5.3L V-12 Firing Order
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Saliah,
If you haven't done so already now would be the time to remove the distributor cap and take a peek at the rotor....as they often burn through. With the cap off you'll also see that the Marelli rotor and distributor cap are a dual plane design which explains why the actual firing order of the cylinders is the same as a Lucas ignition car but the placement of the wires on the distributor cap is different.
Cheers
DD
If you haven't done so already now would be the time to remove the distributor cap and take a peek at the rotor....as they often burn through. With the cap off you'll also see that the Marelli rotor and distributor cap are a dual plane design which explains why the actual firing order of the cylinders is the same as a Lucas ignition car but the placement of the wires on the distributor cap is different.
Cheers
DD
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I have a 94' XJ12 V12 Marelli - except the "B1" cylinder is clearly forward of the passenger side bank..... yet isn't ALL engines most forward cylinder no.1 ?
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is the Distro position correct on this gif? ie: are the firing order on cap, actual position on vehicle?
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The XK engine is numbered from back to front.
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The firing order is 1A,6B,5A,2B,3A,4B,6A,1B,2A,5B,4A,3B
But since the Marelli system has a two plane rotor, the numbers on the cap are 1A,1B,5A,5B,3A,3B,6A,6B,2A,2B,4A,4B
#1 cylinder on a Jag V12 is "1A", which is front most cylinder, RH side
Weird, I know
Cheers
DD
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Yes, but the V12 is not an "XK" engine :-)
Cheers
DD
Cheers
DD
Last edited by Doug; Jul 14, 2022 at 10:15 PM.
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Cheers
DD
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Genuine question Doug. Why is it "weird", what am l missing?
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The norm is that the layout of the wires on the cap matches actual firing order of the cylinders, as seen in the illustration of the Lucas system.
On Marelli system, with the dual plane, dual tipped rotor, the layout of wires on the cap does not match the firing order of the cylinders. Which is weird
The "A bank" - "B bank" numbering system is also a little weird. I'm not aware of any other V-type engine using this system....but I could be under-informed on that!
And, typically, the #1 cylinder (for the purposes of engine timing, finding TDC, and such) is the front-most cylinder of the front most cylinder head (the head that is further forward on the engine block). The uninitiated, working on a Jag V12, would go to 1B when in fact they should be going to 1A.
Cheers
DD
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From: Australia
The norm is that the layout of the wires on the cap matches actual firing order of the cylinders, as seen in the illustration of the Lucas system.
On Marelli system, with the dual plane, dual tipped rotor, the layout of wires on the cap does not match the firing order of the cylinders. Which is weird
The "A bank" - "B bank" numbering system is also a little weird. I'm not aware of any other V-type engine using this system....but I could be under-informed on that!
And, typically, the #1 cylinder (for the purposes of engine timing, finding TDC, and such) is the front-most cylinder of the front most cylinder head (the head that is further forward on the engine block). The uninitiated, working on a Jag V12, would go to 1B when in fact they should be going to 1A.
Cheers
DD
On Marelli system, with the dual plane, dual tipped rotor, the layout of wires on the cap does not match the firing order of the cylinders. Which is weird
The "A bank" - "B bank" numbering system is also a little weird. I'm not aware of any other V-type engine using this system....but I could be under-informed on that!
And, typically, the #1 cylinder (for the purposes of engine timing, finding TDC, and such) is the front-most cylinder of the front most cylinder head (the head that is further forward on the engine block). The uninitiated, working on a Jag V12, would go to 1B when in fact they should be going to 1A.
Cheers
DD
I think you would agree however that to the initiated (as opposed to the UNinitiated) all things Jaguar make perfect sense.
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Naturally
Cheers
DD
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