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What is the proper order to re-connect the spark plug leads on a 1995 VS commodore?

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February 25, 2008 3:54PM

If the coil packs (the v6 engines went to 3 separate ones about half way through the VN model) are original or the correct genuine replacement(s), the cylinder numbers will be on top of the individual coils. They fired in pairs, like some motorcycles, and mixing them up will cause very bad misfiring. This is because the "return" lead (which was the one of the pair that went to the non firing plug, for that spark instance) was selected to have its cylinder at (or near) Top Dead Centre on the EXHAUST stroke, giving an easy passage for the spark, as it not only had to fire the intended cylinder, which was near maximum compression pressure with the fuel/air mixture, but had to travel the "return" route through the block and heads (easy) but also had to jump the gap in the opposite spark plug (not so easy, but easier in the lower pressure with the exhaust valve open) and then back up the opposite lead to the coil to complete the circuit. This meant one misfiring plug (or bad lead) would often cause two cylinders to misfire. Pedants please don't attack me about direction of electrical flow and what-not, this explanation makes it simple enough that you don't need three years study to understand the basic works.

Cylinder numbering was easy (GM liked it simple). Number one was the most forward (or closest to the water pump). Two was the next most forward (which meant the opposite side of the engine [as the cylinders were staggered], at least in Holdens with rear wheel drive). Three was immediately behind one, with five behind it. Four and six obviously and in that order behind two.