A six cylinder in-line engine has a power impulse every 720 degrees/6 i.e. 120 degrees of crankshaft rotation. The crankshaft has six crank-throws placed at 120 degrees out of phase with one another, which can be arranged only in three planes. Therefore, the crankpin phasing is arranged in pairs. For heavy-duty diesel engines, seven journals and bearings are provided, at each end and between adjacent crankpins. For petrol engines only 4 or 5 main journals are provided. The firing order with the crankshaft arrangement shown in the attached figure is considered. With piston 1 at the top of the compression stroke, its opposite piston 6 is at the top of its exhaust stroke. Rotation of crankshaft through 120 degrees brings pistons 2 and 5 to their TDC and either one of these can be arrangement to complete a compression stroke. If piston 5 is arranged to be at the end of compression and at the start of its power stroke, then piston 2 must be on its exhaust stroke. Rotation of crankshaft through second 120 degrees positions pistons 3 and 4 at the TDC, so either one of these can be on the compression stroke. If piston 3 is made to be on compression, piston 4 must be on its exhaust stroke. A third rotation of 120 degrees brings pistons 1 and 6 back again to TDC, where piston 6 is arranged to be on the compression and piston 1, therefore, be on its exhaust stroke. A fourth 120 degrees rotation brings pistons 2 and 5 to their TDC. Piston 2 is now on its compression and piston 5 on its exhaust stroke. Rotation of crankshaft through fifth 120 degrees brings piston 3 and 4 to TDC. Piston 4 is on compression and piston 3 on its exhaust stroke. Final rotation of 120 degrees completes the 720 degrees displacement of crankshaft and brings the pistons into positions for the next cycle. This cycle provides a firing order of 1, 5, 3, 6, 2, 4. If the phasing of paired crank-throws 3 and 4 and 2 and 5 are interchanged, then a second equally suitable firing-order of 1, 4, 2, 6, 3, 5 is achieved. This arrangement provides excellent dynamic balance and evenness of torque, and is preferred for engines larger than 2.5 liters provided length is not a prime consideration.
Fig. Fig. 1: 2.0L (VIN M) Engine Firing Order: 1-3-4-2 Distributor Rotation: counterclockwise
Fig. Fig. 2: 2.3L (VIN A, D, and 3) and 2.4L (VIN T) Engines Firing Order: 1-3-4-2 Distributorless Ignition System
Firing Order: 1-3-4-2 -nl-> Distributor rotation: clockwise" rel="width:950,height:660" index="2" $included="null">
Fig. Fig. 3: 1985-86 2.5L (VIN U) Engine -nl-> Firing Order: 1-3-4-2 -nl-> Distributor rotation: clockwise
Fig. Fig. 4: 1987-91 2.5L (VIN U) Engine Firing Order: 1-3-4-2 Distributorless Ignition System
Fig. Fig. 5: 3.0L (VIN L) Engine Firing Order: 1-6-5-4-3-2 Distributorless Ignition System
Fig. Fig. 6: 3.1L (VIN M) Engine Firing Order: 1-2-3-4-5-6 Distributorless Ignition System
Fig. Fig. 7: 3.3L (VIN N) Engine Firing Order: 1-6-5-4-3-2 Distributorless Ignition System
Fig. 3.0L Engine Firing order: 1-2-3-4-5-6 Distributorless ignition system
Fig. 3.5L Engine Firing order: 1-2-3-4-5-6 Distributorless ignition system
Fig. 3.0L Engines without DIS Firing order: 1-2-3-4-5-6 Distributor rotation: Counterclockwise
Fig. 3.0L Engines with DIS Firing order: 1-2-3-4-5-6 Distributorless ignition system
Fig. 3.5L Engine Firing order: 1-2-3-4-5-6 Distributorless ignition system
Fig. 3.0L Engine Firing order: 1-2-3-4-5-6 Distributorless ignition system
Fig. 3.5L and 3.8L Engines Firing order: 1-2-3-4-5-6 Distributorless ignition system
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3.8L engine Firing order: 1-2-3-4-5-6 Distributorless Ignition System
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