P0340 code after Head gasket replacement

[Mechanic-al]

In that case, if it's not adjustable, we can discount that as the cause of the problem.
Are there tensioners on both runs of the chain from the crank sprocket to the cams? If so, do they both appear to be doing their job? One deflecting the chain more than it should, at the expense of the other, will affect the cam timing.

Excellent question, I love the way you're thinking outside the box.
There is what I would call 'aligner' and one tensioner.
When looking at the front of the engine, it rotates CW (Clockwise).
The exhaust camshaft (with sensor) is on the left and the chain runs in a perfectly straight line down to the crankshaft.
This tensions the chain over both crankshafts and the crankshaft, ensuring no tensioner is required to 'time' them.
The tensioner is on the slack (return) side between the crankshaft and inlet camshaft.

 

[brianmoooore]

Difficult to see how anything could go wrong with that tensioner arrangement that would affect the phasing of crank and cam.
Clutching at straws now. The crank sprocket appears to be separate from the crank. How is it located on the crank?
Presumably there are timing marks on each cam pulley. What/where is the crank timing mark?

 

[Mechanic-al]

Difficult to see how anything could go wrong with that tensioner arrangement that would affect the phasing of crank and cam.
Clutching at straws now. The crank sprocket appears to be separate from the crank. How is it located on the crank?
Presumably there are timing marks on each cam pulley. What/where is the crank timing mark?

Hi,
The crank sprocket appeared to be an integral part of the crankshaft. I tugged on it a bit and it didn't budge so I left it alone.
Re-assembly instruction include reference to coloured links. A silver one aligns with a dot on the crank sprocket and blue ones align with markers on the cams. Also other marks on the cams and head to ensure alignment is correct.
After re-assembly the engine was given somewhere between 10-20 revs until the chain links realigned with the marks on the crank and cams. All seemed A-OK at the time when I replaced the timing cover.

 

[brianmoooore]

Only thing I can think of now is to check that the crank timing mark really does correspond to TDC. This is normally possible to check with a dial gauge, through #1 spark plug hole, onto the top of the piston. Check that the crank mark corresponds to the piston at its highest point.

 

[Mechanic-al]

Only thing I can think of now is to check that the crank timing mark really does correspond to TDC. This is normally possible to check with a dial gauge, through #1 spark plug hole, onto the top of the piston. Check that the crank mark corresponds to the piston at its highest point.

Good call.
I don't have a dial indicator, but I once did this check on a 2 cylinder bike engine with a screw-driver down the plug hole. It worked a treat.
I was about to ask which is the #1 cylinder but since it's going to be at one or other end, and both those crank journals are at the same angle, it doesn't actually matter.

 

[brianmoooore]

You won't get the accuracy required without a dial gauge. The movement of the piston a few degrees either side of TDC is extremely small, and you need to establish exactly where TDC is.
Cylinder #1 is usually, with the odd exception, the cylinder nearest the crank pulley, but, as you say, the one the other end is usually its twin.

 

[Mechanic-al]

You won't get the accuracy required without a dial gauge. The movement of the piston a few degrees either side of TDC is extremely small, and you need to establish exactly where TDC is.
Cylinder #1 is usually, with the odd exception, the cylinder nearest the crank pulley, but, as you say, the one the other end is usually its twin.

Noted and understood.
What concerns me is that if I do find the crank marking doesn't match with TDC, but the manual says it should, something is wrong but it must've come from the factory like that. And then how was I ever expected to get the job done as per the manual ?
Does this kind of thing happen often?
As an amateur, I'm sure you understand my anxiety.

 

[brianmoooore]

Zooming in on the crank sprocket in your diagram of the chain and tensioners, it looks like its located by a woodruff key. Extremely unusual, but these can wear and partially shear, which would throw the cam/crank phasing out.
The fact remains that there is a problem that the ECU is unhappy with. Have you tried any owner's forums online? Sometimes it appens that what appears to be a very obscure fault is well known amongst those familiar with that model.

 

[Mechanic-al]

Zooming in on the crank sprocket in your diagram of the chain and tensioners, it looks like its located by a woodruff key. Extremely unusual, but these can wear and partially shear, which would throw the cam/crank phasing out.
The fact remains that there is a problem that the ECU is unhappy with. Have you tried any owner's forums online? Sometimes it appens that what appears to be a very obscure fault is well known amongst those familiar with that model.

Hi,
I saw no deformation on the woodruff key.
Unfortunately, I came here due to the owners forums being very suspiciously silent on this topic.
I agree that something is definitely wrong somewhere, And it's GOT to be something I've done !
I think the summary so far is that it's either wiring / ECU or timing.
So on the face of it I haven't made much progress but in fact it's been a fantastic education for all you guys' input.
I am extremely grateful for you taking the time to help me learn.
I've now got a list of things to check so I'm going to stop bothering you and go and get the checks done.

In order of difficulty...

Electrical checks:
CMP sensor earth.
Signal breaks when engine is manually rotated.
Scope signal and verify waveform.

Mechanical checks:
Crank sprocket marking / crank (woodruff key damage).
Crank sprocket on crank / TDC.
Timing OK?
Cam sprocket positions on cams.
I'll be back to update you asap.

Thanks again guys, I'm in your debt.

 

[OnlQQker]

6:04 on the video might shine a light

 

[Mechanic-al]

6:04 on the video might shine a light

Hi,
Thanks for investing your time here.
Very interesting clip, I laugh at the fact that an electrical issue elsewhere can throw up the rather specific and unrelated P0340 code. That's why Auto-electricians should be known as Auto-electric-magicians.

Without a scope, I'll have to cover the 'cheap / free' checks before I pay someone else to scope the system.
The alternator was new last winter, although I am aware that doesn't mean it's good now.
I'll add it to the list and get to it in turn.

Thanks again.

 

[brianmoooore]

Good call from OnlQQker. Modern car electronics are dependant on a good, clean and stable power supply.
I have a BMW 118d in the workshop at the moment, which has been laid up, unused, for 3 years. Apparently good battery fitted, and although it cranked OK, it showed no sign of starting. Instrument panel warning lights lit up like a Christmas tree. Read all the fault codes, cleared them, and cranked again. Connected the scanner again, and got all sorts of codes - a couple from the engine ECU (fuel pressure related), and loads more from all over the car, and the warning lights back.
Changed the battery for the 100A deep discharge one from my caravan, and the engine coughed and spluttered into life. Cleared the codes, the engine ones cleared for good, along with most of the body modules codes, and no warning lights.

 

[DPG]

Good call from OnlQQker. Modern car electronics are dependant on a good, clean and stable power supply.
I have a BMW 118d in the workshop at the moment, which has been laid up, unused, for 3 years. Apparently good battery fitted, and although it cranked OK, it showed no sign of starting. Instrument panel warning lights lit up like a Christmas tree. Read all the fault codes, cleared them, and cranked again. Connected the scanner again, and got all sorts of codes - a couple from the engine ECU (fuel pressure related), and loads more from all over the car, and the warning lights back.
Changed the battery for the 100A deep discharge one from my caravan, and the engine coughed and spluttered into life. Cleared the codes, the engine ones cleared for good, along with most of the body modules codes, and no warning lights.

Indeed. This is also a common cause of faults on Jaguars. A good example is the car showing 'Gearbox fault', but actually the battery voltage is low. Sometimes the gearbox warning can show instead of the low battery warning.

Having said that, I suspect the issue on my XF is the gear change module. Seems to happen in cold weather and I think I'm going to have to delve into the centre console.