72 challenger wont start

[drambo136]

Hey everyone,

So ive been building a 72 challenger original 318 that i swapped with a 1977 360. After many years I finally got it to turn over and run, it wouldnt hold an idle but its started. So the other day when I was working on the idle I noticed the brand new battery I bought was dead. I charged it up and had a volt meter attached, when I unplug the charger the battery slowly losses voltage. So I then went to try to start it again and NOTHING. Not even a single click from the starter but it does draw a lot of power still. I replaced the starter relay, checked the fuses, the ECU and voltage regulator are new, and the starter will turn if I cross the leads.

Now just a little tid bit about this car. When I bought the car it was a mess. The wiring harness is so ghetto rigged its not even funny. That being said I've looked at diagrams upon diagrams and they all seem to be different.

Any help would be appreciated

-David

[Chryco Psycho]

When you turn the key you should have power to the blue wire at the ballast & alt , in start position you should have power to the brown wire @ the ballast & the yellow wire at the star relay so check that first , if there is a power problem start checking the bulkhead connectors & the column connector at the base of the column .

[dodj]

I charged it up and had a volt meter attached, when I unplug the charger the battery slowly losses voltage.

You have a ground/parasitic drain somewhere. You need to connect an ammeter and disconnect ccts one by one to identify where the drain is. Like a door switch that keeps the interior light on or something similar.

[drambo136]

When you turn the key you should have power to the blue wire at the ballast & alt , in start position you should have power to the brown wire @ the ballast & the yellow wire at the star relay so check that first , if there is a power problem start checking the bulkhead connectors & the column connector at the base of the column .

Sorry this might be a newbie/dumb question. what ballast are you talking about?

You have a ground/parasitic drain somewhere. You need to connect an ammeter and disconnect ccts one by one to identify where the drain is. Like a door switch that keeps the interior light on or something similar.

Ya i figured itd be something like that but wasnt sure if my engine harness was so f'ed up that it was draining power somewhere

Thanks for the help guys

[Bullitt-]

Ballast resistor is the white ceramic thing on the firewall, OE on electronic ignition cars is 4-wire pictured.

[drambo136]

awww damn i knew thatd be a dumb question. Theres a 4 wire on my car right now but I do have a brand new 2 wire. Is there any advantage or is it just for a different car?

[Bullitt-]

If your car will start at all the ballast resistor is not your problem, it's a $5. part anyway so pick up a new one if in question.
Getting your car to crank sounds like the problem since you can short the terminals & it will crank the issue must be with the starter relay or wiring to it.
Yellow wire provides voltage from ignition switch in start position, brown wire provides ground from neutral safely switch on auto tranny or from clutch pedal on manual.
Issues are usually bad connections at the bulkhead connector at firewall or on the large flat connector from the steering column/ignition switch. If not getting power on the yellow wire trace it back to find disconnect. If yellow wire has power check that your getting ground through the brown wire.

[drambo136]

ok so at the on position i have 10.5v at the blue wire to the alt. and 10.4v at the blue wire to the bal. Then at the start position i have 10.3v at the brown wire to the bal and 11.75v at the yellow wire to the relay.

And Bullitt the car wont start at all, no cranking or anything.

[ShelbyDogg]

On the bullit's picture of the starter relay you see a big nut holding the positive battery cable connection. You also see the small nut holding the wire going to the starter.

Put a screwdriver across these 2 to touch them together. If your battery and starter are good, the engine will crank.

Do not do this in a manual trans car without making sure it is in NEUTRAL first.

[drambo136]

On the bullit's picture of the starter relay you see a big nut holding the positive battery cable connection. You also see the small nut holding the wire going to the starter.

Put a screwdriver across these 2 to touch them together. If your battery and starter are good, the engine will crank.

Do not do this in a manual trans car without making sure it is in NEUTRAL first.

just crossed the connection. The starter engaged but died in less than a sec

[drambo136]

if the battery is busted im gonna feel rly dumb

[ShelbyDogg]

Sorry you feel dumb, but it really sounds like a bad battery.

[drambo136]

ok replaced the battery and that didnt fix it

[Chryco Psycho]

you are losing major voltage somewhere if you have 10v in the run circuit & 12v in the start position to the starter relay . start checking connections & the base of the column & bulkhead , you should be getting battery voltage everywhere

[ShelbyDogg]

ok replaced the battery and that didnt fix it

With a good battery and good starter, when you short the relay terminals, than engine should crank till you remove the screwdriver. What do you mean it lasted less than a second? Make sure both ends of all battery cables are tight.