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  #1  
Old 09-18-2014, 02:13 PM
tattooboy37 tattooboy37 is offline
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Default Coil Test Fine, NO SPARK @ PLUGS

Hey everyone, I am having problems getting my '63 w/ 390 started. I got it started a week ago after it had sat for 5 months or so just by adding gas to carb. only took a couple cranks and it ran fine. Now I cant get spark to the plugs. It has an electric ignition and has always worked fine. I tested the coil and got what seemed to be ok readings for primary 1.6 ohms and secondary 10.7 I also replaced the condenser not too long ago. It seemed fine too when I put my multimeter on each end the reading steadily declined. I also tested the lead from coil to distributor. It had a resistance of 4.72 by itself and was reading 15.35 attached to coil/unplugged from dist. If I subtract the 4.72 from 15.35 you get 10.63 which is really close to 10.7 (reading of 2ndary coil). I have a spark plug tester light inserted between plug wire and plug and am getting nothing. I tried the old way too by pulling lead from coil to dist. and tried cranking it over and got no arc/spark there either. this has me confused as why reading seem ok but no spark when I hold it close to the cylinder head and crank engine. Does the reading of 4.72 seem high for just the wire itself?

Is something fried or going on in distributor cap. I don't know terminology for inside the dist. cap but there is a small nub in the center below where the coil wire comes in, it appears a bit dirty, but overall seems fine. Also the rotor has a metal tab mounted on top to contact that nub which also seems fine (only a small black dot from contact point).

Any ideas on what or how I can check dist. cap because everything leading to that point seems fine to me, but of course I could be overlooking something simple like the high tension lead. Shop manual says if the spark is good at high tension lead then the problem is probably in the cap or rotor. So why do I get an ok reading on the meter for the lead wire but no spark when cranking.

Manual also says if there is no spark at high tension lead than problem is most likely in the primary circuit (not sure what they are referring to) , bad lead (seemed to test ok) or coil (seemed to test ok). So what is the PRIMARY CIRCUIT?

Thanks in advance and sorry for such a long post
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  #2  
Old 09-18-2014, 04:20 PM
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jopizz jopizz is offline
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In order for your coil to put out voltage it must get 12V from the solenoid when the engine is cranked. There's nothing in your post that showed that you did any voltage tests in addition to the ohms tests.

John
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Old 09-18-2014, 04:40 PM
Yadkin Yadkin is offline
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Coil + gets 12v from the starter solenoid when cranking then 5v from ignition circuit resistor wire when running. Coil - is turned on and off by the distributor points or electronics. Install a jumper wire from the battery positive to the coil + to test that circuit.
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Old 09-18-2014, 09:54 PM
tattooboy37 tattooboy37 is offline
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Quote:
Originally Posted by Yadkin View Post
Coil + gets 12v from the starter solenoid when cranking then 5v from ignition circuit resistor wire when running. Coil - is turned on and off by the distributor points or electronics. Install a jumper wire from the battery positive to the coil + to test that circuit.
Thanks for the help. I just want to make sure I understand correctly. I need to hook up a jumper wire and then crank engine or take a reading somehow? Obviously if I crank it and it sparks its a bad solenoid?. Is this just by-passing the solenoid?

How do I do voltage test as recommended by jopizz or is that being done by by-passing solenoid?

thanks again guys
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  #5  
Old 09-18-2014, 10:14 PM
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Quote:
Originally Posted by tattooboy37 View Post
How do I do voltage test as recommended by jopizz or is that being done by by-passing solenoid?

thanks again guys
Put a voltmeter on the + terminal of the coil. Crank the engine. If you get 12V then the solenoid is good. If not then the solenoid is bad or the wire is bad. Putting a jumper from the solenoid to the coil and seeing if you get spark when you crank it will accomplish the same thing.

John
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Old 09-18-2014, 10:30 PM
tattooboy37 tattooboy37 is offline
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Thanks again guys. I just went out to do a solenoid check that I watched online. he said to check by putting the meters ground to top of solenoid and other lead to the starter side post of solenoid and crank engine. I have a bump starter so I hooked it up and when I had the meter attached it started right up on the first try. Did the meter somehow help to make a connection or was it random?

Tried to turn over a second time w/ the key and it didn't start.
Did test recommended below by jopizz. I grounded meter to engine block and put + lead to + side of coil. cranked motor and it started again.
Tried it a third time w/ just the bump starter and no meter attached and it wouldn't start again.

I'm starting to think maybe something must not be grounded correctly. if the starter was bad it wouldn't crank at all right? It seems each time it does start I can hear the distinctive sound the starter makes as it disengages. all of the other times the fan/belts all turn when cranked but not that noise. just throwing everything out there so you guys have better understanding.

Last edited by tattooboy37 : 09-18-2014 at 10:51 PM.
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Old 09-18-2014, 10:52 PM
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Hooking the meter up the way you did would have no effect on sending 12V to the coil. There are two parts to the solenoid. The first part sends 12V to the starter(large post), the second part sends 12V to the coil(small post). Since your car always cranked the first part of the solenoid was always good. It was probably just random that it fired. Solenoids are known to be flaky at times.

You could certainly have a ground problem. There should be a ground strap from the engine to the firewall. It's normally bolted to the rear of the passenger side head. If that's not in place or not tightened down it would cause a number of electrical problems.

John
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Last edited by jopizz : 09-18-2014 at 11:10 PM.
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Old 09-18-2014, 11:09 PM
tattooboy37 tattooboy37 is offline
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Quote:
Originally Posted by jopizz View Post
Hooking the meter up the way you did would have no effect on sending 12V to the coil. There are two parts to the solenoid. The first part sends 12V to the starter(large post), the second part sends 12V to the coil(small post). Since your car always cranked the first part of the solenoid was always good. It was probably just random that it fired. Solenoids are known to be flaky at times.

John
I guess I'll just replace the solenoid since they are cheap enough. Then I'll know for sure if that's it. Thanks for your help John
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Old 09-18-2014, 11:12 PM
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I edited my post after you mentioned a possible ground problem. I would check that your ground strap is connected and tight.

John
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  #10  
Old 09-19-2014, 01:15 PM
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Quote:
Originally Posted by tattooboy37 View Post
...So what is the PRIMARY CIRCUIT?...
The ignition coil is divided into two parts, as are all transformers. The low voltage side is the primary side and the high tension side is the secondary side.

Grounds are equally important in every circuit because one wire will not complete a circuit. Make sure your points have a solid ground wire connected to the pivot plate it is bolted to. If the points cannot complete the path to ground you will get no spark. Your Coil is grounded by the case. If it is rusty, clean it with a wire brush. With the points open, test your condenser to make sure it is not shorted.

The condenser should show ~.02uf if you pull it out. It is an essential part, creating a 'tank circuit' with the Coil. A weak orange-colored spark can be caused by a bad condenser, weak Coil, bad ballast resistor (or resistance wire from the Key Switch, too low voltage (possibly from a bad ballast (resistance) wire) or bad plug wires.

The wire connected between your Coil (-) negative post and the distributor Points should show NO resistance, it should be very flexible and the insulation must prevent a ground.

The Coil (+) post should have two wires on it. One comes from the resistor wire from the Key Switch, and the other goes directly to the Starter Solenoid I(gnition) post.

Multimeters are good but they give false readings because they draw NO LOAD. Use a test light. Either make one from a 12-volt device (dashboard lamp, 1156 bulb, etc.) or buy one that is not neon.

With the Key Switch on and one end of your test light on solid ground, you should find some power at the Coil (+) terminal, and the same power at your Starter Solenoid (I) terminal wire.

Do this test: Put a spare spark plug wire with a spark plug on the end, into your coil tower and lay the plug on ground. Make sure your points are open and keep the cap off to the side.

Now for the test... turn your key to 'ignition' and ground the Coil (-) neg side with a separate 'test' grounding wire. Every time you pull the wire OFF, your spark plug should show a pretty blue spark. If so, ground at the points and pull the wire off. If you have spark again, trash the test wire and short circuit the points contacts with a screwdriver. This will test for a good ground at the distributor. Again, when you pull the screwdriver away, you should get spark.

If you never get a spark but have voltage at the Coil (+) post, your Coil is bad. - Dave
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