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  #1  
Old 09-05-2003, 05:52 PM
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Ignition Coils: Weird variance of opinion among techs

Guys (and, excuse me, Gals):

I've got the M117 engine, so I have the old standby coil - the Bosch old-fashioned model with the wire and boot on top. The tubular one. I think mine must be well over 20 years old. anyway.....


Since I was getting loss of power and fluttering under load conditions and heat, and have almost eliminated fuel problems, I removed it and took it this morning to my old tech over near where I used to work. Now this guy's been around and crawled under old Benzes from before I was born. He says - "Don't even bother testing it. I don't care. I've seen a million of these, and they never, ever fail". (I'm in South Florida). He said, again without even looking, "It's got to be the ECU in the box by the driver-side fender. That's always the culprit).

So I haven't pursued it.

But now I'm thinking......that'snot what you guys have been saying here. You guys.....do these old-style coils fail over time and load conditions, also heat mixed in? Or is my 'tech' absolutely right. What'dya think?

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Old 09-05-2003, 06:00 PM
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One more thing.......

One more thing....

Tomorrow morning, or tonight (if store's still open), I want to get the best type of electrical meter which can check my circuits and particularly, coil output and spark at plug boots. Questions:

If I go to Discount Auto parts:

1. What device is best, and about how much should I pay for one.

2. I have M-117 motor. What should I be looking for, in terms of coil output/input, and spark at wire boots? How do I test spark at wire boots, which is the ultimate issue, under load conditions?

thanks for specifics. This will be better than guessing and just replacing parts.
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Old 09-06-2003, 08:42 AM
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And.....

If I get the meter, besides outlining testing procedure for me,
what specs should I be watching for on coil and sprak plug leads?


M117 engine (Euro).

PLEASE!!!!!!Want to dothis over weekend.

Bob
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  #4  
Old 09-06-2003, 08:59 AM
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Last I looked replacement bosch coil was around $50..... so the testing apparatus may cost more than the cure.

I've replaced a couple of coils over the years, owning mostly 6 cyl MB's. The spark should be blue and strong - not orange or yellow.
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Old 09-06-2003, 09:21 AM
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Diesel:

I',m opting for the coil. Wouldn't hurt to have a new one, anyway.

Where can I get one today? IE, what major chain (pep boys, etc) might best have one of these bodch units (they were so common), so I don't have to wait for one?
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  #6  
Old 09-07-2003, 08:39 AM
Manya
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whole crap! $50US for a simple tubular coil. They only cost around $45AUD here.
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Old 09-07-2003, 09:06 AM
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$50 might be about right these days, if you want a genuine Bosch coil. You might be able to find a cheaper Standard or Echlin replacement.
If you have the specs, you can do some coil tests with a volt-ohmmeter.

Happy Motoring, Mark
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Old 09-08-2003, 02:24 AM
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When you remove the old coil you'll find a ground wire from the distributor which attaches to one of the bracket bolts. Make sure it is tight. I had to add a washer in there because no matter how hard I tightened the bolt it flopped around causing all kinds of ignition problems.
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Old 09-10-2003, 08:32 AM
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Dieselhard: I am interested n your coil

Dieselhard:

I am interested in your coil, thank you. Yes, mine is the blue one. Are you sure it is the same in output and capacity? How do we know?

Otherwise, I'll take it.

Contact me at: bobboyer5@aol.com, and we can work out shipm,ent/p[ayment details. $15.00 for the right new one can't be beat.

Bob
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  #10  
Old 09-11-2003, 01:23 AM
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Ignition Coils: Weird variance of opinion among techs

Damn you folks got me thinking. In 13 years of pro wrench bending I can't remember ever changing a coil unless it was cracked on top or leaked oil. This includes two years with VW/Porsche (Bosch) that I had no failures.
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Old 09-11-2003, 08:18 AM
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To: Hill

Yeah, but....

Does it matter if the coil is well over 20-plus years old?
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  #12  
Old 09-12-2003, 01:20 AM
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you know, you can test these coils with a vom. will tell you a lot.

check them for continuity. check them for resistance[somewhere you can find the spec].

also, inspect the high tension tower for corrosion. if it has any, clean it up. if you can't find a coil tower clean-out brush at your auto parts store, check out stitt-sparkplug.com. they offer them.

become practical.
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Old 09-12-2003, 02:28 AM
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"Does it matter if the coil is well over 20-plus years old?"

You would think it would but we worked on a lot of old porsches. I also don't remember any of the 50's to early 70's Alfas eating coils. My old Dodge, 350sl, and landcruiser have had the same coils for over 30 years. Now when cars went to HEI and CD syle ignitions then there were some problems.

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