72 dart - 1bll Holley 1920

So I replaced points with Pertronix ignition kit and flamethrower coil, rebuilt the carb, did the fuel line mod, adjusted valves....

I saw a great improvement after completing them. Night and day. . .

Then, same tank of gas, it started to run sluggish at a stop. Give it a little gas and all good. Within a couple days it started dying, but would restart. A couple days later It was having a hard time starting and wouldn't run very long before dying. Now it wont start or run. Might start once in a long while, might run sluggish like cold for 10 sec and then die.

Replaced the filter with a plastic see through type and fuel is getting into the carb.

I was thinking I loosened something up in the carburetor when I cleaned it and it slowly worked its way to a complete clog. However, if I spray fuel into the carb it wont start then either.

I can smell fuel so I am pretty sure its not a fuel issue.

I'm thinking timing / spark but why would it have ran for a week, and slowly worked towards not running anymore.

Would a vacuum leak prevent it from running? I took off the air cleaner today and it started a few turns later but died. I'm thinking pure coincidence, but......

I have been doing so much to this mechanically that my head is spinning. I am looking for direction on where to start trouble shooting this spark/air/fuel issue.

My non-comprehensive reply:

Have you tried to diagnose the problem systematically?

That is to say, have you sequentially tested each relevant system to determine where the problem is?

To express this more colloquially: Suck. Bang. Blow.

You need compression, valve timing, spark timing, correctly atomized fuel, and a proper spark.

In general, start with the last thing you f**ked with, in this case your ignition.
Do you have a spark?
Is it a nice fat blue spark? Having a high voltage volt meter is a plus, but, in general, you should have a spark that can jump about half an inch.
Is your ignition timing correct?

You also f**ked with your carburetor.
If the carburetor is completely inoperative, or if you have no fuel supply at all, pouring a bit of fuel down the throat, or spraying some starting fluid in there, should get the engine to at least fire a bit. It sounds like you did this and there was no effect.
Make sure. You need to eliminate things.

You also f**cked with the valves.
Odds are you didn't adjust the valves so wrong that the engine won't run at all, even more so that it worked fine and then stopped.
If you have any doubts, check your compression, to eliminate that.

Next, start swapping parts. I'd start with the electronic doodad, since electronic doodads tend to fail, and often do so slowly or intermittently.
If that doesn't do it, then try the hot rod coil. The guy who sold me my car had just replaced the original coil with a fancy Edelbrock coil.
Guess what? Failed in the first week.
If the package has the word "China" on it, it is suspect.

There ain't much to these engines. If coche no va, it's probably some newfangled part you installed, or you f**ked something up.

Good luck!

– Eric

Thanks for the reply. I am going to start going through the systems but am trying to identify first what would cause the system to slowly stop working the way it did. First it runs rough and a stop, then dies at stop, then starts hard, and now wont start.....

logically I feel like i could have dislodged / lodged something deep in the carb. logically, the more it runs the deeper the block gets and now it doesn't run. However it doesnt fire over with spray in the carb.



The hunt continues.

Electronic failures can definitely behave like this, whether after years of use, or brand-new and bad out of the box.

My money is on this, but, I emphasize, this is not a systematic evaluation, and my crystal ball is at the cleaners, so I am not really speaking on the basis of anything concrete.

If I were going to try swapping any parts, I would start with the ignition, and I would start to test each component at a time when it is not working (not when you first start the car and it runs).

First step is to determine whether you have a good spark, when the engine is not working.

– Eric

Also, you DO have a copy of the Factory Service Manual for your car, RIGHT?

MyMoPar doesn't show one for a '72 Dodge, but it does show one for a '72 Pymouth.

They will describe a reasonable troubleshooting framework.

– Eric

Reinstall stock coil. If that doesn't fix it, reinstall points. Report back.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Yes I have a manual - love it, I have a voltmeter - love hate relationship,

Alright, long story figure out what it was. The fuel system I had pretty surely, eliminated. Because it rarely starts and then emmediately dies, I was pretty sure it wasn’t an air problem.

Checking ignition.

Switched out coils because it’s quick - no change. Checking the wire - no spark in coil wire. checked resistance of ground, ignition volts….

Pulled a plug and no spark….. all wires have solid connection.

Pulled cap and all looks like it did when I installed the pertronix kit.

Pulled out the installation instructions and backtracked the steps.

Long story short my gap was beyond useable. I readjusted the gap and reinstalled.

After overcoming a week of flooding, it started and ran quite well. Even with me jockeying the carb to keep a cold engine running it ran well and didn’t try to die due to air/fuel/timing problems. Turned off, turned on, turned off, turned on……. Hearing it run is so nice.

Thanks for you response MDchanic,

You're welcome.

If I may ask, what was the spark plug gap that didn't work, and what gap did work?

Also, what is the primary resistance of the coil you are using?

Others with Pertronix pickups may want to know later.

– Eric

It wasn't the gap of the plugs. It was the gap of the magnet trigger that replaces the points, in the distributor. It comes with a plastic gauge but when I tightened mine down it wasn't tight enough and allowed the magnetic arm to slowly move. Instead of being within X from the center, it was resting against the outer housing. It is probably why it slowly went out of operation. It slowly slipped out of distance.

I don't remember the voltage. The instructions had a troubleshooting area and as long as I was within the boundaries I moved on.

Now I need to adjust timing which I am cool with.

Ah, a perfect, and fairly Pertronix-specific, explanation for your symptoms.

Glad you got it fixed!
I am curious about the performance of the Pertronix system. I have heard it reviewed very positively in other applications (1950s Mercedes, for instance), but haven't really seen much mention of it in the \6 (maybe I haven't looked).
Most of the ignition upgrades I've seen written up for the \6 have been later Chrysler electronic systems or HEI systems, both of which are good, but both of which are, at base, predicated on the availability of cheap plentiful parts from local junkyards, and it's been my observation that those are growing fewer and farther between, which reduces the practical and financial advantages of those improvements, and makes the $200 Pertronix system look better.

I know that you can't say as much as you might, seeing as how you improved three different things at once (adjusted valves, rebuilt carb., and changed out points system), but I would still be interested in knowing how far out of adjustment your valves were, how leaky and dirty your carb was, how burned and out of adjustment your points were, and exactly what sort of improvement you felt after you made the changes, in order to be able to have some vague subjective sense of the type of improvement you experienced.

Personally, I've had just a bit more roughness in my idle that I can't fully nail down, with what looks like one cylinder just a couple of degrees out of time on both the oscilloscope and the distributor machine, and all the usual measures and adjustments completely fine, so I might consider trying one of these at some point in the future.

Thanks,

– Eric

When I bought my car it had been sitting for about 5 years. I thought I had a good knowledge base for dodges as I have a 73 charger and 73 cuda W/318. I was mistaken. I've had to go further into systems than I have before.

Since purchase:

I couldn't get it over 2K RPM and it wouldn't shift. The linkages and cables were crap. Now 3.5-4k if I smash it and I have kick down. Still not a 1/4 mile car by any means.

I don't think my carb was a big problem in any particular way. Yes my car ran better after rebuild but I've also found my float spring was missing and a few other things were off. Someone did a poor job or tinkered with it. The car ran ok with it before rebuild.

I learned how to adjust the valve lashing from you guys and it was simple. There were a few new springs so there had been some head work in the past. Only a few gaps were out of spec and the rest were fine. I don't think this made a huge difference in efficiency.

The compression is so/so. After 20 cranks it hits great compression but it takes a minute. The plugs had spark but I felt like the /6 should have more power.

The Pertronix point replacement ignition was simple to install (unless your me I guess). And the flame thrower coil was a drop in.

It felt to me like a night and day difference.

The carb still needs adjustment, I need to time it, and there is more tuning I need to do. As I fix one system I am having to go back over other areas and fine tune things to work the way I want them to.

I am still getting horrible MPG 10-12 maybe. Once I get the fuel system and carb, and the ignition system where I am confident, I am going to focus on vacuum and make sure all my lines are new and tight, without problems.

The pertronix ignition was within reason a cheap drop in with positive reviews. I've been happy so far.

Okay. Good information. Thank you.

Obviously, nobody can rationally judge the contributions of each of the defects you've found to your initial poor running, but by your description, it sounds like the Pertronix really helped.

Were you able to take a look at your points, or had you replaced points and condenser previously?

Burned points will definitely cause poor running by increasing resistance to the discharging of the coil's primary winding, and a worn points rubbing block, resulting in a too-close point gap, will reduce your dwell angle, reducing primary winding discharge time, and will also retard timing.
Did you happen to check your dwell and set your timing before you installed to Pertronix, for comparison's sake?

Were the valves you had to adjust too-closed or too-open?
Some folks had felt their \6s ran a bit better with slightly increased valve clearances, though I stick to the specified values myself.

If you haven't really dialed in your ignition timing yet, then that's an important thing to do. Retarded timing will definitely cause poor fuel economy, as well as reduced power and increased engine temperatures.
Aside from that, unless your carb is essentially pouring extra fuel into the cylinders (evident from black plugs or very gassy-smelling exhaust [Note: If you're below about 50 to 55 yers old, you may not have an intuitive sense of what a properly-adjusted non-catalytic-converter car is supposed to smell like] ), you should NOT be getting that kind of mileage, and there's something wrong somewhere.
Don't ignore simple things like brakes dragging.

– Eric

Because of the way I bought the car I decided to just replace the points with new ignition - plug and play parts. Im still going through all the systems. Trying not to touch what’s not broke ….. most are broker . I found an issue with the fuel system today which contributed to my last problem.

A few valves over a few under. I could hear one of the valves and it was the only one really loose. The rest were pretty good.

I’m doing all the work myself so I’m going slow and steady. Learning a lot about the 72 dart as a whole. Cleaning up 52 years of different peoples skill levels has been a challenge.

I’ve got a cheap rpm gauge on order that I am going to instal in the engine compartment to help with both timing and carb adjustment. Vacuum gauge still in box. Working on new vacuum lines to ensure no vacuum leaks but need to find the right ones.

I’m looking forward to the timing adjustment. Once that is done, I feel like the work I’ve already done to the rest of the engine systems to get the car where it is now, should be basic enough to let me set them more permanently.

The upside to the HEI and the downside to the Petronix is the fact that you can walk into any parts store and get a new HEI module. Not knocking the Petronix. Most people say they work great with little problems also. I installed one on our forklift and it works great.

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

So, the points could have been completely shot, or just way out of adjustment, thus accounting for at least part of the improvement you noted.
Or not.

Annnnd... What's up with that?

So, unlikely that played a major role.

But isn't that really just life, pretty much all the time?

Yeah. All of that's gotta be done before you can really say much.

So you haven't actually set the timing yet?
Coming down on a completely different timing setting (probably more advanced, especially if original points rubbing block was worn and timing was very retarded) could explain any "night and day" improvement in running as well.

Thanks for all of the information!

– Eric