I could use some suggestions on another mystery engine problem. Yesterday, I went out in the garage and started my 340 Dart. I hadn't started it in 3 or 4 months but it started up rather quickly. I ran it for about 5 minutes, shut it off and went in the house for the night. Today, I went to start it again to move it to my other garage and it won't start at all. All it does is crank over and over as though it's not getting any spark. I didn't do or change anything to the car from when I shut it off yesterday to trying to start it today. So, I tried changing the coil but that wasn't it. I also swapped out both the ecu and ballast resistor, again no change. Suggestions on what else to look at are appreciated.

Fuel making it to the carburetor?

How much gas does it have in it, and is the gauge accurate? I've had vehicles that would be out of fuel even though the gauge still shows around 1/8 of a tank.

Yes, there is fuel in the tank, probably 5 or 6 gallons. I don't know why the fuel would have made it to the carb yesterday and not today unless the fuel pump crapped out overnight but I did try squirting some gas in the carb. after it failed to start the first time I cranked it. It didn't change anything.

Have you pulled a spark plug and cranked the engine over to verify if there is electricity at the plug?

Not yet.

Did it get cold there last night? Maybe you need to pump it a time or two.

No, it wasn't unusually cold and I did pump it.

Try holding the pedal to the floor, maybe flooded.
If that don’t work spray a little staring fluid in carb.
If it starts, or wants to start it’s not spark its fuel.
If it don’t start with starting fluid or try to start it’s got no spark

Check the basics first, fuel, air and spark
Let us know what you find, I'm thinking overnight corrosion in the ignition circuit

Might sound odd. . . but check for vacuum leak. I battled getting my 71 challenger started and running right for quite some time, plugs, coil, wires, ignition box etc. . . only to find I had a pretty bad vacuum leak. That $5.00 fix sealed the deal.

put a plug in end of plug wire, put key on, use a screwdriver to jump starter relay and see if plug is sparking. If not take off distributor cap and see if rotor turns when cranking. If rotor is turning, either your distributor went bad, being you changed the other parts, or you have a wiring problem- lost power to ecu or coil

also check for power in the ignition 1&2 circuits, so you are powering the run circuit when cranking, and the coil is getting power in the start circuit.

what kind of timing chain u have on it? If its plastic it could have broke a few teeth off & the chain jumped. Easy enuff to do a chain stretch test to eliminate that problem. Dave ss/ea #1355

I had an old steel timing chain set jump timing when that motor (1959 Dodge D600 motor) backfired when starting it when it was below freezing in the Mojave high Desert during one cold winter

I can't say for sure as I haven't had the cover off the motor since I bought the car. I have an envelope of receipts that came with the car. I'll have to look through them and see if I can find anything on the chain.

I forgot to mention in my first post that I had put a different carb on the motor prior to when all this started. The carb that was on it previously (when it ran good) I put on my other car. The carb I have on it now is a Holley Street Avenger 870 that I bought used a few years back that I was told had only been run a short time while on an engine dyno before it was replaced with a larger carb. It does look like new. I hadn't used it since I bought so this was the first time. I tried starting the car again today and it actually did fire when I sprayed starting fluid in the carb. but it wouldn't stay running, only till the starting fluid was used up and then it would crap out. But, for the few seconds it was running it was blowing a lot of smoke. I checked the mixture screws and they were about 1 1/4 turns out. I reset them to 1 1/2 turns but nothing changed. I'm wondering if the floats might be sticking from the carbs sitting unused for so long. Could stuck floats cause this type of problem? I am going to swap the old car back on it tomorrow and see what happens.

If it starts & runs fine with the old carb, there ya go.

I would certainly disassemble & check over the used carb, and clean & adjust everything.