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Voltage at Coil Positive Ralph 7-29-02  
1978 Dodge 440 with electronic ignition. What should be the voltage at the coil positive terminal with the ignition switch on? A Chiltons repair manual says 12volts, a troubleshooting guide I have 5-7volts. I am reading 5.5 volts. Thanks in anticipation.
Re: Voltage at Coil Positive Joe 7-29-02  
The 5.7 is in the "Run" position, While 12 volts in the "Start" position. There is a white ceramic ballast resistor that reduces voltage in the run position. These frequently go bad on Dodges. Check the voltage on the ballast and see if you have 12 volts on one side and 5.5 or 5.7 on the other side. Remove the wire on the coil "Hot" side and see if the voltage changes. Is this giving you a problem?
Re: Voltage at Coil Positive Joe 7-31-02  
I'm going to make a suggestion to you. Wait until a super dark night and start the engine to see where the spark may be jumping. It could be jumping through a high tension lead or leads to the wire leading from the ignition switch. Check for a bad ground. Check your distributer cap. Joe
Re: Voltage at Coil Positive Ralph 7-30-02  
Joe, Thanks for the reply. The vehicle is a 1978 Dodge Sportsman van with the Motor Home chasis. It is misfiring so badly that I had to have it towed. Timing lite confirms all cylinders are misfiring. It runs but backfires and there is no power. Substitute coil and ECU make no difference. Voltage at coil positive is 5.5 Volts with the ignition on prior to starting. Timing is OK and distributor is relatively new. When running I was receiving HT voltage shocks through the ignition key which must be a good clue to the problem. Do you know where the ballast resistor might be located? I am planning to replace the ignition wires anyway. Ralph
Re: Voltage at Coil Positive Joe 7-30-02  
Yours should be mounted on the firewall, outside under the hood, but I have seen them mounted on the rear of the engine. It will have two or four wires on it.
Re: Voltage at Coil Positive Sam Watson 7-30-02  
5.5 volts is pretty low, cosidering that the primary resistance is.5 to.6 ohm for a thermal resister, or 1.1 to 1.3 ohms for a non-thermal resister. That means you should see about 1.5 to 2 volts less than battery voltage at the coil's + terminal when key is in "run" position. Believe it or not, these ignitions will run, using just the 4.75 to 5.75 ohm auxillary side of the dual ballast resister, however, since the coil is a step-up, pulse transfomer, less voltage in means less voltage out. The fact that you were getting a HV discharge back through the wiring to the ign. switch indicates that this is what took place. A ChryCo vehicle with a dual resister unit and a bad primary side of the resister will fire when cranking because the resister is being by-passed, then runs on the aux. side when the key is in the "run" position. On the earlier point ignition vehicles it was pretty obvious, they would fire in crank, but die when the key was released.
HELP ! Re: Voltage at Coil Positive Ralph 7-31-02  
Thanks Sam, Have replaced the ballast dual resistor. However there is no change in symptoms. Still runs but misfires badly giving HV shocks thru ignition key. Rechecked voltages at coil with key in run position. 7.5V at positive and 1.5V at negative. Any further possibilities you can think of. Ralph
Re: Voltage at Coil Positive Ralph 7-31-02  
Joe, Have done the night check,and replaced the distributor cap. I also received a shock from the carb: The HT lead from the coil to the distributor has been replaced. Substitute coil made no difference. As all plugs are misfiring you would think there must be a HT short to ground between the coil and the distibuter but I can not find it. Which check for ground were you referring to? I am baffled.
Re: Voltage at Coil Positive Joe 7-31-02  
Look for any broken or missing grounds. Like EN
Re: Voltage at Coil Positive Joe 7-31-02  
Sorry, I got disconnected on my last message,but look for any missing, broken or corroded grounds between the body, battery, and engine. The fact you get shocked from the carb means you are missing a ground somewhere.
Re: Voltage at Coil Positive Sam Watson 8-1-02  
Joe, if I may, how about using a jumper cable between the engine and the battery negative post to see if that eliminates shock? Also, I'd suggest the following. With the key "off", disconnect the wiring plug from the control module by backing off the screw in the center of plug and removing plug from module. Measure voltage across battery terminals. Turn key to "run", measure voltage between coil+ and engine block, voltage should be no less than 1 volt below battery voltage.Next check voltage at coil -, on either terminal of coil you should read battery voltage or a max of 1 volt less. If it's more than 1 volt lower than battery voltage then you have a fault in your circuits. Start checking by reading voltage between engine block and battery plus, in all the checks, maximum allowed voltage loss below battery voltage is 1 volt. Next check between battery + and surface of control module---scrape a little paint if need be. Come back with what you find.
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