W211 V6 CDI Cold start issue

[jon_viola]

Hi,

I have a problem with the cold starting on my 2006 W211 V6 CDI. It takes 4-5 turns of the key to get going with the resulting clouds of smoke.

The glow plugs/relay are new and functioning. The injectors have been leak tested and are ok.

The only fault codes showing are

P2644 (Not sure what this is)
&
Left Hand Hot Film Sensor out of limit.

I have swapped over the MAF's and the issue here still persists. Is this related to my cold start issue?

Thanks

Jon

 

[mersum1es]

Here is similar problem found in German forum:
280CDI W164 Fehlercode P2644 Luftmassenmesser : Mercedes ML & GL W164

Problem solved when car was diagnosed by star and fault memory cleared. And MAF should be diagnosed properly when plugged to star...

First you could check that air both filters are clean, MAF wires intact...

 

[jon_viola]

My car has just been serviced so perhaps thats caused the problem as the air filter settings not reset afterwards.

Do you think that might explain the problems with the cold start?

Thanks for your help.

 

[mersum1es]

Hard to say can faulty air mass data cause it, more often cold start problems are fuel pressure related (especially when glow plugs problems are ruled out). I would first ensure that injector leak test was done in cold conditions (too often car ha been in warm garage hours when they test it). Fuel quantity control valve, hp-pump, rail pressure regulator are next... Was glow plugs and relay changed at the same time? Faulty plugs may fry new relay unit if it was changed first.

 

[davidjpowell]

I've read about seals on the fuel lines becoming brittle and causing this. If it is that it's not an expensive fix.

 

[jaymanek]

You either arent letting the glow plug light go out before starting or you have faulty glow plugs or control units.

I have seen some interesting bodges when plugs get stuck in... Designed such that the plugs dont actually work but they stop any fault codes from coming up.

 

[SL300-24]

The symptoms seem to point to a faulty glow plug relay in my view......

 

[jon_viola]

Thanks for all your help Guys.

All 6 glow plugs were changed and then the relay in that order. I'm using Duratherms as recommended on here by quite a few.

I'll look into the fuel line seals- are these the ones going to the filter or injectors?

The leak off test was done when warmish. I'll get them checked when cold too.

The glow plug light comes on/off correctly for different amounts of time depending on the engine temp and also if you've been turning over the engine.

Once the engine's been started for the day even if left for 5/6 hours the car starts no problem at all. It's that first start of the day which is the problem.

Will do air filter reset tomorrow and let you know if that helps.

Is there a injector cleaner you'd recommend in case?

Thanks again

Jon

 

[jon_viola]

I should add that there are no other fault codes being thrown up.

Cheers

Jon

 

[jon_viola]

Ok so just reset the air filter values via star and cleared the fault code for the left hand hot film sensor. However the fault code still returns. Checked the sensor operation via star engine off and on and it's fine.

Again no other fault codes.

Any suggestions?'

 

[mersum1es]

Really weird... MAF value was middle of the green bar when tested? What star suggested to check? What are conditions/engine parameters when fault triggers?

Edit:check that all pressure sensors give rational readings and same value when engine stop (wrong pressure data may cause ecu think that MAF is giving implausible/offset value)

 

[jon_viola]

Yep all values within range. Tested with ignition off and STAR run test which from memory was held at 1500rpm.

STAR didn't suggest anything further.

Going to take it back for a longer check next week.

After the cold night last night the car was so difficult to get started this morning- nightmare!

 

[SL300-24]

I still think you have a faulty glow plug relay, I suggest that you ask one of the indy's on here but the symptoms seem to point there for me...

 

[jon_viola]

Thanks for your reply.

Even if there are no fault codes and the glow plug light goes on and off as it should? The relay is new also....

 

[BlackC55]

New from MB?

 

[jon_viola]

Yep

 

[mersum1es]

With plugged in star you'll see the fuel pressure during cold start, so fuel related problems can be ruled out if pressure stands above 200 bar in cranking. Again not warmish but cold engine!

MAF and cold start problems may not be related...

 

[jon_viola]

I'll get it checked out asap!

Thanks for your help.

 

[jon_viola]

Just a thought but would an even slightly weak battery cause my cold start symptoms?

 

[BlackC55]

Just a thought but would an even slightly weak battery cause my cold start symptoms?

Yes.

I would do a cold leak off check too.