How do you test an ignition coil to see if it is bad?

Thanks in advance.

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I have never met a man so ignorant that I couldn't learn something from him. -Galileo Galilei, physicist and astronomer (1564-1642)

Pull the codes and they will tell you which of the three coil packs are bad. Generally the car will run quite roughly.

If one does not know how to pull codes (and I have over 500,000 miles on my Benzes) and I do not have a code reader...is there a way to tell if a coil is bad?

thanks.

__________________
I have never met a man so ignorant that I couldn't learn something from him. -Galileo Galilei, physicist and astronomer (1564-1642)

I'd recommend building yourself a code reader from Radio Shack parts and doing it that way. Otherwise it's just trial & error / throwing parts at it. You can also always take it to a shop for diagnosis/repair.

Here are instructions for building an inexpensive code reader, and the document that helps you decipher the codes for your car is here.

Here's the procedure for obtaining and then clearing codes.

Cheers,
Gerry

A faulty coil may or may not result in a code on the M104. From my experience, a defective coil that causes rough running at idle, and/or miss under acceleration will not result in a stored code.......

J. M. van Swaay

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1994 E320 Wagon, 230,000 miles
1995 E320 Sedan, 106,000 miles
1994 E500 Sedan, 79,000 miles

My wife's 1995 wagon did store a code, which pinpointed the coil pack for me to replace. Worked a charm. Maybe that was an anomaly though -- but there are separate codes for each coil pack.

Cheers,
Gerry

Don't forget there are three parts to the coil pack.

coil
plug boot under the coil
wire to second plug

Damage to the second or third will also give the bad coil symptom.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles