Coil question

[Scutch]

It may be coincidence but on had a coil go bad on me two months ago and now I have a second one the seems to be going bad. I took it somewhere and they hooked it up to a box and when the car missed the little graph that shows the coil current jumped. When the graph showed all the cylinders the missing seemed to occur randomly on different cylinders.

It is exhibiting the same symptoms as the last one that when bad. When I am at a stoplight with my foot on the break it misses intermittantly (it's an automatic). As the car gets hot the missing increases. When it is cool it is not so bad, but still misses every minute or so. Eventually it got worse and the coil failed altogether.

Both of these coils were used and I don't know how old they were, but as I buy a 3rd coil my question is, is there anything that could be burning out the coil prematurely?

Could it be the resistor or the thing that looks like a condensor that has a wire to the positive side?

BTW all the other ignition parts are new, and the distributor just got rebuilt.

Thanks for any help.

Eddie

[Blue 72 250]

Originally Posted by Scutch

is there anything that could be burning out the coil prematurely?

Could it be the resistor or the thing that looks like a condensor that has a wire to the positive side?

BTW all the other ignition parts are new, and the distributor just got rebuilt.

Thanks for any help.

Eddie

Yes, and Yes. If you don't have the correct resistance amount the coil will overheat and fail. Check to see if the coil gets hot to the touch when running the car. If so, then you need more ohms of resistance. There is a wealth of information concerning this problem on the forum.

Finally, if it was me I would buy a new coil and avoid used ones (but that is just me).

[Scutch]

I checked out a lot of the info on coils and the ohm resistance, but am unclear which it closest to "stock" for my car.

Online, it seems the Bosch red coil is what is recommended now, but do I need to change the resistor to match that one? If so what should the resistance be?

My book mentions nothing about coils or its specs, and the past posts talk mostly about the pertronix kits.

Also, one post mentions that plugs with too wide a gap may stress the coil. Could that be an issue? My plugs are gapped at .035.

[todds]

There's an OEM coil on ebay for your car here:

http://cgi.ebay.com/ebaymotors/BOSCH-COIL-Mercedes-Benz-190-200-220-230-250-280-300_W0QQitemZ130065603760QQihZ003QQcategoryZ10076QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

No idea about the seller though, he's in Cypress?!?? It's kind of a gamble, but I bought one from him, I'll let you know how it goes.

Nothing like original parts to make it run right...

[230/8]

Scutch:

Check this site and call Phil for parts...there is a original style red coil listed. Look carefully at the enlarged photo for it and you can make out the warning to use resistance of 1.8 ohms. That would equate to using a 1.8 ohm resistor, Bosch # 0.227.901.014, this resistor is also avaialble. You have to look for the resistor, or simply call Phil for the right stuff.

FYI, my '69 uses only one 0.9 ohm resistor with its stock coil. While the wrong resistance might stress a coil, the usual result is greatly reduced point life (burned up because of too low resistance = too high current flow) or too low spark energy because the current flow through the coil is too low (too high a resistance).

230/8

[Scutch]

Thanks much for the reply. Do you know if the resistor that comes stock is the 1.8 one? Do you know if they wear out?

Also, what was the site you were talking about?

Eddie