fails, engine will start & run while ignition key is in start position, and once key is released to run, the engine stops running. This happens with Chrysler cars because there are two ignition circuits; one that bypasses ballast during starter engagement providing 12 v to coil, and second circuit that takes over once engine catches and key is in “runâ€￾ or rather “onâ€￾ that run circuit sends current through ballast reducing it to around 6 volts preventing damage to coil.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Don't guess at where the problem might be. Back up a step and do some easy diagnosis. The next time the engine cranks without firing, remove the air cleaner lid and spray a 2-second shot of carburetor cleaner into the carb throat. Crank the engine again. If you get any audible indication that the engine's firing (starter seems to speed up, maybe a sputter from the engine), that tells you the problem is insufficient fuel. If no such indication within a few of seconds of cranking, then hold the accelerator to the floorboard while you continue cranking for another five seconds or so. If you get any indication (starter speeds up/sputter) that tells you the problem is excessive fuel. If no indication, then pull the coil wire out of the central distributor cap terminal and have a helper crank the engine while you hold the coil wire so its distributor-end terminal is about 1/4" away from a convenient chunk of metal (engine block or cylinder head). You should see a consistent blue spark, one for every "chug" of the starter. If you do not, then start suspecting ignition components like the coil. But if you do, then put the coil wire back in the distributor cap and remove one spark plug wire, pull back its boot and repeat the spark test -- this time you're looking for a blue spark once every six starter "chugs". If yes, then you can repeat the test with other spark plug wires if you like, but the problem's probably not lack of spark to the spark plugs, but the plugs themselves would still warrant inspection. If no, then you need to suspect the distributor cap, rotor, and plug wires.

Me, I'd be suspicious of that carb which may or may not be giving you good service right now. "Remanufactured" carburetors from parts stores have a rotten reputation, and mostly deserve it.

Another thing to keep in mind: there was a technical service bulletin for replacement of all '73 and early '74 electronic ignition control modules because the originals had problems that made for hard starting. Don't know how many or few miles you have on your car, or whether it has the original ignition box, but if it does, that would be on the short list of suspects. But you've already tried swapping the ECU, so that's probably not what's causing your problem.

HEI is a good upgrade, but do the diagnostics first so you're not chasing your tail.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan along this same route can you pull a plug and check for spark the same way?

Sorry I did not reply back right away, folks - I was on a trip out of town. I will look at what you have all suggested and get back to you with what I find ASAP. Thank you all!

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1973 Plymouth Valiant

Ok, I got some spare time and went to checking things. I am not getting ANY spark from the coil-to-distributor wire. Since as I indicated in my earlier post that I have tried a spare ECU and a spare ballast resistor to no avail, should I suspect the coil? I do not have an ohmmeter to test the coil itself.

If you folks do recommend replacing the coil, what would be a good one/brand to get?

Thanks in advance to all!

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1973 Plymouth Valiant

Don't guess. Diagnose! Lack of spark at the coil could be a faulty coil, or a faulty distributor pickup, or faulty wiring. What tools do you have? Have you got a test light, a multimeter, anything like that?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks, Dan. I didn't stop to think about that. Unfortunately, I do not have those tools Looks like I may be headed to the store to get one. While I have plenty of other tools, diagnostics equipment like those, I do not have in my toolbox....I must remedy that situation!

If it helps (may be redundant), I did follow your steps on the carb as you posted earlier in this thread and that didn't seem to indicate anything wrong with it (I am aware of the issues with "reman" carbs these days)

Feel free to chime in with anything else you can offer. Be direct!

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1973 Plymouth Valiant

Remove the primary (small) wires from the threaded stud-and-nut connections on the coil. Run a test wire from battery positive to the coil's (+) primary terminal. Connect one end of another test wire to a good ground such as battery negative or alternator housing. Hold the distributor cap end of the coil-to-distributor-cap wire near the engine block, and alternately touch the second test wire to the coil (-) primary terminal and remove it. Each time you remove it, there should be a spark jumping from the coil wire to the engine block. If so, the coil's good (or at least good enough).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks, Dan - I tried your latest tip. I still am not getting any spark using the test wires.

I appreciate you taking the time to answer my (noob) questions

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1973 Plymouth Valiant

Okeh, now it's time to suspect the coil is dead. What kind to get depends on what kind of ignition system you're running. If it's a stock Mopar setup, then a good stock replacement coil such as Standard Ignition #UC-12X ($17.40 at RockAuto!).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yep, stock Mopar electronic ignition. Thanks for all the pointers and assistance, Dan! I'll let you know how it goes with a new coil.

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1973 Plymouth Valiant

Well, Dan, got the new coil from Rock Auto in. Took a few turns of the key, but she fired on the 5th try. Considering the car sat for about 2 months (weather, life getting in the way, etc). Drove the car around for an hour. Tweaked the timing a bit, and she ran without any stumbling, hesitation, etc. the entire time.

Drove home, washed the car and......she didn't start again. So I waxed and vacuumed the car out - figured it's be a good stress relief t stay busy and accomplish something today - and retried the remote starter switch to check for spark at the coil-to-cap wire - annnnnd no spark ( :shrug:

So I tried the test wire thing you mentioned and I was getting a spark when connecting the positive battery to the positive coil terminal (I could even hear the clicking/popping). I was not hearing/seeing that with the old coil. So I removed the test wires and reconnected the coil-to-cap wire - and she fired on the second try.

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1973 Plymouth Valiant