No spark troubleshooting
Thread Starter
Instructor
Joined: Nov 2004
Posts: 161
Likes: 4
From: Maryville TN
No spark troubleshooting
I just finished a valve job on my 65 L79 with stock points ignition and reassembled everything and attempted to start but I have no spark. When the heads were off I installed a new Lectric Limited ignition harness, everything seemed to connect properly, it cranks over just fine, but I have no spark. I did check a couple voltages, I have 12V at the + coil terminal with the key in the run position. I also have 12V at both sides of the ballast resistor with the key in the same position. The ballast resistor was changed last year. What would be the next step to troubleshoot this problem?
Le Mans Master
Joined: Feb 2014
Posts: 8,957
Likes: 5,509
From: Richardson Texas
I just finished a valve job on my 65 L79 with stock points ignition and reassembled everything and attempted to start but I have no spark. When the heads were off I installed a new Lectric Limited ignition harness, everything seemed to connect properly, it cranks over just fine, but I have no spark. I did check a couple voltages, I have 12V at the + coil terminal with the key in the run position. I also have 12V at both sides of the ballast resistor with the key in the same position. The ballast resistor was changed last year. What would be the next step to troubleshoot this problem?
Thread Starter
Instructor
Joined: Nov 2004
Posts: 161
Likes: 4
From: Maryville TN
Thread Starter
Instructor
Joined: Nov 2004
Posts: 161
Likes: 4
From: Maryville TN
I checked that wire for continuity and it is good. I also hooked a light up to the negative terminal of the coil and it flashes on and off while cranking. The plug wires are all on correct.
Melting Slicks
Joined: Aug 2004
Posts: 3,078
Likes: 101
From: Riverhead New York
Pull the Coil Wire out of your Dist. Cap and hold it near a ground while someone cranks the engine over. Spark should be a crisp Blue color. You can also watch Points while turning engine over and see if there is a spark visible. Last resort run a wire from the Battery + to the + on your coil and see if that helps. Might just be a Coil gone bad. Al W.
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Michael S. Palmer
Race Director
Joined: Apr 2005
Posts: 11,284
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From: Bowling Green, Kentucky
Pull the short coil wire out of the cap. Have a friend hold it a 1/4 inch or so away from the block/manifold when you are cranking the engine. Make sure friend uses a rag or insulated pliers
You should be getting a spark there.Perhaps the center metal "tang" on the distributor rotor is not touching the electrode in the distributor cap. You can bend it up slightly.
If you had a dwell meter, you should hook it up and check for 28-30 degrees of dwell while cranking. This will ensure you have the proper gap and that the points are functioning okay.
What is the voltage at the coil + terminal during cranking?? When you are cranking the car with the starter, the coil gets its 12v power from a different wire than when the ignition switch is in in the "run" position. Maybe that second power source wire is bad. It comes from the starter solenoid small, side "R" terminal. The coil + terminal should have two wires attached to it: one from the ballast resistor and one from the starter solenoid.
Larry
Instructor
Joined: Aug 2012
Posts: 130
Likes: 0
From: Texas
I just finished a valve job on my 65 L79 with stock points ignition and reassembled everything and attempted to start but I have no spark. When the heads were off I installed a new Lectric Limited ignition harness, everything seemed to connect properly, it cranks over just fine, but I have no spark. I did check a couple voltages, I have 12V at the + coil terminal with the key in the run position. I also have 12V at both sides of the ballast resistor with the key in the same position. The ballast resistor was changed last year. What would be the next step to troubleshoot this problem?
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
You did mean the test light while cranking was off/on/off/on, not bright/dim/bright/dim?
You shouldn't have 12 volts on the coil side of the resistor but that won't keep you from having a spark.
Race Director
Joined: Apr 2005
Posts: 11,284
Likes: 2,146
From: Bowling Green, Kentucky
I believe you have narrowed your problem to either the coil or condenser with the check you did here. That is, unless you forgot to install the rotor?
You did mean the test light while cranking was off/on/off/on, not bright/dim/bright/dim?
You shouldn't have 12 volts on the coil side of the resistor but that won't keep you from having a spark.
You did mean the test light while cranking was off/on/off/on, not bright/dim/bright/dim?
You shouldn't have 12 volts on the coil side of the resistor but that won't keep you from having a spark.
The 12 volts he stated was with the key in the "run" position………the points were likely open when these reading(s) was taken, resulting in no current flow and 12 volts on both sides of the ballast resistor.
Agree that when the car is running, the ballast resistor will have 12 volts on one side and 8 volts (or so) on the other side. But it ain't running yet.
Larry
Thread Starter
Instructor
Joined: Nov 2004
Posts: 161
Likes: 4
From: Maryville TN
I believe you have narrowed your problem to either the coil or condenser with the check you did here. That is, unless you forgot to install the rotor?
You did mean the test light while cranking was off/on/off/on, not bright/dim/bright/dim?
You shouldn't have 12 volts on the coil side of the resistor but that won't keep you from having a spark.
You did mean the test light while cranking was off/on/off/on, not bright/dim/bright/dim?
You shouldn't have 12 volts on the coil side of the resistor but that won't keep you from having a spark.
Thanks for the help.
Melting Slicks
Joined: Apr 2006
Posts: 2,331
Likes: 61
From: Sunnyvale CA
What was the coil that failed?
Steve
Thread Starter
Instructor
Joined: Nov 2004
Posts: 161
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From: Maryville TN
Brian
Melting Slicks
Joined: Aug 2004
Posts: 3,078
Likes: 101
From: Riverhead New York
Pull the Coil Wire out of your Dist. Cap and hold it near a ground while someone cranks the engine over. Spark should be a crisp Blue color. You can also watch Points while turning engine over and see if there is a spark visible. Last resort run a wire from the Battery + to the + on your coil and see if that helps. Might just be a Coil gone bad. Al W.
Al W.