The Dodge Challenger Message Board

My 70 challenger won't start while it's cranking over. If I have my foot on the gas lightly, the car starts as soon as I release the key. I've replaced the ballast resistor per a friend's reccomendation. The module seems/looks fine- no burn marks or anything out of the ordinary. I remember reading something about this in the past, but can't remember what the fix was. Can anyone offer some insight? Thanks.

I am having the exact same problem with my 70. I am anxious for a cure.
Bob

Does it do this when warm or hot? It sounds like it's an electrical issue,(fusible link form Batt positive to starter relay), If not, I would check my choke opening or closing position if it's hooked up.

Looks like you don't have ignition while in the start position.
Mopars get ignition through 2 different paths :
- when in the ON position, ignition power is routed through the ballast resistor. That power is not available in the START position.
- when in the START position, ignition power bypasses the ballast resistor.

Your problem does not come from the ballast resistor (the engine would start when cranking, and would die when you release the key).
Something is wrong somewhere between the ignition switch and the coil side of the ballast resistor.
Since you can crank the engine, the problem probably lies at or close to the ballast resistor terminal.
I would do the following :
- disconnect the starter from the start relay
- have someone turn the key to the START position.
- Check the brown wire that goes from the bulkhead connector to the ballast resistor. It should have battery power (use a voltmeter, or a small lamp). If it doesn't, check the connection at the bulkhead. If you don't get 12V there, trace that wire inside and check under the dash (it goes straight to the ignition switch, still brown). The ignition switch has the following wires, in that order :
- Red
- Red
- Orange
- Red
- Brown (START ignition power)
- Dark Blue with tracer (ON ignition power)
- Black
- Yellow (starter relay activation)


I used to have an intermittent problem like this one on my convertible, it was the brown wire that was touching the exhaust manifold...

Just to add to this. When I fitted my painless wiring harness I realised that their instructions and wiring only give you the brown (start) wire so if I had tried to start the car it would have cut out every time I released the key (the opposite problem to what you have).

we had this problem with an aussie charger years ago it turned out to be the starter was the problem we put another starter in & problem solved , if you have a spare give it a try
cheers ian

I would check the battery and/or the ignition coil.

Did you know that the voltage drop during cranking on a 100% fresch battery is at least 2-3 Volts? If the battery gives 12V uninfluenced, then during cranking it only gives 9-10 Volts!!! A knowledgeable friend told me this just the other day. A bad battery can have a whopping 5V voltage drop, leaving only 7 Volts for the other components. Since the ignition coil acts a voltage multiplier, this low voltage makes the job quite tough for the ignition coil.

I think it is a very good idea to step up in battery size on a car like a Challenger. I believe that a 60Ah battery is not sturdy enough. I think a 70Ah battery (or bigger) will cope with the job much better.

You're friend is right Chris. Here is a diagram which can help explain it a bit better than I. A Battery load test would only take minutes to perform. You can also test the coil primary and secondary resistances. The primary should be around .5 to 1.5 Ohms the secondary around 10k ohms with a factory type canister coil. MSD coils will be close to this but they have a lot more secondary windings so it should be a little higher on the secondary, as long as it's not infinite the coil should be OK. You can also test across the ballast resistor, it should be close to .5 to 1 ohm I believe. The ballast is not in the circuit during Crank, only during run. I have been jumping back and forth from Milliamp circuits on my project to voltages on the old stuff. Please correct if wrong guys.

christer wrote:I would check the battery and/or the ignition coil.

Did you know that the voltage drop during cranking on a 100% fresch battery is at least 2-3 Volts? If the battery gives 12V uninfluenced, then during cranking it only gives 9-10 Volts!!!

That's the reason for the ballast resistor, and the reason it's bypassed during cranking. The coil is designed to work at 9-10V max.

I've got the same problem Dave does, with the MSD Box. I had to wire a separate 'ignition' switch to power the box. I hate it. I'll replace that with a pair of diodes as soon as I can.