we are new to the forum and to mopar. just bought 73 barracuda for a project that has been sitting around 10 years. said it ran when parked but getting no fire from electronic ignition so i replaced it with 1 wire hei. i got hot wire from plug to ecu but when turning over it drops voltage to 7 volts. not enough to start motor but when i run a hot wire from battery it fires right up.(by the way it did that when it had electronic ignition also, just put 12 volts from battery to coil), any thoughts would be appreciated.

 

Your having voltage drop in your wiring harness, likely at the bulkhead (firewall) connections.

Usual running current flows through the ballast resistor to drop voltage and not overheat the coil.

When starting it bypasses the resistor and sends 12V directly to coil because at starting there is a usual voltage drop due to the starter motor opoerating.

 

You have to understand how Mopar ignition switch / starting works.

The ignition switch of course is several switches in one enclosure

1--Ignition run traditionally dark blue, is called "IGN 1" by Ma. It is hot ONLY IN RUN and is NOT HOT in start. This is important, as the bypass circuit must be active

The run circuit comes out the bulkhead, and supplies several circuits, ignition, alternator field, regulator, electric choke if used, and some smog doo dads on some years.

2--Bypass, traditionally brown, is called "IGN2" and goes from the switch, through the bulkhead, to the coil + side of the ballast. THIS MUST BE jumpered to the "run" wire above when bypassing the coil resistor. It is the ONLY circuit which supplies power to ignition during start

As mentioned above, loose connections can drop voltage

Generally, these loose connections follow this path:

From start relay battery stud, fuse link, through the bulkhead, to ammeter, to fuse (some years) to ignition switch connector -- through switch--back out switch connector

So there is SEVERAL places where voltage can drop.

If you don't have one you NEED to get a FACTORY shop manual. There were changes in 72--73--74, etc, so it's important to have the correct manual.

 

was the ballast resistor by passed when you set up the HEI that needs to be done, if not you would get the voltage drop to the coil when running. The HEI needs full power, Also did you change the coil?
Other wise the above mentioned by Coronet and 440 is dead on.

 

I agree.... HEI needs 12 volts all the time.....

I think you can pick up the hot wire you'll need from the CAR SIDE of the ballast with both starting circuits. Just add the extra wire to you HEI and you'll be good to go.

 

thanks guys you gave me lots of things to check and i understand the wiring method a little better. i agree i need a good shop manuel so where can i find one. your help is much appreciated.

 

http://www.autobooksbishko.com/Items...nual/3122.html

 

Welcome to the forum..... Be sure to check out the Mopar of the Month contest... I learned something from your question and the answers from our great members!!!

 

Welcome!