74' Plymouth Duster cranks but won't start.
 

This car is a 74' Plymouth Duster, with an automatic transmission, and a 318 V8 engine.
Problem is as mentioned in the title: The engine turns over, but does not run.
It kicks like it's going to start every so often, but never actually runs.
There is also an intermittent backfire through the intake manifold. This results in fuel occasionally spurting out the top of the carb.

We believe there is spark, because we're getting light from the in-line tester (verified current).
We've done a compression test, and it passed.
We've checked the timing with a light - it is correct according to the manual.
Fuel is getting to the carb - checked by undoing the line to the carb.

We've tried a number of different things to encourage it to start, particularly Starter Fluid in the carb - this was interesting because the engine did not seem to respond at all to the additional fluid.

So, a few questions:
Does this car have a harmonic dampener, and would it be possible for the elastomer to have failed, thus resulting in the timing being in fact incorrectly set?
Could a bad coil ballast also result in these symptoms?
I have also read about the fuel float in the carb getting stuck, and causing spurting fuel - should I personally disassemble the carb and check?

Additional background:
The car was taken down because of a vacuum leak - both at the brake booster, and a bad OSAC diaphragm.
The carb was rebuilt recently as well with all gaskets replaced - perhaps incorrectly?

Anyway, from there, the car has refused to start but it cranks well.
I'd appreciate any help y'all might have about this conundrum.

Not sure if that car has that ballast and other thing "can't remember the name," it connects to, but that was my problem. My buddy changed them out and it fired right up. But, like I said, I'm not real familiar with that setup at all.

Welcome.

Use a voltage meter and check from ground to coil positive with key in run and then while starter cranking. Let's eliminate one thing at a time before guessing. Light at your tester does not conclude proper ignition voltage.

Sound like a timing chain went. Check cap and rotor too.

Hey everyone, thank you for the replies and insights.
I will test the electrical system properly later this week if possible, and update with the results when I do.

sounds like timing is out 180 degrees

Check the timing marks and see where the rotor is pointing. I'm with moparted sound like the timing chain may have jumped, It is a nylon toothed coated steel gear on the cam. Use a breaker bar and rotate the motor backwards until you see the rotor move then turn it forward (clockwise) and see how far it turns before the rotor moves

Hey guys I'm having a similar problem with a 318. Cranks well, tested both ballast resistor and ignition module both ok but no spark at plugs. checked coil voltage, just over 9 volts on ignition but only 3 on cranking. coil checks out ok as far as coil resistance. It has an electronic distributor(no points just a rotor)not sure of the type Any help is appreciated

9 and 3 is too low, the voltage drop is normal and due to large draw by starter motor that is why when starting ballast resistor is bypassed.

Not knowing what car I would still check connections at firewall bulkhead connector, there is likely a bad connection creating resistance and an unwanted voltage drop from ignition key switch.

I would suggest you start a new thread to get more responses and not get lost in this thread.