73 DUSTER ELECTRICAL PROBLEMS
 

First let me explain how this started. 73 340 duster with msd 6al ignition and stock distributor. Car has been running great for 8 months. Started it and drove to town. Turned it off. Went to restart and wouldn't turn over. Jumped relay with a screw driver and it started. Went and bought a relay. Car would crank but had no spark. Cross relay with screw driver and it has spark. Use the key and it has no spark. Put old relay on and it would crank with old relay but no spark. No matter which relay you use it will only fire the ignition by crossing the relay. Starter cranks the same speed whether crossing relay or using switch. I know that msd ignitions wont start on less than 12 volts so i checked. Only getting 10.5 to the box. Put an ignition switch in it with same results. Every wire that is hot 24/7 has 12.5 volts. Every wire that gets hot with the ignition turned on has about 11 volts. I am looking for any info I can get. Thanks in advance.

the ballast resister is supposed to reduce running voltage while the key is in the run position, that's why you're getting full voltage while cranking. a separate lead applies full voltage when cranking?

what is the voltage at the coil when the key is in the run position?
what is the voltage at the coil when the key is in the start position?

When the key is on there is 10.5 volts going to the msd but nothing going to the coil. But for some reason it will still start when you cross the relay. Also when the key is on there is only 11 volts going into the resistor and 11 volts coming out of the resistor. I wired the msd to the wire that feeds the resistor.

i'm still scratching my head on this one!

on the relay i think you have:
1 cable from the battery
1 cable to the starter
1 wire to activate the relay
1 wire from the neutral safety switch

are there any other wires connected there?
is the white wire on the msd getting power when you crank using the key?

I have been scratching my head too. You are correct on the wires on the relay. The white wire is only getting 10.5 volts with the key on. I have not checked it while cranking due to lack of help. The wire going to the ballast drops to 0.5 when you crank with the switch.

i'm getting confused. i'll repost in a bit. i said something wrong

ok, the duster uses two feeds for the control box, one goes through the resistor, the other goes direct when cranking. i think you have the + feed to the msd box on the line that comes from the ign. switch when running. (which you said drops off when cranking)

does your resistor have 2 pins or 4?

Help HOPEFULLY is on the way !!

Hi guys ,Im new to this site. i thought id put my 2 cents in. Ok when you cross the relay terminals, all your basically doing is by passing the ign. switch and the key. A buddy w/ a 70 charger had the same deal happen to him the other day. wouldnt start , cross the terminals bang. if you pull all the connectors from the bulk head connector and then pull the bulk head from the inside, i bet youll find so much corrosion on the inside of the female ends that you arent getting a good conection. if so puta teaspoon of arm and hammer baking soda in a aliminum pie pan w/ 1/2 deep water, put the whole bulkhead fitting face down in it.let it fizz up for like 4 min. if it doesnt fiz add more soda. pull it out then from the back side of the bulk head fitting blow air w/ gun to totally dry it out or use heat gun on low setting to dry it out. then use a tooth pick, put a small amount of vaseline on all the terminalsto seal them from corrosion and put it all back together , my buddy did this and the car fires everytime now. no prob. I hope that thi helps and is the prob.

The resistor I have is four pin. My white wire is connected to the wire that feeds the ballast and my red power wire is on the hot wire on the alternator. It has been running great for 8 months like this. So i am thinking that something has broken down. Maybe I need to look at the plug on the firewall.

with the red wire on the alternator, wouldn't the msd be powered all the time?
do you have voltage on both sides of each resistor when cranking? a test light test would be ok. it sounds a lot like one side of the ballast resistor is burnt out. this is easily tested by bridging the resistor with a jumper wire.

Ok. First I just looked and the white wire is not used on my car. I cut that off during installation. MSD said to. Second the box has two powers. One is powered all the time. It goes to the alternator. It is a 10 gauge red wire. The other one is what triggers the box to start working. That is the one going to the ballast. It is a 16 gauge red wire. The ballast does have voltage on both sides. Also the wire triggering the ignition is connected before the balast so it shouldn't lose any power from the balast. Also just tried cleaning the master connector on the firewall with no results. I have searched all the wires and found a ground that was worn through and fixed that with no results. I can't find a wire anywhere that is burnt or worn. Do you think a bad ballast could rob the volts from the system while cranking?

did you pull the bulk head plug and look at the back side of the plug? corrosion can build on the back side as well. thats where teh connection break was at on my buddys car.

Hey. I figured it out. Thanks everybody. It was the ballast resistor. It wasn't affecting my msd at all. The bottom two pins weren't connecting. There is a wire that is in the old ignition plug that is connected. I guess it goes to the distributor but it is taped up and I don't wanna untape it. I jumpered the wires together just like you said and it fired right up. I can't believe I was scratching my head for so long over something so simple. Is there anyway to just bypass that resistor since I have an msd or do I have to use it? Thanks alot richinny.

http://www.msdignition.com/instructi...ducts/6420.pdf

you'll find a diagram on page 8 for the resistor. now i can fix that bald spot i rubbed in my head ;-)

glad i could help!

On connector corrosion issues ? ... what is the best way to handle then ?

Thanks for the link richinny. As for doc. Unplug the connector. Take a small knife and scrape any heavy corrosion off the male and female ends. Be careful not to bend or break them. Then take some good electrical contact cleaner and clean them up. Then all thats left is putting some good dielectric grease on the ends and plugging them in.

B-guy ... no sand paper or wire brush needed? ..what is the best way you have found to get inside the female end? Or just doesn't it matter - with using the grease?

If you have a real thin file that works, but I just use a small flat head screwdriver. You aren't trying to get it all out just get the main bit of corrosion out. Then the electrical cleaner should take care of the rest. Believe it or not Tuff Stuff actually will dissolve a lot of corrosion. I use it on batteries all the time.