Question about 2006 Jaguar XK-Series
Hi I have a problem with the engine popping back through the three new weber carbs my father in law put on before he passed away.Iknow he had the head off a few years back so i dont know if he ever got it to run correct.I did a compression check becouse i know it sat for sometime when he got sick.I have 80 to 90 psi in 5 cyls and 30 psi in 1cyl after i ran it.So i thought i would ck the cam timing but cant find any marks to line up.I have been a nissan tech for 30 + years but not much to do with weber carbs.I have yet to find a manuel but the plugs wires and points are ok.Any help would surly be appreciated.Thank you Dale
The carbs are likely not the problem. It is the low cylinder. I agree with guru that the valve clearance is the culprit. More than likely you have an intake valve that is not closing all the way, creating a backfire through the carbs. Don't run the engine any more un til it is fixed, as you will burn that valve and the head will definitely have to come off again.
Again, Moby is correct in assuming that it is not timing, or all the compressions would be low. Clearances can be adjusted using shims under the tappets. These must be mic'd to ensure the proper dimension. The cam must be removed to change the shims. To ensure proper timing once the cam is replaced requires a "cam centering" tool. This tool comes in the tool kit that came with the car, or can be purchased at a Jaguar dealer (very expensive - $90), or a Jaguar after-market restorer (not so expensive - $20).
Posted on Nov 11, 2008
I would have thought that if the cam timing was out then the cylinder compressions would still all be roughly the same because they would all be out by the same degree.
The lowest cylinder is down by over 50% on the other 5, and I would say that the other 5 could be higher by at least double.
You could check the valve clearances as a first port of call, but without seeing the car for myself, I would say tha that the head needs to come back off for further investigation.
Posted on Jun 15, 2008
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Posted on Jan 02, 2017
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