TFSI Camshaft failure diagnosis+Pics - RE Fuel Pressure

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Ceebl

RMS Regular
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1,930
Location
Larne
Drives
330d/C2 Loeb
Thought I would put a bit of info up here for all TFSI and equivalent owners as I spent many days researching and trawling through manuals and ended up buying some parts for measurements and comparison etc.
Feel free to link this on to other GTI forums etc as you wish, I am not a member of many...

If you are suffering from low fuel pressure obviously check all the usual stuff first.
Get it logged on vagcom, get things like the duty cycle of the lift pump and the injectors checked.
Get the requested and actual pressures at the low and high pressure sensors checked out.
Replace your fuel filter if you are in any doubt but be ware there are several kinds rated to different pressures so make sure you also have the correct rated one for your car. If you are unsure give your chassis number to a VW dealer and let them supply you it would be the best bet.
What I was experiencing was the car seemed to run fine and made plenty of boost etc.
Normally started fine from cold but sometimes turned over a few more times than it should.
The only thing my car did differently was once it started to climb the revs and try and hold boost under any amount of load it would lose fuel pressure badly, like instead of 110bar it would drop down to 30bar.
At idle the car seems to sit around 40-45bar and if you accelerated nice and lightly the fuel pressure would creep up with the revs as expected. As soon as you went open throttle and the turbo came in the fuel pressure dropped away to nothing.
My car was under warranty at the start so it went through all the usual stuff people change when they have pressure issues on these; High pressure pump, return valve, thrust sensor, high pressure sensor, fuel filter were all changed and didn't really make any difference to the car.
I then looked into less common things that could be making me lose boost etc thinking that maybe I was having a strange issue that could be causing the turbo to over run and the engine was simply cutting boost and timing to compensate for something else so I set about replacing the diverter valve with a rev G and I deleted the PCV system.
This left me very little to look at in terms of the fuel system; lift pump or injectors, but I had a theory.
Everyone had so far looked at pressure but to me it seemed like a flow issue, to get pressure under a light load but then lose it suddenly when the injectors opened up flat out made me think I was drying the fuel rail out.
Firstly I got the lift pump logged to make sure it wasn't excessively worn (Ross-tech recommend a duty cycle of over 50% at idle should be considered for replacement as this indicates wear)
Also I wanted to confirm that the requested and actual low pressures matched even under this failure condition.
The duty on mine was just 50% but the requested and actual were spot on identical even when the high pressure dropped off and the car pulled timing completely and went into limp. This indicated to me that if it was a flow issue it was with the high pressure pump.
Given that the pump and its control sensors had been changed I figured it was something a computer couldn't tell you so I figured I would inspect the follower that went in with the new pump less than a year before now to see if there was any scary wear on the follower from a knackered shaft or if there was any visible damage to the shaft lobe itself.

Here is where the fun really starts.
The follower had a little wear in the centre but looked ok otherwise.
The shaft had a little wear visible but was hard to tell anything else, I set about measuring the high and low spots of the 3 faces of the fuel pump lobes by putting the car in 6th and rolling it back and forth to move the shaft, measured with the tail of a micrometer against a known part of the housing and compared the differences basically.
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When inspecting a follower and fuel pump it is important to look for damage to the case hardened follower, in my opinion the one I removed here would have been ok for a while yet but it is the area where the black coating is being worn away you need to keep an eye on.
When you have the HPFP removed its always worth inspecting the end of the stalk that rides on the follower for damage to see if it has been ran through a follower by a previous owner.
At this point I would strongly advise if you ever have any doubt about a follower change it.
If you ever destroy a follower and have a pump grind into the camshaft, replace the pump, follower and the camshaft at this point.

Do not try and cover it up as it will cause serious issues for the car and if it doesn't bite you it will take years off a future owners life...
As you can maybe see from the chalk writing on the bench we established a common low reading, this was a measurement from the engine cover to the follower when it was at its most inward point of the stroke. Then we turned the engine over manually and tried to take the 3 highest points on the cam. If you take the difference between these you can see the max lift of each lobe, mine was around 3.5mm. This does not show you the profile of the lift which is also important but its a good start. I haven't measured a new camshaft in place yet but I reckon this should be closer to 4.5mm
Although I could not see significant wear through my little inspection hole where the follower came out, I reckon what had happened to mine was it had worn badly by a follower failing before which had ground a trench into the lobes and then someone has just replaced a follower hoping for the best, this follower probably didn't last too long but it seems it just buffed all the material higher than the trench off, thereby polishing the cam face flat again, but around 1mm lower than it should be.
So next I pulled the cam chain cover off, this takes a bit of time and patience... (take the battery and batt box out it gives you much more clearance for this job)
I measured my old camshaft lobes for the pump in a triangular fashion, basically measuring the perpendicular height for the 3 lobes. This is the height from one flat face to the opposite point if you picture the triangle shape. These are also written on the bench measuring around 41.33-41.66mm across.
I then purchased a new Revision J inlet camshaft from VW (06F 109 101J from memory) but probably as well just giving them your chassis number then it is their fault if they supply the wrong part. Also interestingly found VW to be roughly the same price for this and a new follower as a few other local places I phoned up.
Was around £320 for the inlet shaft and follower.
My new shaft measured 42.53 across the perpendicular height which was good news but it was the difference in profiles that was seen while changing them surprised me most.
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The new Rev J is the one with the pressed on lobes, the old shaft is a Revision A which is a single piece and a known soft spot on the TFSI.
The difference now this is changed has transformed the car. Really pleased its done.
I would urge anyone suffering fuel pressure cuts to have a look at these measurements and checks and have a bash at measuring their own. None of these measurements were to be found online and VW were a lot less than willing to give me out any specs for my engine.
The changing of the shaft itself was done by Jonny at AI Autosport who I can't thank enough for his help and quick turnaround also.
Anyone needing any work done on these engines in the Carrickfergus area I would urge to PM him for a quote, you won't be upset! (I am not sponsored or involved in AI Autosport, just more often than not people only take to the internet to complain about businesses. I believe we should promote people who do a good job too!)
If anyone wishes to know any further details or doesn't understand some of the checks don't hesitate to drop me a pm.
I believe the revision A camshaft will only affect those with an early AXX engine code, however the overall rule applies that if a follower goes through and the HPFP drags on the camshaft it would be worth your while taking the cover off and measuring it and if it is at all damaged, take the hit and replace the inlet shaft. It will save you so much time and money down the line with diagnosing it when it does let go!
AI Autosport on here is @AIRFORCE1 I believe if you need to PM him...

Hope this info helps someone else and makes their job a bit easier than mine was!
Chris.
 
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