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😄 It's time to binge watch this thing so I can at least get to the end of it all... Hoping for a nice Hollywood ending where they all lived happily after all.
First drive went fine for a few minutes, before the pressure dropped again. Luckily the car did not stall and kept running okay so I could drive back to my house.
Reading the codes gave me a big scare as there was a list of about 50 CAN communication errors, until I realised that I swapped the ECU and had not yet deleted any codes. There are a couple of codes that will require some further examination, however the most interesting ones on the ECM (ME) where:
P0003000: The quantity valve has a short circuit to ground. Current and Stored. <- This must be the reason why the pressure dropped from 200bar to ~5bar, the ECU must be detecting a wiring issue to the QV, disabling it.
P1D2A09: At least one defective seal pack was detected. There is a component fault. Stored <- Absolutely clueless on this one, nothing I can find on google or WIS.
That first code should now be pretty straightforward to check, I'll get my test lamp out and see what gives. That second code is a big mystery, no idea yet what to do with that one.
I can't find the DTC P1D2A09 in my ECM DTC list, ours being the same MED177 ( although mine is a 3.0Turbo ) I would think it should have it in its ECM database.
So can we come to a more firm conclusion that your main issue is electrical ? I mean not mechanical like blocked fuel rail or camshaft tone wheel shifted.
This wont be fun, if you have to test your ECM wiring assy again and be extra detailed....but that seems to be what you need to do.
Weird, can't find anything on that DTC. The only reasonable hint I could find was a seal stack used to seal the injectors. Perhaps fluctuations in the fuel pressure can lead to spurious readings on some injector values, leading to this error? Of course, there is no way to know right now if this is an error on it's own, or if it's a symptom from another error (cause or effect cannot be determined in this state).
So can we come to a more firm conclusion that your main issue is electrical ? I mean not mechanical like blocked fuel rail or camshaft tone wheel shifted.
The fact that it ran okay for a few minutes seems to confirm that most parts are in good order. For now, this would rule out any issue with the cams, the ecu, crankshaft sensor, cam timing, the low pressure fuel side, the injectors themselves and the fuel lines. That's a lot that's now 'known good'.
Let's see if I can replicate the failure. At this moment, I cannot find a clear 'short to ground' with a test light (back)probing the ECU connector pins to the quantity valve. Strangely enough, getting 12V with my test light on pin 5 (+ signal to Y94), with ignition off, triggers the fan to come on.
Anyway, some better testing is needed of course. Stay tuned..
Short version: The terminals on the main engine loom in the connector to the Quantity Valve where opened up too far, leading to loss of contact / conductivity. I crimped on new terminals (luckily I had the right ones), and all is fine now!
Longer version: the P0003000 code was very helpful, as it indicated a wiring problem on the leads to the quantity valve. I started out with probing the ECU connector and check the PWM signal going to the quantity valve. The signal was there during cranking but stopped as soon as the engine started, see these captures:
The ECU logic seems to be as follows: During cranking, the ECU tries to control the quantity valve. After no result and/or unexpected signals on the driver in the ECU, it decides to give up controlling the valve. There are regular very short spikes, roughly every 3 crank rotations. I guess these spikes are there to check if the QV has come back. At the same time, the ECU generates the DTC for a circuit failure to the quantity valve. Once this DTC is set, the ECU will not re-attempt the PWM signal on startup, only after clearing the codes the ECU tries again.
I once again removed the intake manifold (got that down to 2 minutes now ;-)), crash plate on the HPFP and disconnected enough wires to make sure I could reach the connector to the quantity valve. Man, that connector is well hidden away..
Measuring the resistance on the circuit from the ECU connector, I could see that I had basically an open loop. Previously I was able to measure the coil resistance of the quantity valve at 0.5Ohm. So I roughly knew what to look for.
I rumbled around with the wires and could see the resistance to start moving about. Bingo. Eventually I narrowed this down to the Bosch connector on the HPFP. Wiggling that connector gave various resistance readings, all the way down to 0.9 Ohm. I decided to disconnect the connector (which is a pain) and examine things. And that's when I saw the terminal spades were wide open, almost 1.5mm. Once that was diagnosed, it was straightforward to replace the terminals.
For now my best guess is that the multiple handlings of this connector eventually made it fail. Keep in mind that the car got a new engine loom this year due to oil leaking into the harness. So this connector is less than a year on the car. However, after that time, the crank sensor has been replaced and work has been done in that area. Remember that on the original HPFP, the connector itself was broken off and clumsily repaired with epoxy. Then after all this, I must have removed this connector at least 5 times, so it's no surprise that by now it was showing serious wear.
Anyway, I went for a 20 minute drive which was all fine. I did get some new DTC's on the NOX sensor, let's see if that's intermittent. From reading the forum, it's no surprise that this sensor might be defect. Then again, a lot of unburnt petrol has accumulated in the exhaust which needs to burn out.
Furthermore, I get some loud clonking noises from the airmatic suspension on uneven roads and speed bumps while driving slow. Out on proper roads it's all very quiet and civilised. I guess some more issues will pop-up once I start using the car, after all it's a 10 year old car which has driven 60.0000 miles.
All in all this was quite an adventure. A steep learning curve, some moments of dispair and ultimately a happy ending it seems!
🤣
I've had my head under the bonnet for a lot of hours by now, and I'm sure I've not found any of those yet. I'll ask my MB dealer how many are needed for my model..
Jeedie,
I think we discuss much earlier on the subject of pin/terminal fitment test.
I think so too, and I did check various connections. I was able to measure the 0.5Ohm resistance before from the ECU side. And there is the fact that up until this week, the car always built pressure during cranking, but the pressure dropped off as soon as the engine ran. And on top of that, I did use a screwdriver-stethoscope to compare the sound of the HPFP with the QV in connected and disconnected state. There was a very clear distinction between the two.
What might have happened is that the terminals connected, but not in a fully engaged way. There is a relatively high current through the solenoid, at least 8A from what I checked on my bench. If only one of the terminals barely connected, that might have caused all kinds of undefined behaviour with the QV.
Typical female* ( *worse, weaker ) and male terminal, if tin coated only no silver, its data sheet guarantee good fitment up to 20-30 insert/remove cycle.
The silver coated one would be close to 50 cycles. https://mbworld.org/forums/e-class-w...onnectors.html
By the way, a HUGE BIG thanks to you all, especially S-Prihadi and CaliBenzDriver! Your endless support has helped me immensely, both in finding the actual problem and keeping me motivated. The repair took waaay more time than I initially expected and I really had to up my game in diagnostics skills, this car is magnitudes more complex than the cars I've been working on thus far. However, I enjoyed it a lot. This car has learned me a tremendous amount of new things and knowing you bunch where willing to keep giving me advised helped a lot.
I tried to keep a detailed log of the steps and findings throughout this thread and I hope this will be of future help to people working on these engines!
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
and hope it will be permanent.
