Posted by oscar on Monday, January 14, 2002 at 7:46PM :
In Reply to: Mystery starting problem. posted by Pat Holscher on Monday, January 14, 2002 at 11:42AM :
Pat,
You likely have a ground problem between the engine & frame and the cab or some corrosion in the wiring harness (check the firewall plug). The ignition system depends on the voltage betweem the positive side of the coil and the ground side of the spark plags. When the cab ground strap be comes corroded the cab where the coil is grounded begins to electrically "float" above the engine ground. Since the total voltage in the system remains at the battery voltage the voltage across the coil decreases as the voltage drop across the ground strap increases. Once you have a 2 to 3 voltage "float" the spark plugs will not spark any more as the voltage across the coil has dropped to 10 or 9 or lower as the voltage drops as the engine is cranked.
My w200 has a grounding wire behind the grill that shorts out the rear lights if my trailer is connected.
Good luck
oscar
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