74 duster ,dies while driving

Hey guys,I own a 74 duster 318 that started to stall within the min. or two of driving no matter the eng. temp.Choke opening ok.I will usually get just a couple blocks then its like you turn off the key.When it stalls I still have my 8 volts at coil positive,not ign.switch.I replaced the distributor due to worn shaft,same problem.Replaced dist.twice w/reman.Dist. ground good,even added a jumper to ground,same.Installed 3 new caps and rotors,same.Bought a new pickup coil,same.When it stalls I have coil spark but no spark to plugs.I installed new cap with brass inserts,now it no longer stalls in neighborhood but within a mile or 2 of driving,never stalls at stop at idle,always at cruise.After it sits a couple minutes,it starts up.  

Your symptoms sound familiar.

Try a different spark box...especially if you presently run the orange box. They will fail under load or at rpm's higher than idle.

The chrome box is better.  

thanks for the reply,if the box failed I would have a no spark cond,however i have spark out of coil but not out of cap to plug,although I did repl. module.I do appreciate the reply very much.Thanks,Paul  

Hey Paul, have you tried new  spark plug wires? Sounds to me like you may have a bad plug wire between the coil and the cap. If you have spark at the coil, it should be getting to the plugs if your timing is right, rotor lines up...etc. Do you have full voltage at the ignition module when it quits? Is the voltage right at the resistor, ignition and coil? I know it has to be close for the system to work right. I hate to keep throwing money at parts so I would check that voltage idea first. But if you have a different coil wire, maybe try that too.  

Sounds to me like a fuel problem. i had a car do this once, and had to pull the fuel tank to get the junk out of it.  
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Sometimes you just gotta say...

With a brass feller gauge re gap the magnetic pickup, if you don't have a brass feeler gauge then just eye ball it setting it to where there is just a hair gap between them.

After that buy a new coil.  
age is no lock on brillance

It does sound like a fuel problem,flush out the fuel line with compressed air,from carb back to tank.change fuel filter,possibly fuel line.remove tank  clean out and apply motorcycle tank sealer that can be purchased from motorcycle shop(follow the directions) it ussually takes two sealer kits to coat a cars fuel tank.make sure there is no vapor lock also.a fuel line too close to exhaust manifold or pipes would cause vapor lock.make sure that the carbs float in the resevoir is not sticking as well.check fuel pump pressure,might be time for a new fuel pump.if that doesnt cure it try a new ballast resistor that bolts on the firewall.(its the ceramic white looking strip on the firewall with two wires that connect to it)Hope this helps.Good luck Paul  

the cheapest fix to try may very well be the ballast resistor.probably less than 5 bucks.good luck  

Let us know what the problem finally was paul.thanks  

Hey paul, after it dies and refires, how long does it go before it dies again?  

Hi,thanks for the reply.When it dies ,I wait for approx 2 mins,then it will start like nothing ever happened.Then after a min. or so of driving  it will die again.Before I put the #3 cap and rotor,and good quality too it would after a couple of blocks in the neighborhood.The newest cap and rotor has brass inserts.This made a difference.Now instead of dying every couple blocks,I might go a mile or so,its always at highway speed.At the time of failure ,leaving ign. in on position I had 8 volts to coil positivv and to ign. module,also checked the body grd. and ign. grds,all under 20 millivolts.I just got my accel wires which are only 500 ohms per foot,although I have replaced wires with thousands of ohms per foot and only misfired.The spark is getting lost in the cap for some reason.I have been an auto tech for 32 yrs. and have never seen anything quite like this.I installed plug wires 6 mos. ago.Coil and ballast resistor new twice,even ran external ground wires to see if any change,none.If the wires correct it still wont add up with coil capable of putting out 40,000 volts with current plug wires that arent misfiring.Thanks for your help,I will keep you posted.Paul  

Thanks for reply.Coil is new,pickup coil air gap set at spec. .008 in. with brass feeler blade.I have spark out of coil,not out of cap.Thanks,Paul  

Thanks for reply.It has fuel in carb when it dies.Has spark out of coil ,not out of dist. cap.Problem on ignition side with spark distribution to plugs.Thanks for input.  

If it was fuel the problem would show itself during hard acceleration and at freeway speeds.imo

You say you have spark at the coil but not at the cap so either weak coil and the wire is eating it up or crap plug wire.

but hey, who knows.
let us know what you find.  
age is no lock on brillance

Paul, do you only have 8 volts to the ignition module? Did I read that right? If so,thats too low, you need full voltage to the module, 12.5 or higher. I'm also not sure what the voltage at the coil should be, my car is in storage so I cant check it...... Mopar Performance has a good page on this subject, its the instructions for converting points to ecu systems. Its worth reading to learn more about the system.