I got ready to go to a car show this afternoon.Went to fire up my 73 Duster 340 and it won't fire. Haven't had it out in about 2 weeks. My brother in law and I did some checks I have fuel, starter turns over but won't fire. We changed coils and ceramic box on fire wall, still nothing. What we did find was there is no spark from the coil wire to the distributor until the ignition key is just about to the off position, then there is a quick spark for a spit second.We are thinking that my iginition switch is bad since it is the original one.
Any thoughts or suggestions?
thanks,
old 340dog

Bad ignition module or try moving the bulkhead connector wiring.

ECU or ballast (4 terminal "dual" ballast I'm assuming). Was this (ballast) the white ceramic piece you changed? If so then I'd say ECU or as Stump said clean that male/female brass connection in the bulkhead. EDIT If you have a VOM, in ign2 (crank) 2 terminals on the ECU (blu/yellow and red/green) need fire if it's a 4 terminal "dual" ballast with a 5 pin ECU with a functioning 5th pin (OE ECU) and the coil positive primary terminal nees fire also. In ign1 "run" the coil positive primary need fire to/thru the ballast either thru a 2 terminal "single" ballast or thru the coil half of a 4 terminal "dual" ballast and the ECU needs fire at the blue/yellow wire terminal. Ohm the dist pickup & check the gap. MORE EDIT Pull the yellow wire off of the starter relay when using the meter in the 2 key positions. You know the starter works & no need to run the batt down or listen to the noise distraction while you are diagnosing

I would bet on the ignition switch. I had a 62 power wagon that had a bad switch and you would crank it get it spinning then let the switch go back to run before it would fire!

my 73 340 Duster had a problem with the power wire for the ignition at the bulkhead...

Thanks for the information and suggestions guys. I did switvch out the ceramic ballist last night when I first noticed the problem. However it was a used one I had. I'm going to pickup a new one. going to check some connections and distributor as weel. Before I get involved in a ignition switch change. It is weird that the car have been running great and have had no problem. This was the first time out with it in about 2-3 weeks, so it even made it more strange. Something else I did remember later last night was that from time to time when the car was running just still at idle etc. It would stop running,but would restart as soon as I turn the key.
Thanks again, I keep everyone posted., hopefully it's a easy fix.
old340dog

I don't know why everyone jumps on the ballast resistor it's bypassed in start.

check the air gap on the pickup coil inside the distributor...

need brass feeler gauge .008

Had a problem starting my van when I first got it, If it ever started, it would run good until shut off. Did the usual checks, but then found that the pivot pin on the breaker plate (electronic ignition) had broken. This caused the plate to be cocked off to the side, and every once in a while, it would fire. That was a new one on me.

Thought I would give everyone a update. Stoped by NAPA after work today, they had to order a new 4 prong ballist resister. I'll have that tommorrow. But I did get a can of spray electric contact cleaner.
I figured I'd do some simple cleans and checks tonight. Then move to the ballist replacement, if that didn't work.And move on to something else, going by things systematically.
I sprayed and cleaned the electric plugs, contacts points one the ballist, electronic module control box and steering column plug in under the dash.
To my surprise and relief the duster started right up.Seems to run pretty good. I do think I will put the new ballist in when I get it.
Thanks to everyone for their input and suggestions.

A poor connection. Glad ya got it. Sometimes we need things to go our way

Well after several months from my problem with my duster not wanting to start,my old problem is back. It started right up after sitting in garage for about a week. (I haven't had any problems since my last post.) It ran for about 10 minutes while I got my tractor out to mow. When I got ready to put in back in the garage about an hour later it won't start. We got it pushed back into garage. A friend and I did a check while I turned engine over and after letting the motor crank about 10 seconds there was only 3 sparks from the coil wire and they were yellow in color.
I said the heck with it since it was late and put my battery tender on battery since I thought the battery may be weak from cranking it muliple times. Last night I happened to be in garage so I thought I would see if would start. To my surpise it fired right up.
So my question am I dealing with a faulty iginition coil or the orange ECM box on the fender well? Or is it something else.
thanks,
old 340dog

Friend had a cuda in high school ( brand new 71??) with the same problem under warranty.. Turned out to be the electronic box.. Dealer installed a chrome one after the first two orange ones were bad straight off the parts shelf.

I remember this distinctly as the dealer ( car was under warranty) was scrambling to fix this.. Same situation, dealer changed out the ignition switch because we could hold the switch on partway ( to get us home at times).. Problem was intermittent ( like yours)...

New chrome box was the fix..

Check your voltage at the coil. My similar problem turned out to be the coil.

Had a similar problem with my 1974 Duster. Finally traced it to a loose connection where the steering column to the under-dash wiring harness connected. Just about every round connector was worn. I simply soldered on new individual terminals and haven't had a problem since. Been 4 years now with no intermittant start problems.

Mine does this once in every 50 or so starts. I've changed the switch, the ECU and the resistor. Nothing ever seemed to change. I found that when it does it to turn the switch all the way back to accessory a couple times and then try to start it and it hits every time.

I only use Mopar ignition as backup after all the pickups and control box failures I have found that the late 80s factory control boxes work good and don't just fail . My change to Pertronix and never had a issue and or points but I'm old skool You also may want to check the wiring down the steering col for burns or breaks My 73 had burnt / broken wire in main harness also you may want to check the engine ground