Died and will not start

[brotow]

My 1970 Challenger with I believe 1971 rallye gauges dash has been running fine, but lately engine had trouble with higher rpms. Now it wouldn't restart after getting gas, It will start and run until I release the key from the start position to the run position and dies.  I replaced the ignition switch, didn't solve the problem. I remember before replacing the ignition switch the coil showed low voltage to it.  I'm running a stock electronic distributor. Does 1971 dash have a seat belt interlock system? I'm at a loss, any suggestions?

[dodgedream]

Sounds like your ballast resistor has given up.fast fix and I would recommend carrying a spare as they are known to fail

[JayBee]

I second the vote for ballast resistor.

[brotow]

Switched out the ballast with a new one, (resistance measured the same). Bought a new ignition control box, no change (MOPAR HR7500 Electronic Ignition Module).  https://www.ebay.com/itm/324317385004   

['Cuda Hunter]

seatbelt interlock system started in 74. 

[jimynick]

I'm not a big electronics guy, but I seem to remember that the coil is supplied a full 12 volts in start position and that it then goes down to about 8 volts if I remember. I'd be looking at a schematic to determine the colour of the run wire- for some reason I want to say it's brown- and check for connectivity at the firewall bulkhead connector- a notorious source of wiring failures and problems. Just my 

[brotow]

Yep. that would be my next step.

[brotow]

My thanks to  jimynick.  Loose? connection in the bulk head connector. never found the reason, it's up and running' moving the wire around did not make it stall out.

[jimynick]

Good to hear you got it! 

[70chall440]

Check the steering column connector as well, I had a very similar issue. I realize you got it sorted out but check the connector just be sure.