What causes a coil to go bad? I started it up this AM and then I took it for a SHORT 4 mile ride, stopped back at my house, shut off the car, for a minute. Came back out of the house and it would not start. CRANK AND CRANK, But no start. After a bit, with the gas pedal floored (as if flooded) it finally tried to start and did start.
I "THINK" that the problem was in the coil. When the
car was warmed up, and didn't even try to start. I checked for spark, and it seemed weak OR sporadic at times.
So, I pulled aCOLD (working)coil from another car, and then as soon as I hit the starter on my RR it started right up. I "think" that if I let the coil cool down, (or let the whole car cool down, then, it would start again. (happened before) What would cause this? The car ran GREAT while it was running and didn't show any signs of misfires or anything like that? HOW do you BENCH TEST a coil? I would like to eliminate it as aproblem... if you know what I mean.
Please don't say, Just buy electronic ignition as I want to keep the dual points and original parts in my car to keep it looking original.
Thanks!
Jim
Coil problems/no starting when Hot
-
Seabee
- Founding Member
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Inside the case of your coil is a core wrapped with wire (coils of wire, hence the name). It is a transformer essentially. Like the transformer hanging on the power pole steps the voltage down for your house, your ignition coil steps it up.
Here's the rub - for it to work nicely, those wires need to be small (lots of wraps), and insulated. One of the by products of transformer operation is heat. One of the enemies of small insulated wire is... heat.
Over time heat degrades the insulation on the wires, as well as chafing action from the strands expanding and contracting from hot/cold cycles. Once the insulation is broken down shorts begin forming between adjacent strands of the windings. When this happens the degradation accellerates; the shorts lower the effeciency of the transformer and create more heat.
Many times - especially in auto coils this happens. When it is cold it has "shrunk" enough to function. As it heats up and expands, more wires short together and it ceases to deliver good voltage.
Coil manufacturers usually publish the range of Ohms resistance that the coil should show on the primary and secondary sides. This is the most common test. More thorough testing with "meggers" to test for shorting or other ugliness in the coils windings can be done, but usually if it is out of spec on the ohm test for the windings, or suspect to be bad, it is chucked for a new one.
If I read your post right you've already identified the coil as the culprit right? When you put a different coil on it fired up.
No need to go electronic if you don't want to 'cause you'd still need a coil! Just get a good one. I think MP makes their Blaster or similar in a plain black case that looks bone stock.
Here's the rub - for it to work nicely, those wires need to be small (lots of wraps), and insulated. One of the by products of transformer operation is heat. One of the enemies of small insulated wire is... heat.
Over time heat degrades the insulation on the wires, as well as chafing action from the strands expanding and contracting from hot/cold cycles. Once the insulation is broken down shorts begin forming between adjacent strands of the windings. When this happens the degradation accellerates; the shorts lower the effeciency of the transformer and create more heat.
Many times - especially in auto coils this happens. When it is cold it has "shrunk" enough to function. As it heats up and expands, more wires short together and it ceases to deliver good voltage.
Coil manufacturers usually publish the range of Ohms resistance that the coil should show on the primary and secondary sides. This is the most common test. More thorough testing with "meggers" to test for shorting or other ugliness in the coils windings can be done, but usually if it is out of spec on the ohm test for the windings, or suspect to be bad, it is chucked for a new one.
If I read your post right you've already identified the coil as the culprit right? When you put a different coil on it fired up.
No need to go electronic if you don't want to 'cause you'd still need a coil! Just get a good one. I think MP makes their Blaster or similar in a plain black case that looks bone stock.
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Jims68
- Sweptline.ORG Pioneer
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Thanks guys for the input!!
Seebee,
thanks for that great explanation on how coils work and can break down. I (and my wife) understood it completely. It does explain why my car wouldn't start after it was hot... Yes, the "other" coil is working and starts the car after it has gotten warmed up to operating temps.
Russ,
yes, I had replaced the condenser first and also reset the dual points before I had swapped out the coils. No... it acted as if it was flooded, but it really wasn't. I think what had happened was the car had actually had time to cool down a bit in that period. When I had replaced the coil the car was hot, and I didn't even touch the gas pedal and the car popped right off and started.
I ordered new tires for it yesterday, and they should be in today. I am staying with the original 14X6 magnum 500 rims and I am getting 225 R70 14" Goodrich TA Radial tires. Should have a big improvement from the Goodrich Bias 205 70 14" tires I have on it now.
Jim
Seebee,
thanks for that great explanation on how coils work and can break down. I (and my wife) understood it completely. It does explain why my car wouldn't start after it was hot... Yes, the "other" coil is working and starts the car after it has gotten warmed up to operating temps.
Russ,
yes, I had replaced the condenser first and also reset the dual points before I had swapped out the coils. No... it acted as if it was flooded, but it really wasn't. I think what had happened was the car had actually had time to cool down a bit in that period. When I had replaced the coil the car was hot, and I didn't even touch the gas pedal and the car popped right off and started.
I ordered new tires for it yesterday, and they should be in today. I am staying with the original 14X6 magnum 500 rims and I am getting 225 R70 14" Goodrich TA Radial tires. Should have a big improvement from the Goodrich Bias 205 70 14" tires I have on it now.
Jim