Valve Lift Solenoids and Testing Activations - What should we see?

Thought I'd create a new thread as this is starting to get more specific from my original thread here: https://911uk.com/porsche/996-turbo-fuel-pump-alternatives-not-required-other-causes.131138/ Slowly chasing down the reason why the 996 Turbo is not making power or able to rev post engine rebuild. In the above thread, there is a link to a video which shows several potentials, and although I am leaning towards the incorrect orientation of the cam box gasket(s), before I get into removal and stripping I want to rule out all other possibilities. To recap, at idle, with Durametric plugged in, when revved, the cam angles change at 3k rpm, but when driving, once at 3k, the engine registered various misfires on all cylinders on bank 2. The car struggles to rev past 4k and is very sluggish. When activating the "valve lift control bank 1 and 2" on the Durametric at idle, there was no change in engine note which is not correct as Mac996t kindly verified with his own car. So this leaves me with one of three potential scenarios. The valve lift solenoid is faulty, the message from the ECU to solenoid is faulty or the gasket orientation is wrong preventing the oil flow to the hydraulic tappets. So, starting with bank 2, I have knocked a basic test light which I can plug into the loom plug for the solenoid, and with this in, and the solenoid activated via Durametric, the bulb will flash on for a second, then off for a second, continuously until I select stop on the Durametric. This does it regardless of which option I select on Durametric, weirdly there are two options which say the same. So the first question is, why is the bulb flashing on and off, and not constant? Is it supposed to do that via the Durametric? With nothing activated, when I rev the car at standstill, the light doesn't illuminate when revs get to 3k. Now I'm pretty sure the valve lift only works once the oil is up to temperature, but not sure what that is? mine was around 65-70 degs when tested. I was expecting to see it light up at 3k. Should it? Haven't got any further so far as it all gets a bit hot to do anything for a while, but would appreciate some advice on what I should be seeing before jumping to conclusions and going down the wrong 'rabbit hole'.

First thoughts, you'd think even turning on for 1 second would be enough to do something!. Are you testing with the solenoid connected (lamp piggybacked), or is that with your lamp on the end of the disconnected connector, if so don't know if that maybe affecting it. It sounds like you've managed to remove the connector, can you get a meter in there to at least check the solenoids have the same resistance side to side and are not open circuit. I know it's a bit of work but I'd remove the bumper, intercoolers and heat shields and pull the solenoids and inspect then and the oil ways looking for sealant etc, and that the springs are present and correct, then test them with 12v off the car. I'd also swop them from side to side. I don't know if the durametric will activate them if they are removed from the heads but plugged in to the connectors and the engine isn't running,it'd be worth seeing if they will activate via durametric with the ignition on while you've got it apart. This may reveal that they are energising! Have you compared the other readings I posted in the other thread, some pics of those might be helpful. You can't rule out that it's not some other parameter that's stopping them activating, the more you check the more you can rule out, and sometimes you notice other things which can sent you down a different path! Something else that was on my mind from the previous thread was that you only had misfires on one side, so why didn't the other side work via durametric?? Mac

Just thought of something else to possibly try if you can get to the solenoid plug without taking it all apart. If you go for a drive with the connector / connectors off, see if you get a code for open circuit solenoids. The other thing to try is rigging up your own supply with some spade connectors and see if tickover changes with 12v manually applied!

Thanks Mac. Some good things to try. Access is really poor with everything in place. I could just about get the plug off the solenoids and attached the test light to it without it on the solenoid. Access is better with the intercoolers off, but then I can’t run it up, so I want to try what I can with things in place at the moment. I like the idea of applying my own power to the solenoid which I think I’ll try next before taking them out and checking them. I was also puzzled by the fact the misfires were only one side despite no audible change when activated via Durametric. I’ll report back when I get a chance.

Currently suspect an intermittent fault on one of my valve timing solenoids so there's some useful information in this thread - thanks for your contributions! Did you manage to get the issue resolved rgracin?

If the engine revs fine at idle but misfires under load, that is often when VarioCam Plus should be switching to high lift but isn’t. That symptom lines up extremely well with oil not reaching the switching tappets. Which means your gasket orientation suspicion may actually be more accurate than you think. The single parameter that removes most of the guesswork is the VarioCam Plus switching status. In Durametric it normally appears as something close to: “Valve Lift Control Bank 1 / Bank 2” or “VarioCam Plus Switching Status” (Some versions show it as “High Lift Activation”.) You need to log this while driving, not just at idle. You reported two key things: - cam angles change at 3k rpm - no engine note change when activating valve lift Cam timing and valve lift are two different parts of VarioCam Plus. So your cam timing working does not prove the valve lift system is working.

On Mezger rebuilds where this symptom appears, the most common cause is oil flow to the VarioCam Plus switching circuit being blocked. That can happen from: excess sealant / incorrect cam carrier gasket / debris in the oil gallery Which is exactly the suspicion you already raised. The rebuild mistake that produces almost exactly the symptoms described on a 996 Turbo Mezger engine is installing the cam carrier (cam box) gasket the wrong way round or mis-aligned so it blocks the VarioCam Plus oil feed.

Apologies for the radio silence, been a bit busy. I'm currently in the process of pulling the engine again! I managed to use the bore scope camera to check the cam box gasket in situ. The part number is handily stamped on an area of the gasket that protrudes the cam box. Still couldn't get to see bank 2, but managed to get a look at bank 1 gasket part number, and sure enough, its the number for bank 2!! So it's this that's stopping the oil flow for the high lift.

Just thought I post a quick update. Pulled the engine and had new cam box gaskets installed in the correct orientation, put engine back in, and she revs and has boost! forgot how well the car goes as it's been so long. Just got some slight hesitation/jerkyness at very light throttle openings which I need to investigate, but otherwise runs really well.

Nice one, you got there in the end, took a while, just think of all the miles you've saved. Now get some use out of it while the weather still holds. Good to know you can see the gasket number and confirm it's in the wrong place before taking it apart, can I ask how you found that out?

Actually, it was thanks to you Mac! A massive thanks to you!! I watched the video you posted in the previous thread a million times, and concluded that if I removed the lift solenoid, and looked deep into the hole I would either see silver cam box (correct) or black gasket (incorrect). I happened to post that in the comments on the video, and within an hour or so, the chap who made the video from Protomotive in the US replied and told me the stamped part number can be seen from the outside. I did the I did both, and both worked and confirmed my worst fears. To see where the part number protudes whilst the engine is in situ, you need a bore scope type camera to get to it. You can see in the picture below it says "TOP 4 - 6" So numbers facing outwards which is correct, but this was on bank 1-3! The chap from Protomotive was really helpful and replied very quickly to several questions. Couldn't recommend them enough. Just a shame they're a bit far away. View attachment 160545

Great result! I've heard good things about Protomotive.