72 Cuda Starting Issues

[Dodgem Doug]

I'm lost, frustrated and running out of patience!

I've got a 340 with electronic ignition. Everything is new, Mopar Performance Distributor, 5 Pin ECM, 4 Spade Ballast Resistor, MSD Coil & Wiring Harness and ignition switch.

The car will start when I let off the key ignition not while cranking. I've checked all my wiring connections, checked the resistance on ballast resistor, verified all the wiring on the ECM to make sure there's no shorts in the new wiring harness and have even put a new ECM on and the only thing I've found during my checks is the distributor pick up is a tad low on resistance. Should be I believe 350-500 ohms and mine is 260 ohms. Will this cause the car from starting. Any suggestions or tech help is greatly appreciated!!! 

[RSI700VIPER]

Not completely certain but I believe the MSD coil requires 12 volts to run properly.  You will need to bypass the ballast resister on the firewall. 

[RSI700VIPER]

FYI - When cranking, the starting circuit bypasses the ballast resister delivering 12 volts to the coil.  When you release the key, the power to the coil gets diverted through the ballast resister and steps the voltage down to 7 volts to prevent overheating the stock coil. 

[Dodgem Doug]

I had a new stock coil on before I put the MSD on it. I thought maybe it was the coil but it didn't make any difference with the starting problem.

[Burdar]

The brown wire that comes out of the ignition switch is what powers the coil during "start".(and bypasses the ballast)  Once the engine starts and you let off the key, power transfers to the blue "run" wire.  That comes out of the ignition switch as well.  Since the car doesn't start while cranking, that means there is something wrong with the "start" circuit.(brown wire)

Before you start testing, you can remove the yellow wire from the starter relay.  That will keep the starter from cranking while you test. 

Have someone hold the key to the "start" position. With a test light, probe the brown wire at the base of the steering column.  Test both sides of the flat connector and make sure power is going through that plug.  That plug is notorious for having loose connections.  If that's good, move to the bulkhead connector.  Check for power on the brown wire on both sides of the bulkhead.  If that's good move to the ballast.  The brown wire connects to the blue wire at the ballast.  Make sure you have power there during "start".   

Somewhere you are loosing power on the brown wire.  Once you let off the key, power transfers to the blue wire and it starts.

[Chryco Psycho]

 

[Dodgem Doug]

I checked all my terminals on the brown wire from the ignition switch back through the fire wall  to the ballast resistor for the 12 volts. Everything checks out good. I tried starting it after everything was put back in place and had the same issue. I had to hook the battery charger up cause I was running low and with the charger hooked up on low amperage the car started right up.

I disconnected the charger and got the same ole cranking till I let off the key, it started. I must be dropping voltage during cranking. The starter is new and turns the motor over good. Battery Cables? They are new aftermarkets.

Any suggestions would be appreciated.

[nsmall]

Dont get mad.  You will get this figured out.  I cant think of any suggestions besides making sure you have good solid grounds and checking for any loose wires.  I recently had a loose wire that connects to the bottom of the bulkhead that was loose that prevented my car from starting.  Is it possible your new ignition switch is faulty?  Do you have any spares ignition parts to try?  Good luck, I know this can get annoying fast.

[Matt13]

I had a similar problem with my 1973 Barracuda. Cranks and cranks, but only starts after I stop turning the key. Turned out to be a bad ignition switch; the one in the steering column that's a bitch to change!

[Bullitt-]

Burdar's advice is solid. Somewhere from the ignition switch to the coil you are loosing power on the Brown wire.  A poor connection, a poorly crimped terminal or even a wire that's broken internally can still have enough continuity to show voltage yet not allow enough amperage to start..  Careful inspection of all connectors/terminals/wiring where the Brown wire runs should reveal the issue.  Lastly the ignition switch itself could be the issue.   

[Dodgem Doug]

As previously stated, I had 12 volts through out the ignition switch, fuse block through the fire wall to the ballast resistor when cranking to start on the brown wire.

  I verified the resistance on the coil and it was good. I pulled the cap off the distributor to check the pickup/reluctor. I did make a small adjustment to the gap which calls for .010". I also again check the resistance on the distributor pickup. After everything was put back in place we have fire when starting!!!

I can't pin point the actual problem because I was checking a lot of things between trying to start the car. I just hope it's a permanent fix. I think now it's beer thirty!!!

Thanks everyone for your input and suggestions. 

[dvs cycles]

Are the plugs new also?

[dodj]

I pulled the cap off the distributor to check the pickup/reluctor. I did make a small adjustment to the gap which calls for .010".

Glad you got it running. Just FYI, chrysler distributor reluctor gap is supposed to be 0.008

[Dodgem Doug]

All new plugs & wires.

[nsmall]

I like those headers and thanks for the update.  I'm glad to hear you got it running now go get that engine dirty.