Testing a coil with a timing light?
Thread Starter
Racer
Joined: Oct 2010
Posts: 259
Likes: 3
From: Plano TX
Testing a coil with a timing light?
So.....I was going up through the gears today at about half throttle, and at about 3500 rpm in second gear the motor died and I came to an inglorious halt.
Wouldn't restart and couldn't even detect it firing.
Got it towed home and eventually, I thought about hooking up my timing light and see if it would fire when trying to start. Seemed to me that if there was enough juice there to start the dang thing it should light a timing light. Had plenty of juice in the battery but when turning over the motor got no flash from the light. Hooked it up to the coil to distributor wire and got no flash there either.
Electricity has always been a mystery to me, for the most part, but with plenty of battery shouldn't the timing light fire when attempting to start the motor?
Hoping maybe the coil or something else simple went south on me.
Wouldn't restart and couldn't even detect it firing.
Got it towed home and eventually, I thought about hooking up my timing light and see if it would fire when trying to start. Seemed to me that if there was enough juice there to start the dang thing it should light a timing light. Had plenty of juice in the battery but when turning over the motor got no flash from the light. Hooked it up to the coil to distributor wire and got no flash there either.
Electricity has always been a mystery to me, for the most part, but with plenty of battery shouldn't the timing light fire when attempting to start the motor?
Hoping maybe the coil or something else simple went south on me.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
yes your timimg light should flash when hooked up to the high tension lead.....
what year vette is this? if this is an external coil look and see if the two wires on it on either side of the coil are hooked up. the + side is power coming in and the - side goes to the distributor.
what year vette is this? if this is an external coil look and see if the two wires on it on either side of the coil are hooked up. the + side is power coming in and the - side goes to the distributor.
Last edited by bobs77vet; Apr 7, 2012 at 09:09 PM.
Thread Starter
Racer
Joined: Oct 2010
Posts: 259
Likes: 3
From: Plano TX
yes your timimg light should flash when hooked up to the high tension lead.....
what year vette is this? if this is an external coil look and see if the two wires on it on either side of the coil are hooked up. the + side is power coming in and the - side goes to the distributor.
what year vette is this? if this is an external coil look and see if the two wires on it on either side of the coil are hooked up. the + side is power coming in and the - side goes to the distributor.
I wasn't aware that a coil could fail so catastrophically, but maybe so. I had a flash of horror that I lost a timing chain or sprocket, but that just doesn't seem reasonable, not at 3,500 rpm.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Points closed up, condenser shorted internally, breaker plate ground broke. Other things to look at too before you condemn the coil. Check the coil for continuity with a meter.
Melting Slicks
Joined: May 2009
Posts: 3,079
Likes: 314
2024 C3 of the Year Finalist - Unmodified
I had a coil fail on my '73 Harley at full throttle. When it decided to fire again, it blew the rear cylinder off the bike. After rebuilding the engine, it still ran like crap. Replaced the coil with a known good and it purred like a kitten. Coils can and do go bad, in many different ways. Keep a spare on hand or use a friend's to troubleshoot. Only takes a minute to find out.
