III series xj6 after replace intake valve rubbers

I have a problem to ask you: I replaced the intake valve rubbers with original jaguar special tools and some self-made without dismantling the cylinder head; reassembled with correct distribution the car non start but with battery runs well.
cylinder 1 be the one closest to the passenger and 6 the one behind the radiator and the ignition sequence is the prescribed one; the car alone as a few flashback and bursts without good start.
grazie carlo

To clarify: the ignition sequence is correct.
The camshaft is set correctly (both notches and the timing pointer at the crankshaft).
It cranks well and has compression.
It tries to start sometimes but only backfires or dies immediately?

Compression in alls cylinder is good; not start: only baang something, I think that i go on the rotor sequence not in counterclockwise: camshaft with the jaguar tools are ok and the timing pointer crank. is with compression on 6 cylinder.
tomorrow I go with 1-5-3-6-2-4 in counterclockwise on the rotor of spint.
many t.

It is incredibly easy to misplace plug leads, getting the sequence wrong, Briciola…

The critical first step is set the engine to TDC on the damper timing scale. The dist rotor will now point either to the #1 or #6 cylinder - but(!) only one of them is on the compression stroke, ready to fire. This cylinder is then the reference point for the sequence…

If #1 is ready to fire the sequence is indeed 1-5-3-6-2-4 counterclockwise on the dist lid. If it is #6; the sequence on the lid is 6-2-4-1-5-3. The tricky bit is to find which of the two cylinders is ready to fire…

One way is to remove oil filler cap and look at the exhaust cam lobe; if it points away from the valve, the valve is closed - signifying #6 is on the firing stroke. If not; #1 is…

The other way is to remove #6 spark plug and turn the engine towards TDC with a finger on the plug hole. If compression is felt; the piston is coming up on the compression stroke - #6 is then the reference cylinder and the rotor should point to #6 plug lead. Or rather, the #6 lead should be placed there to start the sequence…

Now, when you place the plug wires; trace the lead from the reference plug to the dist lid hole the rotor is pointing to - and trace back to verify. Then trace lead from the next plug in the sequence to the next hole counterclockwise. And the next and the next in sequence…:slight_smile:

I’m dotting the 'i’s and crossing the 't’s - any shortcuts and things may go awry. I have misplaced more leads than I care to remember - trying to be smart…:slight_smile:

As an aside; you should have verified the sequence while you were replacing the intake valve rubbers - reading the cam lobes positions at TDC…

xj6 85 Sov Europe (UK/NZ)

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Please define Baang something… is that an ignition Baang like engine not firing correctly, or like a thump baang something hitting internally to the engine?

Ignition bangs aren’t plesant and as Frank stated can be easy to get the distributor wiring off (I can’t count how many times I’ve done that). to put into perspective I just rewired a distributor cap, and I was amazed I got it right the first time. Enough said on this topic.

After fitting new valve seals (rubbers), bolted up the cam shafts onto the cam gears, did you rotate the engine by hand check the cam timing with the cam positioning tool on both cams to make sure the cam was still in proper position. then do that process again?
Also did you check to ensure there wasn’t any slack in the cam chain?

no backfires only no internal engine noises cam in position and chain ok.
I think Frank is right that I thank, I’ll let you know.
thank you

A possible preliminary inspection, Briciola - assuming that sequence is the cause of the problem…

Set the engine to TDC and check rotor position. If the rotor points to #1 (or #6) - assume that that is ready to fire. The check plug leads as described in ign sequence. This will verify if leads has been crossed if so; rectify and try starting…

If sequence is correct; assume that you have used the wrong reference cylinder. Change over the #1 (or #6) lead - and reset sequence as previously described…

After all that work; if engine doesn’t change its behaviour - it is not the sequence that causes the problem. Back to the drawing board…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

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all ok ; the car runs very good

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Good for you to have the car running well. In fairness to those that posted helpful hints to you, could you please let us know what the problem was and how you fixed it? That would be very helpful to everyone.
Thank you and glad you’re up and running.

Thank you for providing the update. Nicely done!

Cured by pure magic… ?

only the ignition sequence to cylinder wrong; it was necessary to check if 1 or 6 were in compression
grazie a tutti

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You are not the first, Briciola…

The best preparation is to ascertain where the rotor points before disconnecting plug leads…:slight_smile:

xj6 85 Sov Europe (UK/NZ)