Demon won't start

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Valveguy

Valveguy

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I need some help getting my 72 Demon started. I'm not a mechanic but I'm trying to learn. Car had been running recently, battery is strong and it turns over great but won't pop off. When I was starting it this last week, it seemed like it was only wanting to start once I turned the key back, like there was a short in the key switch.

I've tried starting it without doing anything with the gas pedal and then also giving it some gas but that just makes my garage smell like gas.
 
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Sounds like an ignition problem. Please advise us what engine and what modifications have been done to it. A 72 should be an electronic ignition, not points. And with that :popcorn:
 
Woodys_Cuda said:
Sounds like an ignition problem. Please advise us what engine and what modifications have been done to it. A 72 should be an electronic ignition, not points. And with that :popcorn:
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Sorry, that was stupid to not identify the engine. It's a 340, manual transmission. Had someone work on the engine a bit several years ago so I guess I'm confusing the points part with a different vehicle. Thank you for your reply!
 
Valveguy said:
Sorry, that was stupid to not identify the engine. It's a 340, manual transmission. Had someone work on the engine a bit several years ago so I guess I'm confusing the points part with a different vehicle. Thank you for your reply!
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You're welcome, so it's most likely an ignition or electrical issue so I'll leave it to the more experienced guys here, good luck!
 
On your firewall is a dual ballast resistor, passenger side. One side feeds the ECU, the other feeds the coil. But, during cranking, power goes through both to the coil. so if one side is bad, then during cranking, the ignition does nothing, but as soon as you release the key, Bam it wants to fire. If conditions in the intake are agreeable, it will light off and you can drive away; just don't shut it off.
The proof is that when you jump 12v power to the coil positive, if it "pops off" and runs, Badaboom install a new Ballast and that's that.
Do not drive away with the power-jumper still connected; the Coil doesn't mind full battery voltage during cranking, but, on battery voltage it will run hot and eventually burn itself out. No, IDK how long is safe. It could be a mile or ten or 100, IDK.
Happy HotRodding
 
AJ/FormS said:
On your firewall is a dual ballast resistor, passenger side. One side feeds the ECU, the other feeds the coil. But, during cranking, power goes through both to the coil. so if one side is bad, then during cranking, the ignition does nothing, but as soon as you release the key, Bam it wants to fire. If conditions in the intake are agreeable, it will light off and you can drive away; just don't shut it off.
The proof is that when you jump 12v power to the coil positive, if it "pops off" and runs, Badaboom install a new Ballast and that's that.
Do not drive away with the power-jumper still connected; the Coil doesn't mind full battery voltage during cranking, but, on battery voltage it will run hot and eventually burn itself out. No, IDK how long is safe. It could be a mile or ten or 100, IDK.
Happy HotRodding
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Your info is GOLD to me AJ! Thank You So Much!!
 
AJ/FormS said:
On your firewall is a dual ballast resistor, passenger side. One side feeds the ECU, the other feeds the coil. But, during cranking, power goes through both to the coil. so if one side is bad, then during cranking, the ignition does nothing, but as soon as you release the key, Bam it wants to fire. If conditions in the intake are agreeable, it will light off and you can drive away; just don't shut it off.
The proof is that when you jump 12v power to the coil positive, if it "pops off" and runs, Badaboom install a new Ballast and that's that.
Do not drive away with the power-jumper still connected; the Coil doesn't mind full battery voltage during cranking, but, on battery voltage it will run hot and eventually burn itself out. No, IDK how long is safe. It could be a mile or ten or 100, IDK.
Happy HotRodding
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I looked under the hood of my Demon and sure enough, I could tell the dual ballast resistor was shot. It looks like it's been there since 1972, is fairly loose and I can tell that something inside of it is broken. The connective wires were allso pretty loose so I tightened them and then tried starting it. It started and ran for a few seconds so I know without a doubt about what is going on so I ordered a new one. Its supposed to be here in about a week or so. Once I get it installed, I'll try to shoot you another message. THANK YOU SO MUCH!!!
 
AJ is a pretty smart cookie!

Change the ballast resister, but I wouldn't buy a new coil just yet...unless it will make you feel better. Sometimes I do something just so I can sleep better at night!!
 
AJ/FormS said:
On your firewall is a dual ballast resistor, passenger side. One side feeds the ECU, the other feeds the coil. But, during cranking, power goes through both to the coil. so if one side is bad, then during cranking, the ignition does nothing, but as soon as you release the key, Bam it wants to fire. If conditions in the intake are agreeable, it will light off and you can drive away; just don't shut it off.
The proof is that when you jump 12v power to the coil positive, if it "pops off" and runs, Badaboom install a new Ballast and that's that.
Do not drive away with the power-jumper still connected; the Coil doesn't mind full battery voltage during cranking, but, on battery voltage it will run hot and eventually burn itself out. No, IDK how long is safe. It could be a mile or ten or 100, IDK.
Happy HotRodding
Click to expand...
I think you are on the money with this. I use to carry a spare in my old Duster!
 
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