Mercedes Fuel System Diagnosis

If the engine runs normally, Based on those codes alone i would Replace fuel pump assembly, found some information related to the code 3699 but cannot post pdf here, is not an accepted file. I would also flash and SCN the engine module.

I would feel a lot better about the situation if I could find some set criteria. What could the computer be looking at considering the pressures look good but it sets the code like clockwork? I don't have a PID for pump duty cycle but that doesn't mean it doesn't exist in the computers logic. Also you would think if the duty cycle was higher to produce appropriate pressure then it would hesitate

Having the factory scanner we rarely have to get involved with such drawn out technical diagnostics. based on information i have read the normal fuel pump Idle voltage should be 5-6 Volts and current draw is 7 Amps, but this is actual values from the Mercedes scanner, not sure if yours will show this value. Does your fuel pressure bleed off or go up when static?

I do not have the voltage and amperage PIDs in the Verus OBD2 but I could check another tool that may. I just checked the pressure like you asked and it rises.

rises when off? found this in my notes from training Check engine light concern, no drivability concern. If you encounter a ME 3698 checkThe correction factor: PWM signal fuel pump via the path shown below.A 3698 will show this factor at a -15% or more--check for a restriction in the return,check return flow to tank from fuel filter pressure regulator. If there is no returnflow all available

Here's what you need to do: Start and idle the engine, go to Engine > Actual Values > Further Actual Values > Fuel System Here you can see actual and target fuel pressure, as well as "Correction Factor". 3699 will set if the correction factor exceeds 15%, a normal value is 0% to -5.0%. This problem can be caused by a bad fuel pump but it is much more commonly a vacuum leak. You also

Thank you very much for the excellent response. I am going to have to see if my other tool will give me those correction factor PIDs. I did smoke test the intake system the end of last week. I made discs to fit into the inlet ovals so I could get a good positive pressure seal. The only thing I found was the seal at the base of the two to one inlet. I would like to see if I can see that

Generally what I do is put a block off on the throttle body and go into a vacuum hose. I do love your custom block off plates though.

Mercedes has a bulletin for this where they tell you to like take a piece of sheet metal and trace the intake plumbing onto it, then run it through a band saw and glue it together!

Andy make sure you check for leaks with propane/carb cleaner, not all leaks show up under pressure. Did you check the vacuum lines for the secondary air valves and the valves themselves? If they are leaking they may only cause a vacuum leak when secondary air is active so make appropriate tests. Check the mixture adaptations you should have "idle speed range, left cylinder bank" and "idle speed

Thanks, Andrew. Unfortunately I am feeling very electronically under tooled for this. As I said the Snap-on data for this car as of 17.4 is literally worthless. I tried my Auto Enginuity to no avail as well. That had much more data, but oddly enough didn't even have fuel rail pressure, much less the correction factor that I would really like to be able to see. The only other thing we have is an

So today I installed the Y outlet/throttle inlet boot and re-smoked the intake manifold. Even wiggling the Y around it did not leak any smoke whatsoever (Although I found the MAF g/s to be extremely close to before). I then taped over the small holes under the filter housings, and around the filter inlet necks. After that I felt like the tract was as sealed as it is going to get. I then removed

Ok, so let's go with what you have and what you know. I'm not seeing anything in the fuel pump wave form to warrant replacement just yet. Did you get an rpm on those pumps? You may not have a "factory" scan tool, but you do have a damn good global OBD2 scan tool. We can fix this using obd. If you aren't intimately familiar with all the different make's correction rates and fuel strategies, then

I'm not sure how many commutators the pumps have. If it's 8 then I'm seeing about 12.5 seconds of the left pump waveform = 4800 rpm. Each segment in the screenshots is 2 ms. I have been using the global OBD2 of the Verus through the whole diagnostic. The Mercedes data on this software revision/vehicle is far too poor to do anything with. I have provided a cold start data stream, idling then

Well, hopefully that did the job. Mercedes is great about most things and I love them, but they are not great about code criteria. The actual monitor criteria are a secret that only the engineering teams have documentation on. In general, guided paths in the test tool and experience are what directs atypical engine performance diagnostics. If you have a subscription to Startekinfo even for a