408 wont run

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moparspares

moparspares

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My 408 I built ran beautiful on the engine stand and now I have it in the car it wont start. When I turn key it starts momentarily albeit very rough then dies. It's not a fuel problem as I can see the carb has plenty of fuel.

I feel it is an electrical problem. At first I thought it was a lead mixed up or dist in 180 degrees out but I have checked them a couple of times and is correct. I have a MSD Digital E curve which I have locked out, dials set to 0 0. All the original electronic ign has been disabled and dist is wired to MSD recommendations. Any ideas?
 
moparspares said:
My 408 I built ran beautiful on the engine stand and now I have it in the car it wont start. When I turn key it starts momentarily albeit very rough then dies. It's not a fuel problem as I can see the carb has plenty of fuel.

I feel it is an electrical problem. At first I thought it was a lead mixed up or dist in 180 degrees out but I have checked them a couple of times and is correct. I have a MSD Digital E curve which I have locked out, dials set to 0 0. All the original electronic ign has been disabled and dist is wired to MSD recommendations. Any ideas?
Click to expand...
Have you double checked your firing order?
 
sure it isn't a vac leak? almost sounds like when you have the big vac off the back of the carb..
 
If it ran on a stand it should run in car. If you didn't remove any parts to get it in. I would check your wiring. Does it only want to run with the key in the start position?
 
I would retrace my steps from run stand to car. Did you test it on the stand with your MSD ? Power at the coil with the key in run after engine dies ?
I don't know what the 0-0 means. if it ran fine on the run stand then look into what changed when put into the car.
 
Yes it feels like it only wants to run with key in start position. When I let go of key it just dies. I am going to start from scratch. Pull distributor, leads and start from scratch installing dist and leads. Check all the wiring to the MSD and make sure im getting a full 12 volts at coil. It must be something simple i have missed.
 
You need 12 volts at the coil when the switch it is at start and went the switch is at run.....you can run a jumper wire straight from the battery to the coil and see if it fires and run...
 
I won't pull the distributor unless you not sure it in right. Check the wire you getting 12v from. Make sure it's has 12 all the time the key is on. Or find the two wire that feed the ignition and put the on the coil.
 
70aarcuda said:
You need 12 volts at the coil when the switch it is at start and went the switch is at run.....you can run a jumper wire straight from the battery to the coil and see if it fires and run...
Click to expand...
Tony ,stated it.... 12 volt it,on a jumper wire.. Don't over think it,one step of diagnosis,at a time...
 
Retroboy said:
Your description of the fault is exactly the same as a faulty balast resister. Cheers Tony
Click to expand...
or perhaps were talking about a car that came with a points distributor and now hes trying to run an electronic ignition and never bypassed the ballast
 
i had the same problem when i wired a 6al into my car.
i had to wire together two wires so i got 12v to the msd during the start position and the run position of the ign switch.
you could find the two wires at the ballast resistor or you could wire it up right at the bulkhead...which is what i did since the previous owner did some pretty ratty wiring to install an electronic ignition.

find ign1 and ign2 on a wiring schematic...
 
Ok
I went through everything again and it was all correct. Fired and nothing so I used the hot wire from +battery to coil + and success. Fired right up. I have taken a photo of the wires at ballast. Now of course these are just sitting on the ballast - THEY WERE NOT HOOKED UP WHEN STARTED as the MSD does not need a ballast resistor. Next question is which wires here do I join together to make it work. Please make it simple as electrical is not my strong suit.
 
Sorry heres the pics

WARD5459.JPG


WARD5460.JPG


WARD5461.JPG
 
looks like you can eliminate the dark blue wit all together, then connect the light blue (which should be hot in run) to both browns and the green/red
(you are feeding all of them with the blue one)

or...if you want it to look real spiffy, remove the ballast resistor from the firewall and gut it from the back
once the space connectors are exposed, solder jumper wires in place of the resistors and bolt it back on

that way it will even look stock

(it was a little easier with my 2 prong resistor)
 
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Take your volt meter out and find the wire that has 12 volts when the key is in run, then trace the wire that comes from coil positive and couple them together. I'm more familiar with the 2 post ballast as well but if you look at the wiring diagram for your car it should be cut and dried. Start feeds 12 volts to the coil and run goes through the ballast . Check out the wiring diagrams
 
iw378 said:
Take your volt meter out and find the wire that has 12 volts when the key is in run, then trace the wire that comes from coil positive and couple them together. I'm more familiar with the 2 post ballast as well but if you look at the wiring diagram for your car it should be cut and dried. Start feeds 12 volts to the coil and run goes through the ballast . Check out the wiring diagrams
Click to expand...
Put it in run then probe each side of the ballast for voltage readings
 
iw378 said:
Take your volt meter out and find the wire that has 12 volts when the key is in run, then trace the wire that comes from coil positive and couple them together. I'm more familiar with the 2 post ballast as well but if you look at the wiring diagram for your car it should be cut and dried. Start feeds 12 volts to the coil and run goes through the ballast . Check out the wiring diagrams
Click to expand...
 
I just put a MSD setup in my 69 points dart. Real simple, find any wire that has 12v with the switch on and connect to small red wire on msd take stock wires off the coil and run the orange wire from the msd to coil pos black from msd to coil neg. big red from msd to batt, big black to grd. plug msd plug to dist. U can leave the rest of that crap hooked U just bypassed all or it.
 
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