Old school ignition coil…

[SDMAN1981]

I was wondering with the old ignition coils (the outside ones) is the resistance supposed to fluctuate between hot and cold? Because when I test the resistance with a multi-meter I get higher resistance when it is hot and when I test it cold I get the factory specs (or close to) which is 10.80K ohms on Secondary and 0.700 Ohms on Primary.

I’m trying to rule out the Ignition Coil for hard starts.

So the point of the question is… Is the Primary and Secondary resistance supposed to stay the same when the coil is hot and cold?

Topic

[Lorrin Barth]

My experience with bad coils were that the engine started fine but after driving a few minutes, sufficient time for the coil to heat, it failed. For hard start I would suspect the choke, tracked distributor cap or fuel pump before the coil.

[college man]

[quote=”SDMAN1981″ post=117053]I was wondering with the old ignition coils (the outside ones) is the resistance supposed to fluctuate between hot and cold? Because when I test the resistance with a multi-meter I get higher resistance when it is hot and when I test it cold I get the factory specs (or close to) which is 10.80K ohms on Secondary and 0.700 Ohms on Primary.

I’m trying to rule out the Ignition Coil for hard starts.

So the point of the question is… Is the Primary and Secondary resistance supposed to stay the same when the coil is hot and cold?[/quote]

The resistance will change with hot to cold. Your best bet is to
get a spark tester and test spark when the problem happens. The
ohms test is inconclusive of a test.

[SDMAN1981]

[quote=”barneyb” post=117060]My experience with bad coils were that the engine started fine but after driving a few minutes, sufficient time for the coil to heat, it failed. For hard start I would suspect the choke, tracked distributor cap or fuel pump before the coil.[/quote]

What is the normal PSI for a stock fuel pump on a chevy 350?

[Lorrin Barth]

I haven’t looked it up but …………… as I remember about 5 psi. However, I don’t remember ever checking fuel pressure back when. If I thought I had a fuel pump problem I disconnect the fuel line at the carburetor and holding some container to catch the gas I had someone crank it over. The usual results were either good flow or nothing. There was one time way back in my college days when I had a bad pump and knew it but had no money. Instead, I kept driving. The car always started okay but eventually top speed dropped to about 35 mph.

[Rereonehundred]

[quote=”SDMAN1981″ post=117053]I was wondering with the old ignition coils (the outside ones) is the resistance supposed to fluctuate between hot and cold? Because when I test the resistance with a multi-meter I get higher resistance when it is hot and when I test it cold I get the factory specs (or close to) which is 10.80K ohms on Secondary and 0.700 Ohms on Primary.

I’m trying to rule out the Ignition Coil for hard starts.

So the point of the question is… Is the Primary and Secondary resistance supposed to stay the same when the coil is hot and cold?[/quote]

Coil resistance measurements change rather a lot with temperature. Not a factor of two, could could be 30% or so, if really hot. The hotter it is, the higher the resistance.

The spec is probably for something near room temperature.

[Author]

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