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Electrical Problem?!?!?

somethingspecial

Well-known member
Joined
Aug 13, 2005
Messages
1,795
Well I tried to start my 68 coupe yesterday, and had no spark from the coil. I checked the lead wire from the firewall to the coil and found it only had about 1-2 amps fluxuating. If I hot wired the coil from the battery, it would fire. I can't seem to find the problem why the voltage is so low. Any Ideas. This car has not run since 1980, so I have no history on it. Rebuilt engine and trans. All original wireing. Wireing looks good. No chop jobs under the dash. All other systems seem to work fine with 12 volts flowing. Does the coil hot lead have a resister built in somewhere that I am missing??????????????????? Mike
 

rvrtrash

Well-known member
Joined
Apr 25, 2003
Messages
3,649
Mike, your coil actually receives 2 different voltages at different times. Here's a "quick" explanation and maybe that will help you. When you turn your key to "Start", the solenoid energizes and puts 12V on the small term closer to the starter cable. That wire goes to the coil to give it a "kick" for starting. Once the engine starts and you release the key to the Run position, the starter solenoid disengages, the 12V goes away and the Ign. switch provides voltage through a resistance wire to the coil. You will read about 9V at the coil while the Ign. switch is in this position. If the car has been sitting that long, I would buy some electrical contact cleaner and clean all your connections, including the back of the Ign. switch. Then measure the voltage at the connection on the solenoid while someone cranks the engine briefly. You may have a solenoid that has an internal connection oxidized and need to replace the solenoid. If that is good and it still won't start, check the voltage at the coil while someone cranks it. It should read 12V and then drop to 9 when they release the key to the run position. When you get that far, if it still doesn't run, PM me and we'll work further.

Steve
 

Midnight Special

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Joined
Nov 5, 2005
Messages
3,713
Location
Grass Valley, California
...Mike, I just replace a solenoid that did the exact same thing. Before it quit altogether - there was a hesitation from the time I turned the key to when the engine began to crank. When it quit - it cranked with no spark on the points, dist. and coil. Steve - my brother in law explained it just as you did!
 
OP
OP
somethingspecial

somethingspecial

Well-known member
Joined
Aug 13, 2005
Messages
1,795
I get the BONE HEAD AWARD for the day.

I had the Temp. sending unit wire and the coil wire reversed. I switched them out and it fired immediately. Sounds great and all systems are working. Thanks for all your help. Mike
 

robert campbell

Well-known member
Joined
Apr 10, 2007
Messages
4,321
Steve is right on as usual!! I have had the opposite problem more often. When the key is in the start position and cranking the starter, the car fires and runs. Once you release (let go) of the key and the key switch returns to the "run" position, the engine would die and you had nothing at the coil.

Do what Steve says and soak the ignition switch in wd-40 or your favorite. Disconnect the battery and cycle the ignition switch a bunch of times. Until you fingers get tired.... Nothing to lose. If the switch key switch is bad, then Steve or I can step you through the tumbler removal steps to get the switch out. Still available at most part stores.

Rob
 

robert campbell

Well-known member
Joined
Apr 10, 2007
Messages
4,321
I have held a wrench in my left hand and searched all over the garage with my right hand before.......

Think I will start a thread for "best bone-head awards"! I got a bunch that will certainly rank right up there!

I bet Steve has a few....

We can vote!
 

CougarCJ

Well-known member
Joined
Jul 17, 2006
Messages
2,186
I had the Temp. sending unit wire and the coil wire reversed. I switched them out and it fired immediately. Sounds great and all systems are working. Thanks for all your help. Mike

I almost suggested that, but figured the car ran previously.

I got a reproduction engine gauge feed wiring harness from ??? It turned out that when they were reproduced, they switched the wire color between those two items. I had to trace the wires from the 3 hole plug and figured it out.
 
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