One reason why fuel-rail pressure may be low....

[ROH ECHT]

I found the pic below and cleaned up the specs to be more legible. Hoping for confirmation on the dimensions as well. I will leave it posted for future use when others are struggling to find why the rail pressure is suffering. As this may be the reason for it...given the age of our MK5 today.

This pic is supposedly of the intake cam tri-lobe; found on std-K03/BPY (and the like; AXX_BWA_etc.) of the EA113 engine. Remember, or know, what is important to produce rail pressure is the cam lift...in other words; the travel/stroke of the piston inside the HPFP.

As we know, the K04 equipped cars have intake cams with a bit more cam lift on the tri-lobe.

Also, take a look and if you can confirm the specs in the pic, just comment below please.

[breeze]

I have started to look at the cam lobe, follower and even the HPFP plunger tip on these cars as wear items.

On my car, rail pressure was perfect when standard but when running a stage one map it was possible to get rail pressure dropping briefly in 4th gear under very particular conditions. IIRC around 3.5k at full throttle. Very rarely it would log a fault code too. Felt like the kind of thing I would have ignored without logging.

When I disassembled I found wear on the lobe, follower and plunger. Not a massive amount and at 145k I am sure would have been fine indefinitely with the standard map.

Classic dealer solution is to renew everything with standard parts. Partly because the I am thinking about future upgrades, I chose to do Autotech HPFP internals and a new follower to see whether that would be enough. Cam replacement is a much more complex and more time consuming job. Result was fuel pressure is now perfect, under all conditions.

I think we will all have wear at different stages across lobe, follower and plunger in these cars, but I’d say your lobe would need to be very worn if you have issues with new HPFP internals and follower.

[ROH ECHT]

This all is likely only going to be helpful to those who've picked up their MK5 second, third, or fourth hand. Where the previous owner/s neglected all this, as well as informing the next owner. I've recently been helping a few with the issue. They've replaced all they could think of, only to find out the intake cam needed replacing. When they measured the tri-lobe 42.5mm, theirs was between 1.5mm to 2mm shy. There wasn't as much wear at the 3.5mm spot, so it was all worn at the peaks...thus reducing the cam lift and stroke of the HPFP's piston.

I thought if I posted this pic, perhaps some would then see it come up on one of their searches. And perhaps they would check the tri-lobe before replacing a list of fueling parts.

[breeze]

Understood, yes it is good information to share.

My understanding was that the earlier intake cams were very prone to early wear but they were revised during production of the BWA. My car as a 2006 has an early cam. At 145k I thought a little wear was OK. I was looking at replacing the intake but in the end didn’t need it. You actually responded to one of my messages on the ‘tex. 

As an aside, there is a way of replacing the intake cam without touching the cambelt or exhaust cam. That simplifies things massively, particularly if you have a recent cambelt and the adjuster performance is in spec. That was my backup plan.

https://www.audizine.com/forum/showthread.php/572832-2-0T-Intake-Cam-replacement

[rich83]

Great info. Shame it’s impossible to measure without stripping the chain cover.

[ROH ECHT]

Great info. Shame it’s impossible to measure without stripping the chain cover.

Right...measuring of it, might just be something to add when doing the timing chain, tensioner, and oil containment ring job.

[breeze]

I think the drop of actual vs specified fuel rail pressure at around 3,500 RPM is the big giveaway. At that point it is likely to something on the high pressure side of the fuel system because that is mechanically linked to engine speed.

You can remove the HPFP to check plunger and follower fairly easily. If they look OK then there is a good case for removing the chain cover and measuring the cam.

Taking the opportunity to measure when replacing the chain would also make sense.

[LC5F]

Great information.
I was thinking you could remove the HPFP and use calipers to measure the depth from of lobe to shaft.
- or -
Would whipping just the vacuum pump off give enough room to measure?
it would make an ideal time to re-new the pump seals at the same time

[ROH ECHT]

Great information.
I was thinking you could remove the HPFP and use calipers to measure the depth from of lobe to shaft.
- or -
Would whipping just the vacuum pump off give enough room to measure?
it would make an ideal time to re-new the pump seals at the same time

That is a really good idea. I think it is definitely something worth attempting, if to avoid removing the chain cover. Some calipers may make the reach while some may not, but....so long as cam lift measuring is achieved; 8.75mm - 3.50mm = 5.25mm

[pudding]

Or you could use a vernier caliper's depth measurement from the machined surface of the HPFP hole, to the peak of the cam.  We would of course need a known good measurement as a reference first.

Regarding K04 cams, apparently only the CDL (plus all 265hp derivatives) shows a different intake cam on ETKA.  AXX, BWA, BYD etc all share the same cams.

Cam wear certainly makes a lot of sense for explaining fuelling short falls.  But it's not quite as clear cut as that unfortunately as there have been several revisions of HPFP over the years.  Some can support Stage 1 and higher with ease, and some are borderline even on stock fuel demands.

If it were me, personally I wouldn't waste my time just replacing 1 cam.   This is a far better option, and everything is new.  Cams, guides, valves, VVT gear, the lot.  Slap it on and move on with your life    It's a similar price from VW directly last time I enquired.

https://tornau-motoren.de/en/NEW-Cylinder-Head-complete-for-Seat-2-0-TFSI-BWJ-06F103063PX-240HP-177kW/p/detail/10015215

[ROH ECHT]

That is another good idea for checking cam lift.
One would only need to measure depth and then rotate the engine to measure the two spots required to figure the lift...thank you.

With a sturdy bit of straight edge to span the HPFP opening, one could use the depth-end of their typical/std calipers;

[rich83]

A proper depth micrometer would work better.  Good idea pudding. I would think measuring off that face would be fairly accurate.

[G-olf]

Do you guys mean a dial gauge? mounted where the pump fixes, then through the hole where the plunger goes. Turn the engine by hand, watch the dial move as it follows the cam lobe?? Therefore measuring the lift on all 3 lobes

[pudding]

Yep.  Although most dial gauges have a magnetic base, so you might struggle to find enough steel in the area to mount it to.  Although, I suppose you could gaffer tape it to the rocker cover!

We're only looking for mm measurements, not 1000th/s of an inch, so any old cheap gauge/caliper should do the trick.

I'm not sure how thick the DLC coating is on the follower, but once that's all worn off, that won't be helping with the pump lift either. 

It's clearly a very sensitive setup if 1mm wear is enough to cause fuel pressure drops.  You would therefore hope the chain cover is a consistent and accurately machined part on all engines, hence using it as a reference point 

I suppose you could even drop a brand new follower down the hole and just stick your chosen measuring device into that, then rotate the engine and note down the lift on each lobe.  Even easier!

[adamvaughan]

What sort of mileage would you expect the cam follower (and other parts?) to last for? My BWA engine has done just over 56k and I doubt it's ever been replaced.