72 demon 340 common under dash wiring issue for no start, no power

[SR77]

So i just installed bigger jets to accommodate for larger headers and when i went to start it up nothing, no lights, no cranking, nothing. I checked my battery voltage it was good, gave everything a quick visual and nothing jumped out. Threw a jump station on and just kind of left it on after trying to start it, still dead. Got under the dash and started moving around a couple of the main wire harnesses by the steering column. Just for the hell of it i pulled out the headlight switch and had head lights after i did the moving so i tried starting it and it fired up. Drove it for awhile came home turned it off and fired it back up a few more times no problem. I'd feel a lot better if i plugged something in or did something that i could actually tell made a difference .is there something common i should be looking for under the dash?

Its has a new battery, new starter, neutral safety switch.

 

[Dubob]

I'd start at the bulkhead connector. There's a red wire coming thru from the battery and a black wire that runs to alternator. The connections at the bulkhead connector are the problem area due to these two wires carrying the full electrical load of the car. These end up at the ammeter, red on one side black on the other. I don't have the schematic to give you PIN numbers but they are either 10 or 12 guage wire. That's where I'd start looking. The connector is probably melted allowing the contacts to shift around. By wiggling the harness you may have moved the connectors enough to make contact.

Download a free service manual here
http://www.forabodiesonly.com/mopar/showthread.php?t=244981

 

[70dustah]

X2 , also search MAD wiring upgrade. I did mine last year. Easy to do.

 

[gtsdude]

How did you check your battery voltage? You need a battery tester that puts a load on it when checking it.
With a meter
12.6v=100 percent charged
12.45=75
12.24=50
12.06=25
11.89=0
this is at 80 degrees outside temp

My guess is battery was almost dead, your jump box left on it long enough to charge it and it started.

 

[67Dart273]

Above posts are right. Read the MAD article, here

http://www.madelectrical.com/electricaltech/amp-gauges.shtml


You surely have damage and problems at the bulkhead connector. The diagram from the above article:

is a great overview and simplified diagram of the main primary power. Following from the starter relay, through the fuse link, ALL power into the interior goes through the red wire / fuse link and through the BULKHEAD connector.

You can buy "Packard 56" terminals used in those connectors. I got mine at 'clips and fasteners'

http://www.clipsandfasteners.com/Packard_56_Series_Male_16_14_Gauge_Terminals_GM_p/w31c030.htm

When you order the female, PAY ATTENTION, as one type they sell is wrong. Take a very very good look at your old ones, make sure the new looks exactly the same

 

[SR77]

thanks for the replies, had no issues starting it last night so i think its in the bulkhead or amp meter wiring something is loose or damaged. i just have to crawl under again and get something going.

the jump station i think was more coincidental, it was at 12.45 before i hooked it up and before i checked the acid level. the last time i had issues it was testing good voltage but i had no acid in it due to a faulty charger left on over winter.

thanks again guys for pointing me in the right direction

 

[70dustah]

The MAD wiring upgrade eliminates the issue of bulkhead connector issues for the main power circuit going though the bulkhead connector. Also I would recommend bypassing amp meter and install volt meter in its place( I think a gauge can be found for $25 ). Many great articles on it in here. I converted my amp gauge to volt gauge on ralleye dash, but there are also how to's for standard style dash.

 

[67Dart273]

The MAD wiring upgrade eliminates the issue of bulkhead connector issues for the main power circuit going though the bulkhead connector. Also I would recommend bypassing amp meter and install volt meter in its place( I think a gauge can be found for $25 ). Many great articles on it in here. I converted my amp gauge to volt gauge on ralleye dash, but there are also how to's for standard style dash.

Thanks for the reminder. Here's the thread on converting ammeter to voltmeter. My understanding, tho, is that the original "Sunpro" gauge used is no longer available. So you'll have to "re hack" LOL

http://www.forabodiesonly.com/mopar/showthread.php?t=119480

Note this thread is three pages long. Read them all, it covers different clusters

 

[gtsdude]

I hate when you can't find the actual problem, I just went thru it in my FBO ignition thread. Going to take the car out today, hope it doesn't act up again. Sounds like you might have a bad connection under dash some where, the where is the hard part lol.