Question about Mercedes-Benz 300-Class
If there is no spark, either no electrical at the primary coil or the coil is not working.
if you already measure primary/ secondary resistance to confirm it is OK. Here is to test it - making electric pulsed signal at the primary terminals to see it spark at the secondary terminal.
You want to confirm everything works from the coil, so you can find out what causing the coil is not working. Here are what to check the coil before a replacement::
1- Disconnect the Positive cable on the battery.
2- Hook a spark plug directly to the coil wire ( the one coming to the center of distribution cap)
3- Find a long double wire so you can connect from the terminals of the primary coil to the battery.
4- Connect each wire end to the terminal of the primary coil. It doesn't matter which polarity.
5- Connect 1 wire to the chasis ground.
6- Hold the other wire and quickly swipe it over the positive terminal of the battery. Reapeat it until are sure that you get spark or not.
7- You should see or hear a spark. If this is the case your coil is good. If itis not, your coil is bad and it need a replacement. Problem is solved.
4- If the coil is good, the problem would be from the Primary of the coil back to the ignition key: No electrical signal to turn on the coil.
Posted on Jul 25, 2009
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Posted on Jan 02, 2017
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