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My 2012 ML350BT currently has 96k miles on the clock. It's showing a consistent pattern of a slightly long crank time when I start it in the morning after parked overnight. Cranking time is usually about 3-5 seconds and once it fires it runs fine. Usually at around 2-3 seconds it might start to fire but sounds like hard to start. It doesn't have such issue when I start it warm or parked for only a few hours, only after overnight parking. It's not temperature related either. It has had this pattern since half a year ago and even if it's ~70-80F outside it does the same thing as long as I park it overnight. Battery is almost new. My 2015 GL350BT doesn't have such issue and fires up almost immediately after the cranking starts. No trouble code is found with my cloned Xentry. Is it worth some investigation or sounds normal?
Had you done leak down test or pulled HP fuel lines in the past?
Any smell or sight of fuel on injectors, lines, or behind HP pump?
Categorically, I can only think of 2 things offhand - air intrusion into HP fuel system, is first.
Flaky CKP or CMP sensor would be the second, perhaps in the wires near where they go into sensors.
I've had to adjust my expectations since owning an R320. It just starts later than I'm used to.
My prior car was a pump deuse TDI. It started by the 2nd or 3rd revolution, once I fixed a botched recall (CKP wiring).
And it had 365K miles on it...
I noticed in the specs for the OM642, that the mechanical compression ratio was lower than the tdi motors.
The way it cranks reminds me very much of 60 Series Detroit motors, which really had to spin some before they started.
(They were 16:1 but boosted to 40+ psi)
Mine car currently has 165K miles on it, I don't know how immediately it started when new.
I went through the battery and alternator replacement last year, and it's been more or less the same starting throughout, except when it was a no-start, heh.
Had you done leak down test or pulled HP fuel lines in the past?
Any smell or sight of fuel on injectors, lines, or behind HP pump?
Categorically, I can only think of 2 things offhand - air intrusion into HP fuel system, is first.
Flaky CKP or CMP sensor would be the second, perhaps in the wires near where they go into sensors.
I've had to adjust my expectations since owning an R320. It just starts later than I'm used to.
My prior car was a pump deuse TDI. It started by the 2nd or 3rd revolution, once I fixed a botched recall (CKP wiring).
And it had 365K miles on it...
I noticed in the specs for the OM642, that the mechanical compression ratio was lower than the tdi motors.
The way it cranks reminds me very much of 60 Series Detroit motors, which really had to spin some before they started.
(They were 16:1 but boosted to 40+ psi)
Mine car currently has 165K miles on it, I don't know how immediately it started when new.
I went through the battery and alternator replacement last year, and it's been more or less the same starting throughout, except when it was a no-start, heh.
I haven't done any test or diagnosis on this matter yet just asking for opinions and I'm not even sure if it's necessary to investigate into it. There's no abnormal smell of fuel or anything around the engine at all. I didn't touch the fuel system at all during my ownership but I'm not sure if the previous owner did. I bought the car about a year ago with 85k miles on it and I drove it to 96k. I only did several routine maintenance including 2 engine oil changes, air filter, cabin air filter, fuel filter, transmission fluid/filter, differential fluid, brake fluid, front brakes, etc. I did do an A/C evacuation and recharge and replaced the valve stems due to leakage though. Also did an evaporator cleaning to eliminate the well known odor of the 166 HVAC box. I did receive the class action settlement notice for the HVAC box though lol.
It wasn't like this when I bought the car. The problem just appeared a few months ago when it was in winter. I thought it was due to cold weather but it didn't change recently when it turned warm. It feels a little strange to me although doesn't bother at all. I just want to see if it's something on its last leg or just normal wear and tear. I cleaned the MAF sensors and replaced the turbo inlet seal as well as the air filter gaskets. Also cleaned the EGR port (was about 1/4 clogged). Nothing has changed.
The most strange thing to me is that it only does this when I'm trying a cold start after parked overnight. Even if I let the vehicle cool down for like 8-9 hours (parked in my workplace parking lot) during the day it fires up immediately. I somehow suspected it had something to do with my driveway which is sloped so I parked on the street and it's still the same.
Last edited by geniushanbiao; May 27, 2020 at 09:54 PM.
i have same problem for a while now. Checked low pressure lines, high pressure lines, swapped the high pressure pump, the high pressure rail with pressure control valve. There was no change. Performed injectors leak off test, that showed me two of 6 injectors are giving two times more than the rest of them. So i am planning changing them some time. The engine works ok. When warm starts straight away. No power loss or anything.
i do not know if this is same root of the problem you have, but you could try this, when starting cold engine: turn the ignition on, wait for 30 seconds and then start the engine. This lets the fuel pump at the tank build up the fuel pressure to the engine. I am doing that when starting the car first time in the day. It does work, no delayed startup. At least some temporary solution.
..., but you could try this, when starting cold engine: turn the ignition on, wait for 30 seconds and then start the engine. This lets the fuel pump at the tank build up the fuel pressure to the engine. I am doing that when starting the car first time in the day. It does work, no delayed startup. At least some temporary solution.
^++
This morning I counted about 1-1/2 to 2 seconds cranking time.
Will try to remember to try this for myself, tomorrow morning.
When I had cranking issues in the TDI I would do it.
I have been figuring that this motor just likes a good spin before starting.
Last edited by B34chBum; May 28, 2020 at 09:18 AM.
Reason: clarity
i have same problem for a while now. Checked low pressure lines, high pressure lines, swapped the high pressure pump, the high pressure rail with pressure control valve. There was no change. Performed injectors leak off test, that showed me two of 6 injectors are giving two times more than the rest of them. So i am planning changing them some time. The engine works ok. When warm starts straight away. No power loss or anything.
i do not know if this is same root of the problem you have, but you could try this, when starting cold engine: turn the ignition on, wait for 30 seconds and then start the engine. This lets the fuel pump at the tank build up the fuel pressure to the engine. I am doing that when starting the car first time in the day. It does work, no delayed startup. At least some temporary solution.
Yes I tried the prime and it worked like a charm, no hard start just fires right up as it should. I just primed it for about 10 seconds. I guess I need to do an injectors leak down test to see if it's any of them leaking. It's just a bit weird as my car has keyless go so I can't use it the way it should work...
Is the bleeder valve on the top of the fuel filter assembly screwed down tight enough to seal? Sure sounds like you have air coming into the system when it is allowed to relax for a long time. I bet the problem would get worse if you park the car on a hill with the front higher than the back.
Is the bleeder valve on the top of the fuel filter assembly screwed down tight enough to seal? Sure sounds like you have air coming into the system when it is allowed to relax for a long time. I bet the problem would get worse if you park the car on a hill with the front higher than the back.
I didn't touch the bleeder valve during the replacement though. The filter comes as an assembly with everything already installed and I only needed to switch the mounting bracket and connect the 2 fuel hoses and electrical connector. I will take a look at the bleeder valve.
I tired ignition-On priming this morning, it made no difference - spun motor for maybe 2 seconds before starting.
I haven't done injector spill test, but given mine has +160K miles is likely I have uneven injectors.
I do have a fuel smell as well, so need to run down the leak(s).
In Xentry, go to: CDI4 > Actual Values > "Check Zero quantity calibration" and take a screen shot and post it here.
Also go to: CDI4 > Troubleshoot by symptoms > Engine knocks or clatters(i think this is the one) > "check correction over several pressure levels" and also include this screen shot.
Along with the leakoff test, these tests can uncover if there's an injector giving issues or is headed south.
I'm yet to do leak test on my injectors but correction values alone are eye opening? Correction value for calibration Units: micro seconds (µs)
250 bar 800 bar 1200 bar
Inj 1_____11_____15_______6
Inj 2_____19_____15_______2
Inj 3______8_____14_______3
Inj 4______5______7_______7
Inj 5______3______8_______1
Inj 6______8______8_______2
Looks like injector 2 is toast. Not sure what the correction limits are.
Those levels are perfectly fine. Once you approach triple digits is when its time to worry.
"Also go to: CDI4 > Troubleshoot by symptoms > Engine knocks or clatters(i think this is the one) > "check correction over several pressure levels" and also include this screen shot" - This is the more important test that will provide insight if the injector is bad before you do a leak test.
Unfortunately I don't have access to star diagnostics so I'm left with injector leak test.
For those of us that don't do the leak test along with stat instructions, how long should the car run? What are acceptable volumes of fuel injectors leak off in that test time interval?
Many thanks !
In Xentry, go to: CDI4 > Actual Values > "Check Zero quantity calibration" and take a screen shot and post it here.
Also go to: CDI4 > Troubleshoot by symptoms > Engine knocks or clatters(i think this is the one) > "check correction over several pressure levels" and also include this screen shot.
Along with the leakoff test, these tests can uncover if there's an injector giving issues or is headed south.
Sorry for the delay I have been pretty busy these days. Here are the values I have.
250bar 800bar 1200bar 1400bar
Cyl1 21.20 -4.55 6.65 0.95
Cyl2 26.55 -8.25 2.10 4.80
Cyl3 23.30 -17.65 -10.70 -5.60
Cyl4 12.20 -9.35 13.60 9.25
Cyl5 36.15 -5.15 1.85 4.75
Cyl6 27.00 -16.85 -9.95 -8.35
I guess those values look fine to me. Also it shows me that the learning cycle count for the 4 calibration points are 461 or 462. Main odometer reading is 59212km. I guess the calibration was done at this odometer reading? My current odometer reading is close to 100k miles or about 158xxxkm so not sure if it needs another calibration?
I had the same morning long crank issue with my old E270 cdi years ago. It was a failed fuel sender check vale. I put a simple check vale in the fuel hose, LHS front wheel area. Problem solved.
Looking back at my cold start issues it would appear that the main issue was the Turbo wastegate controller. I pulled mine out and sure enough 3 of the side common connectors where simply touching the circuit board. The colder it got, the worse the connection.
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