Member Since: 20 Jul 2015
Location: Here
Posts: 575
You can still get reasonable compression with spun lobes, for one, the rotation speed is different, for another, the amount of fresh air you're drawing in or the amount of burnt gases you're pushing out makes a difference to combustion, not so much to compression. Even a few degrees on one lobe will give poor running but the compression will be within tolerance.
21st Dec 2022 10:07 pm
jenseneverest
Member Since: 12 Jun 2017
Location: somewhere
Posts: 769
i think Mikey has nailed it, a few degrees of twist in a cam shaft would be enough to make it run really rough.
Edit Flatlander beat me to it
21st Dec 2022 10:20 pm
Mastertech
Member Since: 13 Apr 2014
Location: North East
Posts: 131
The smoke from the tail pipes is unburnt fuel, so as you have fitted and ruled out injectors your looking at a timing/ compression issue in my opinion.
Injection timing based on crankshaft position could be a possibility, but if the crank and cam sensors weren’t correlating I would expect a fault code to be stored and extended start up cranking, if it started at all.
If you have a mechanical timing issue then my first thought was as Mikey said, the lobes spinning on the camshaft but you’ve changed the one with the valve to piston contact so I would expect the others to be ok.
This leaves compression, what’s the specs on topix for compression on a 3.0 gen 2? Does it have good power once it’s on boost? Did you measure piston protrusion when replacing the head gasket’s?
21st Dec 2022 10:26 pm
rrhool
Member Since: 28 Aug 2014
Location: Norfolk
Posts: 4520
jenseneverest wrote:
i think Mikey has nailed it, a few degrees of twist in a cam shaft would be enough to make it run really rough.
Edit Flatlander beat me to it
rrhool wrote:
If it's had a valve strike, I wonder if one of the cams has a twist?
Richard
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21st Dec 2022 10:44 pm
Mastertech
Member Since: 13 Apr 2014
Location: North East
Posts: 131
Thing is you know which valves have hit the pistons as the rocker arms are the first part to be damaged. I’ve replaced rocker arms before that were smashed (all of bank one) and that engine ran mint after the repair, as he has replaced the cam that had the damaged rockers I don’t see a cam being damaged without rocker damage.
Unless I’ve miss understood the extent of the damage and more than just one cam/ bank had damage.
21st Dec 2022 10:54 pm
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
If a valve is 'trapped' against a piston and a cam continues to rotate briefly, that can leave the valve and follower undamaged but push the lobe round a couple of degrees - not enough to see by Mk.1 eyeball but measurable - or at least comparable.
21st Dec 2022 11:02 pm
Mastertech
Member Since: 13 Apr 2014
Location: North East
Posts: 131
I think the only way to know is to change the cams, it’s either as you say the lobes have moved or incorrect (too thick) head gasket sizing. In my opinion of course.
21st Dec 2022 11:21 pm
tzdisco4
Member Since: 12 Jan 2016
Location: Lower Saxony
Posts: 10
Hi,
maybe the rough fidling has to do with wrong fuel pump timing. AT least for the D4 3.0 Diesel engine the READ belt (rear end accessory drive belt) the positions of the cam and the pump must be timed.
Here a picture from the MY11 workshop manual showing the mounting position.
Click image to enlarge
This differs from the position shown on the photo of the first post.
Regards
Thomas
22nd Dec 2022 10:40 am
Fischirian
Member Since: 14 Aug 2022
Location: Osnabrück
Posts: 28
Wow, thanks for all your help man! This is so great and helps me a lot.
@Flatlander: Good to know. I will keep this in mind.
I want to drive some miles next week to check whats up with the engine. How it runs, smoke etc... I drove today but only 1 mile and the car was after that really smoking out of the exhaust (white smoke, it looked like water but smelled like unburnt diesel). I remember from my last 3.0 XF (2013 car) that it even smoked for a few miles really bat after the engine failure, until the unburnt fuel was burnt in the exhaust. Because of that i will drive some miles to check, if this gets better.
Click image to enlarge
@Mastertech: Injectors are really 99% ruled out. I replaced injectors and i even checked the timing of the high pressure pump, all fine.
Position of cam and crank must be fine because i got no error codes, nothing. Even after the mile i drove today there was no error code, nothing.
The power of the engine seems not bad but i drove it careful today because i don`t want to full throttle the complete new rebuild engine, especially with the poor engine run at the moment.
I measured Piston Protusion and went for a head gasket with 4 noses, this type of gasket was even installed on the engine before. I didn`t surfaced block or heads because the flatness was under 0.05mm.
When i disassembled the engine i saw only cracked followers/rockers on the right head @ the exhaust cam, which is connected to the timing belt. I replace this camshaft because it was damaged as you can see on the pictures on page one. The pistons on that bank had slight marks of the exhaust valves, but also slight marks of the inlet valves. The inlet valves were even slighy bent and i replaced them. I didn`t replace the inlet camshaft because it looked fine. Maybe here is the mistake, maybe this cam is out of timing due to rotated lobes...
@tzdisco4 timing of the high pressure pump is 100% right, i double checked yesterday. It was on point.
22nd Dec 2022 10:38 pm
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
Bear in mind the plausibility of the CKP / CMP relationship is (with regard to the Camshafts) to the position of the core of the camshaft and not the lobes, there is no check of the inlet/outlet phasing either.
You should be able to do a basic check of the camshaft lobe positions by marking a line from the axis of the camshaft to the centre of the high point, rotating the engine and comparing the relationship bank to bank. Not a quick job but should give you a rough idea if there is anything requiring further investigation.
22nd Dec 2022 11:02 pm
Fischirian
Member Since: 14 Aug 2022
Location: Osnabrück
Posts: 28
Thanks for your help guys, i was able to fix the problem!
It was a damaged/stuck injector.
When i started the engine first after rebuild, i had really bad idle as you can see in the video. I immediately changed the injectors again a second set i had from another engine (not tested but seller told me this engine was pretty fine).
After installing these set of injectors i had the same bad idle, so i thought of compression/timing/etc., all what we discussed here.
Last week i went on with troubleshooting and i was pretty sure it could not be timing because i worked here really certain.
I let the engine again idle and disconnected one injector after another and plugged it back in. On Cyl 1, 2, 3, 4 and 6 the idle went again significantly worse, only on Cyl 5 was almost no difference between plugged in or plugged out.
I changed it with another injectors from the previous engine and suddenly the engine and idle were perfect. No more smoking out of the exhaust, good power, etc.
I am pretty happy that you helped me and i appeciate this. In the end it was just an injector and i feel a little bit dumb but this is really random, that in 2 sets of injectors there is each one bad injector that causes the same bad idle...
4th Jan 2023 7:33 am
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
That's really bad luck!
Glad you got it resolved in the end.
Be careful disconnecting piezo injectors with the engine running, they can stick open if disconnected at the wrong time...
4th Jan 2023 3:23 pm
Mastertech
Member Since: 13 Apr 2014
Location: North East
Posts: 131
I think this shows that it’s better to have injectors tested properly by a reputable company than blindly change full sets. I’m glad you got it sorted in the end though without pulling the engine apart again. Thanks for the update.
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