T4 TDi suddenly very noisy

[gldgti]

The timing signal read in VCDS comes from the 5th injector, which has a needle lift sensor. This is what supplies the timing data to the ECU.

If the timing control piston is/was seized, this is the likely cause of your problem. The little valve with the wire coming off it to the right of frame on your first photo is (i think) what the ECU uses to modulate the fine control over the timing. I think that valve bleeds pressure from the pressure side of the piston in order to retard the timing from the basic setting. However in my experience (and according to theory) the extent of control afforded by this valve is not significant, perhaps 2-3 degrees of timing (enough to change the diesel rattle, and affect emissions though).

The timing ring in the pump should not seize in my opinion, based on the design of the pump.

When you set the basic timing, how are you doing that? are you just aligning timing marks or are you measuring cam plate lift at TDC using a dial gauge in the back of the pump?

*** Edit***
Another thought I just had - if the fuel pressure in the pump is too high, this may be causing or adding to the problem. It seems unlikely that this would be the case, as the design of the fuel pressure regulator is robust and should not fail upwards (if that makes sense). However, if the return flow from the pump is restricted (like the return barb has been crimped or bent) enough, this would result in too much pressure and too much advance. Just something worth checking.

If you want to call me to discuss I have PM's you my phone number.

[farmsyncro]

Update:

Following gldgti's comments I have disconnected the N108 solenoid to disable any function, good bad or otherwise. I have then tried to find a timing point where the engine will operate quietly (as normal).

I adjusted the timing several times by releasing the Injection Pump (IP) drive sprocket on the camshaft and rotating the IP very slightly before re tightening the cam sprocket. Each adjustment I monitored with VAGCOM.

I have had the timing set from 1 ATDC to 19 BTDC on measure blocks "actual injection timing".

At no point was the engine its normal quiet self! At 1 ATDC it was hard to start as you would expect which indicates to me that the "measurement" is probably correct.

Now I think there must be a IP problem. I am not familiar with these so I can't see the sense in disassembling it as I do not know what I would be looking for. The quotes I have been given to recondition the IP are from $2k up and I never got a straight answer if they can fully test the N108 function.

Yes, I am still convinced it is "diesel rattle" and not some other mechanical noise.

I have a s/h pump in transit from a very kind VWWatercooled member and a "plan C" s/h pump at a wrecker on standby.

The fact that cycling N108 in VAGCOM has no effect still bugs me. The fact that this started one morning on cold start still bugs me.



Does anyone have any other thoughts or suggestions on what could cause this?

Farmsyncro

[gldgti]

Can you take a video of it running and post it on youtube for me?

[farmsyncro]

Can you take a video of it running and post it on youtube for me?

That will test my capabilities but Yes, I'll try.

[gldgti]

Leaking injector is about the only other thing I can think of that might cause a similar issue. You could test that by loosening injector unions one by one as its running and listening for any change in the sound as each one drops out.

[farmsyncro]

Here are a couple of YouTube links of the noise:
YouTube
YouTube

I now have a s/h Injection pump so I will try this and see what happens.

Also, someone in the UK forum has suggested (insisted) checking the cam timing. I haven't actually done this, I have checked the belt for soundness and that was fine. I will check this when I replace the IP.

I will get the injectors tested however, I am keen to try the bigger nozzles as mentioned in the "Project Power" thread and discussion in the UK forum.
Has anyone used these nozzles?
Can anyone recommend a good company/person to remap?

Cheers,

Farmsyncro

[farmsyncro]

Here are a couple of YouTube links of the noise:
YouTube
YouTube

I now have a s/h Injection pump so I will try this and see what happens.

Also, someone in the UK forum has suggested (insisted) checking the cam timing. I haven't actually done this, I have checked the belt for soundness and that was fine. I will check this when I replace the IP.

I will get the injectors tested however, I am keen to try the bigger nozzles as mentioned in the "Project Power" thread and discussion in the UK forum.
Has anyone used these nozzles?
Can anyone recommend a good company/person to remap?

Cheers,

Farmsyncro

Update:

The pump is on & ready to go. I also took the opportunity to remove the IP drive pulley from the end of the camshaft to check the cam timing. This is advanced! This explains my advanced Injection timing! I'm not convinced it is a whole tooth advanced but I have to try correcting this. I estimate a tooth to be 9 deg. CAM movement.

When I have removed the Cam belt covers, the drive pulley & harmonic balancer and covers, I find the tensioner looks a bit dodgy. Pulling the belt moves the tensioner & I do not remember this being the case before. Removal of the tensioner reveals that it has broken a piece off the housing and closer inspection of the belt shows a small cut to the edge, probably where the tensioner part was spat out.
If the tensioner is not functioning correctly the belt may be able to hop a tooth.....

I will source a belt kit, assemble it, set the cam timing, set the IP timing and see what happens.


Now I MAY have to eat humble pie about my opinion of the noise being "diesel noise"! That will be hard.


Farmsyncro

[gldgti]

Oh dear!

It sounds like valves kissing piston crowns to me

If you can beg borrow or steal a borescope inspection camera thing, you may be able to confirm this by removing an injector or a glow plug and having a look at a piston crown.

Also just turning it over by hand you might be able to feel it when they touch. Hopefully not too bad.

My grandads mk1 GLD had valves kissing pistons for years.... nothing ever went wrong with it.

I guess if this is the case and the contact doesnt look too bad, you might consider putting some new lifters in it and be done with it.

[farmsyncro]

Oh, the sounds of silence.


The cam belt tensioner had failed and parts of the alloy base & pointer had broken away. I assume this has nicked the belt on the way out although this is only a minor cut on the edge. The main problem is that the spring that engages the inner rotating part of the tensioner has broken so there is no spring pressure to tension the belt. When the engine has been turned off and bounced backwards on compression it has tensioned the slack side of the belt and the tensioner has not held the belt length enabling it to hop a tooth advanced.

So this explains the noise (most likely minor 'knitting') and the advanced injection timing that I found.

I failed to actually check the camshaft timing early! This would have saved a whole lot of time. I had checked the cam belt by removing the top cover and having a good look over the belt and finding it was tight. I then assumed it was not a problem here.
Checking the cam timing involves removing the IP drive pulley and inserting the plate in the slot in the end of the camshaft. Because this is a backwards step creating more work to reset the IP timing I had not gone here early. Now I/we know.

It is all back together now and quiet as a mouse (as far as a T4 ACV can be). Performance seems fine, fuel consumption check will come with time- this is a very good indication if the efficiency is still good.

Thank you to all who have contributed. It has been a frustrating repair.


FarmSyncro

[02mick]

Hi everyone, im not sure if this is bad practice, if so i do apologize and please disregard.

We have a '99 tdi with an acv engine as wel we bought it roughly 6 years ago, it has an intermitting idle issue, at times it works fine and other times it idle irregularly, not even hunting but bouncing between 700 and say 900 rpm. There seems to be no rhyme or reason to when it does this. Its been to two Volkswagen specialists (in W.A.) and neither of them could find anything wrong with the engine, I know one checked injection timing and i suppose they read codes ). when we bought the car I bought 2 Bentley manuals but.. the fuel system as it is in this vehicle isn't covered by the book ( that was a good 450 dollars spend there !)

I have a bitt of time on my hands and would like to see if I can get this sorted. I have tried to search for info on the idle circuit or on the controls of the pump and pump alone but haven't had much luck, can any here point me to the some use diagrams or other info of the fuel system of this particular model ?
Any links or info is much appreciated, thanks Mick.