differences in coils exposing a weakness?

[twobone]

After sitting for a while my car would not start. I determined I was not getting a spark.

 

I have a new Bosch blue coil which has a built in capacitor.

 

When I temporarily swapped in a hotter coil without a capacitor I got a spark.

 

So I think the final culprit is my old battery. While it is putting out 12 volts, I think she is low in amps. I suspect she is not putting enough juice out to make a good spark with the resistor'd coil.

 

Make sense?

[pi7ot]

An old battery is a potential weak link in the ignition chain, until it is tested.

The coil involved in the no-spark event is equally suspect.

Coils are usually long lived parts. I have only ever replaced one Bosch.

It's all guesswork until the battery is load tested and the primary and secondary resistance specs of the coil are measured.

 

m

[twobone]

The battery is an old wet cell that came with the car from japan. The water level is fine, but she seems to be fairly weak.

 

I think a switch to a modern sealed battery is in order.

[danilo]

Hopefully you've sorted it?

Don't discount the possibility of a bad coil, especially the Bosch 'blue' type.

I've had 2 of the excreable things die within a few months of install... right out of their Bosch boxes.. which said 'Made in Brazil (in a corner :-). Distributor of the things suggested reverting to the OEM coil,

which I did and subsequently never looked back.

OEM Bosch seems to be of a much higher standard.

[jimrankin]

If you have a stick test this way. Try to start with the starter, if no spark do a roll/push start and if it fires the coil is good, the battery is too weak to support the current draw of the starter without dropping the voltage too low for the coil to spark. This still does not mean that the coil is up to specifications, it could be getting weak and needs a fully charged battery to work.

You can also test the coil by using a spare spark plug, widen the plug gap to about twice normal, bring the motor up to that plug firing position in the distributor, connect the HT lead to the spare plug (ground the plug)disconnect the coil wire and then touch power to the primary side of the coil with a jumper from the battery. If it's working well even a weak battery will fire it since it's seeing no other load, not even a turned on ignition system.

If you have an old spark plug HT lead you can just use it right off the coil as an even simpler way to do this test.

[jlumba81]

Any autoparts store should be able to test the battery for you.