car starts then immediately stops....HELP
 

engines a rebuilt 360 just had the carburetor rebuilt, and it normally drives unbelieable well. Today was the first day i tried to start it in a week and as soon as the engine starts it stops. It fires right up but then dies just as fast. If i keep the key in the all the way turned position it runs but as soon as i let go of the fully turned position it stops. Im thinking its either a problem with the ignition system thinking its being turned off, or maybe the fuel pump, im really not sure though so any help would be appreciated.
thanks in advanced.

Most likely the ballast resistor is bad, if you still still have that type of ignition system in the car.

Yup. This is classic 'bad ballast.'

Here's how your Mopar starting system works You have three completely separate circuits (actually 4, the accessory switch) to make your car run

The "dark blue" is ignition "run" sometimes called "ign1". It is hot with the key in run, supplies the key (input) side of the coil ballast, the regulator, electric choke, if used, alternator field on 70/ newer, regulator, and maybe a couple of other things

When you twist the key to "start" there are TWO separate circuits in action

The normally yellow engages the starter relay if the car is in neutral/ park, if the clutch is depressed on certain cars, and engages the relay on all older stick cars

The normally brown hooks to the coil side of the ballast, and is also hot in "start." THIS IS probably what is firing your car, and when the key is released to "run" the bad ballast is not allowing power to the coil

Check the ballast, or replace, and if it's good, check for power on the "dark blue"

Thanks for replying, just replaced the ballast resistor, no luck. Same problem without any change. Any other suggestions? thanks.

As I said, check for power on the "dark blue." This is "ignition run, and comes directly from the ignition switch, through the bulkhead connector

Bad coil?

Ok, sorry I’ve taken a while to respond but I’ve been a bit busy. It would appear that whoever built my car wired it in a specific way that doesn’t exactly match the original. There’s a 2 prong ballast resistor next to the coil which I replaced, there’s also one on the drivers side that’s 4 prong which I also replaced. "The Dark Blue" wire coming from the bulk head is not connected to anything and has never been connected to anything, it’s just hanging there. Everything that is connected appears to be getting power although I have not yet opened the column up to check the connection at the ignition.

Because it’s firing perfectly I don't think it’s a coil problem but I’m not a mechanic by any means so I guess that could be it. Thinking it’s more of a wiring issue. I’m really stump here so any help would be fantastic, thanks

If the wiring has been changed from stock, it is going to be pretty difficult for us to "imagine" how it is hooked up now.

Best advice I can come up with at this point is to find someone locally who can help you

Is it possible "they" installed a relay to operate the ignition/ accessories?

Maybe try to use a temporary jumper wire from the battery to the positive side of the coil and see if it will run. If so the problem is in the wires or switch. Kinda sounding like your switch might be bad. I have done this as a theft deterant, by hiding the toggle under the dash. Still kinda sounds like the ballast. You should really get a shop manual for your car and wire it up right. Does it have the stock ignition or was an aftermarket system used? As 440rr says, Since you say the blue power wire was not used, it will be hard to diagnose on line. Do you know anyone with a little knowledge of older cars? If not try to find a local club, preferably one with some older guys that know these cars. Maybe go to a tech school and see if the teacher will be willing to use your car to teach his class.
Good Luck.

so the ignition system was updated with an accel super coil. that is when the previous owner kinda deviated from stock wiring. the ballast resistor on the driver side firewall measures the proper resistence across terminals per the factory manual. The ballast resistor near the coil measures a little over 1 ohm across the two terminals. The right side of the coil's ballast resistor is getting full battery voltage, the other side has a short jumper wire that goes to the pos. side of the coil. It gets around 8 volts when the car is running. (i can kind of wedge the ignition switch in such a way that the car will run normally and that is how i've been doing these tests) So anyway it kinda seems like the ballast resistors are doing what they are supposed to. In light of the fact that the running voltages are ok, could a bad ignition switch be the cause of this problem?

Ignition switches don't go bad very often. If the car still has the wiring going through the bulkhead connector, I'd suspect it.

(quote)
If i keep the key in the all the way turned position it runs but as soon as i let go of the fully turned position it stops.

no power in the run position of switch.

(quote)
i can kind of wedge the ignition switch in such a way that the car will run normally

This is definatley pointing to the switch. They can and do go bad. Try to bypass the switch as I mentioned earlier. Run a hot line from the battery to the coil positive side. Maybe put a toggle switch in the line so you can turn the system on and off.This will ensure the switch is, or isn't the problem. You mentioned an after market coil, how about the rest of the ignition. Is it stock, electronic, or points? If it's after market or electronic you may not even need the ballaster resister, if points , no balaster will cook the coil. A 71 has points yet right?

Start then dies.
 

If this doesn't turn out to be a ballast problem, I'll eat your Airedale.

Since this thread is several years old, I doubt that you will find out!!!!!

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