Expert: Josh Fields - 3/15/2006

Question
Josh,
my on just bought an '87 325is & he attempted to change plugs & wires & is having trouble - do you have a diagram with the firing order for wires on cap & also where additional wires go with the new set he purchased
thanks
John

Answer
John,
 Most wire sets are already numbered, so you can look on each wire and tell where it is supposed to go.  However you need to know where to plug the ends into the distributor cap.  I know some caps are numbered, although the text is REALLY small and you would have to look really close to see it.  The firing order is 1-5-3-6-2-4 , and should run from the top down (#1 being the very top connection.  Notice there is one connector on the distributor cap that is "Off-line" with the rest. It is usually in the middle of all of the other connections.  This one is for the coil-wire.  I would connect the coil-wire first, then start plugging in my plug wires.  since the firing order starts with 1, put #1 plug's wire there.  Then the second number is 5, so to go the next connector DOWN and put #5's plugwire in the connector.  Make sure the wires are connected well, they should "click" when they are on good.  
 To be honest, I would change the distributor cap and rotor while I was replaceing the plug wires. (unless you already have).  At least pull the distributor cap off and inspect it, the points get corroded and make a weak spark (if any) to the spark plugs.  If they are really eroded, it needs to be replaced, but if there are just a few black spots on the pins you can take sand paper and clean off any carbon, but dont take off too much metal!

 Hope this helps
 Josh