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1990 420 SEL 210,000 mi. ,1989 560SL 101,000 mi.
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17 Posts
Discussion Starter #1
Replaced the coil on my '91 420 SEL thining it was the problem with getting no spark to the plugs. This didn't make any difference. The car was running poorly when I parked it and when I got in to drive it again it would not start. I checked for fuel flow and there is plenty of gas when the pumps run so I pulled a plug and cranked then engine but got no spark at the plug. My mechanic said it was probably the ignition coil.

What should I look for now?

Thanks in advance.

Steve
 

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1,648 Posts
A new "mechanic" and a multi-meter See what the voltage across the coil is doing when you crank. Also see if the ignition controller is getting its input signal.
 

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560SEC, 190E, Frontier, 240Z
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1,329 Posts
Where'd you get the coil? Brand new?
There is a spec to check resistance on the coils. I forget the exact spec... but a "ONE" or "ZERO" is a bad.

Coil lead wire ok?

Isn't there some way to check the Crank Position Sensor?
 

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1990 420 SEL 210,000 mi. ,1989 560SL 101,000 mi.
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17 Posts
Discussion Starter #4
Thanks for the replies. Yes, it is a new Bosch coil. I will check the coil lead and resistance with a multimeter and report back. I have not researched how to check if the ignition controller is getting an input signal but will look for that information.

Thanks
 

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Depends on the day!
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13,337 Posts
I'd say EZL or ignition switch would be the more likely culprit.

Jonathan
 

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1990 420 SEL 210,000 mi. ,1989 560SL 101,000 mi.
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17 Posts
Discussion Starter #6
I finally had the car towed in to the local independent Mercedes mechanic and after testing everything including the new coil he determined it is the ignition control module causing the problem. The qoute to replace it with labor and diagnosis was $2,700!

Any suggestions on where to find a used one or is there some other work around?

Will a module for any V-8 work or is it very specific to model and year?

Thanks,

Steve
 

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Registered
1990 420 SEL 210,000 mi. ,1989 560SL 101,000 mi.
Joined
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17 Posts
Discussion Starter #8
Just wanted to follow up on this and post a conclusion. I found a used ignition control module on Ebay for $275 and had it installed. That did the trick, the car seems to run great now.

Thanks for all the help on this. Jonathan was right!
 
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