1968 Chevrolet Chevelle Voltage ot ignition coil

JOEYMU

MEMBER
1968 CHEVROLET CHEVELLE
6.5L
V8
RWD
AUTOMATIC
80,000 MILES

We had trouble getting the vehicle to start. I found that I had zero volts on the positive terminal of the coil. I disconnected it and supplied 12 volts directly to the coil. The cat started and runs fine. With the wire from the ignition switch disconnected from the coil, it has 12 volts on it. When I touch it to the coil, the voltage goes to zero. I have replaced the coil and get the same readings. The coil that was in it (not sure it was original) said that it had to have a resistance in the line. Thought that might be the problem, but cannot find a resistor. Is it possible that this model has a resistive wire, but if that is so, why would the voltage drop to zero with the new coil. What is the original configuration (is there supposed to be a resistor and a coil requiring such? If so, how do I find the wire or do I have to get a replacement and if so where? Would it be best to install the new coil that does not need the resistance and connect it directly to a 12 volt source?

4 Replies

CADIEMAN

MECHANIC
3,544 POSTS

Find a wire wih voltage with the key on at the ignition switch. Splice another wire from the ignition swich to the postive side of the coil. Is it ok then?

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Thursday, May 7th, 2015 AT 11:32 AM

CJ MEDEVAC

MECHANIC
11,005 POSTS

DIFFERENT FELLER

GOT A LOT FOR YOU TO DIGEST OFF OF A COUPLE OF PLATES

I'M SORTA "DIFFERENT" IN MY APPROACH TO TEACH STUFF, YOU'LL PROBABLY THINK I'M CRAZY AS YOU READ MY POSTS

WE'RE LOOKING AT A FEW POSSIBILITIES, IF THE POINT'S ARE CLOSED WHEN THE ENGINE STOPS, GUESS WHAT?.,.,..,.,.,.,.,.,.,THE SYSTEM IS GROUNDED, YOU WILL GET NO VOLTAGE AT THE POSITIVE SIDE OF THE COIL.,.,.,.,.,.,.,.KINDA HOW THIS ALL WORKS!

PLEASE SEE THIS LINK, I HAVE A WIRE DIAGRAM IN THERE THAT MIGHT SHED LIGHT ON SOMETHING, EVEN THOUGH IT'S ABOUT MY JEEP, 'MEMBER, SOME OF THESE 'LECTRIC VALUES MAY BE SPECIFIC TO MY JEEP AND NOT YOURS

http://www.2carpros.com/questions/points-burning

2ND COURSE

http://www.2carpros.com/questions/1970-jeep-cj5-ignition-issues/page/2

3RD COURSE

SEE PIC BELOW, GOTTA KNOW "WHAT KINDA COIL YOU HAVE" DOES IT NEED EXTERNAL RESISTANCE? DOES IT HAVE INTERNAL RESISTANCE? (NO NEED FOR EXTERNAL RESISTANCE)

MAYBE WE HAVE A DIFFERENT PROBLEM, LIKE SOMETHING MIS-WIRED?

I MAY CAN OFFER SOME "BASIC" TESTING ON SOME OF YOUR STUFF, SHOULD MY "LINKING" NOT HAVE AIDED YOU

RETURN WITH A GRIN

OR

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THE MEDIC

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Thursday, May 7th, 2015 AT 7:01 PM

JOEYMU

MEMBER
1 POST

You get a grin. Just got a chance to work on the Chevelle this past weekend and we had fun. I direct wired the positive terminal to the ignition switch and everything works like it is supposed to - at least for the casual user. The car is running like a champ.
However, I have two questions. As I understand it the resistance wire is in there for the purpose of reducing the voltage on the positive terminal to nine volts ( I still get zero) to keep from burning up the points over time. The way I have it wired it gets 12 volts all the time. Do you think this is a problem?
Secondly, on this chevelle, it is supposed to get the 12 volts when starting from the starter solinoid. The starter solinoid seems to work fine, but I do not believe it is delivering the 12 volts. Since the starter solinoid is in hard place to reach, I tested to see if this is the problem by hooking up the wire with the resistance, applying 12 volts to get it started and figured if that was the problem the car would keep running when I got it running and took the 12 volts away. It did not. So it is obviously not getting power through the resistance wire. Any ideas? Should I just be happy that I have a car that is running super today?
Thanks for your help.
Ed

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Wednesday, May 27th, 2015 AT 12:42 PM

CJ MEDEVAC

MECHANIC
11,005 POSTS

I COULD NOT FIND OUT IF YOUR RIG HAD A COIL WITH A BUILT IN RESISTOR (CHECK WITH A COUPLE OF PARTS STORES)

EVEN BETTER DOES THE ONE YOU HAVE (FROM WHERE EVER HAVE ONE?)

WE ARE LOOKING FOR ONLY ONE RESISTANCE IN THE SYSTEM (NOT THE WIRE AND A RESISTOR COIL)

IF YOU HAVE/ HAD A RESISTANCE WIRE, IT MAY BE SHORT, MEANING THE RESISTOR WIRE MAY GO (LETS SAY) 3 FEET AND TIE INTO A SPLICE (WHICH IS PROVIDING 12 VOLTS FROM THE IGNITION SWITCH)

YOU MAY HAVE TO FOLLOW "WHAT YOU THINK" IS THE RESISTANCE WIRE, LOOK FOR BREAKS, IF YOU COME ACROSS A BALLAST RESISTOR, IT'S COIL MAY BE FRIED

I ALSO LOOKED UP TO SEE IF THERE WAS A BALLAST RESISTOR ON THAT VEHICLE (DOES THE SAME JOB AS A RESISTOR WIRE) NO DEFINITE YES OR NO

BELOW PICS

1) THE WAY A '79 CJ-5 IS SET UP/ SEE RECTANGLE IN THE MIDDLE

2) MINE IS A '77 (IT DID NOT HAVE A RESISTOR WIRE), I UPGRADED TO A '79 SYSTEM, I ADDED A BALLAST RESISTOR (SO EVERYTHING ELSE COULD REMAIN '79 IF/ WHEN I NEEDED PARTS AT A PARTS STORE-LESS CONFUSION WHEN YOU SAY I NEED A COIL FOR A '79)

3) YOUR SOLENOID

4) I FEEL SURE THE "BOOST 12 VOLTS" SORTA WORK THE SAME AS MY JEEP, MY JEEP SET UP (JUST LIKE A FORD)

GLAD TO SEE YOU RETURN

I HOPE I HAVE BEEN HELPFUL

IF I FAIL(ED) TO ANSWER A QUESTION -SHOOT AGAIN!

'NUTHER GRIN?

THE MEDIC

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