R320 cdi starting problems, W251

[dotbug]

Hi all,
Yet again my poor old 2006 R320 Cdi is causing me some grief!!!

Over the past month, the car has been struggling to start in a morning. Probably taking 5-6 seconds to start resulting in cloud of white smoke.. Once the car has been started for the day, it will start fine thereafter until parked up and left over night then same thing next day...

It's almost as if it has fuel run back or similar, maybe leaky injector...???

It's now in the garage, and the lads there are going the extra mile to try and solve it but it's not looking good..

There are no fault codes or warning lights.
Glow plugs have been changed.
Engine serviced including fuel filter
Visual checks haven't thrown anything in the mix.
Fuel line pressure check resulting in one pipe been replaced due to damp joint - made no difference.
Injector leak off test not showing any conclusive evidence that it would have an injector problem...

Seems we are at a loss, and my experience with MB service isn't great, no fault codes meaning they will go through the same processes only charging .£130 an hr..

Anyone help??? Please....

 

[johnnyb]

I had the same symptoms on my cls, also without a fault code which was slightly annoying. I took a gamble on replacing the glow plug relay/control module followed by a fingers crossed test the following morning. The result was instant starting and no white smoke.

 

[leicschris]

hi

just had a very similar problem with my s320cdi which turned out to be the camshaft sensor.

cheap fix at £22 from euro car parts and 5 mins to change, after I had spent lots more money like you.

worth checking

chris

 

[dotbug]

Well guys, it's back in today 29th sept for more tests...
What I have noticed is if I preheat three times before starting then the car starts fine... I've done this randomly over the past week and every time I use more preheat it starts fine... Sounds like were onto something with the relay/control module....
I have passed info onto the garage so we'll see what happens by tomorrow ..

Cheers..

Will keep you posted..

 

[mbenz1]

+1 for glow plug relay module.

 

[dotbug]

Hello each,

For my sins I am having to revisit this issue now as its really getting on my nerves...

My local garage have more-or-less washed there hands with it and advised to leave it until the car throws an engine management light on OR doesnt start at all, so they can then trace the problem...(i am not happy with this).

The fact is though, its never got any worse, the car still has the same starting issue.... Some mornings it will start others it will do the same several seconds then start resulting in smoke etc (no falt codes/warning lights)...

Has now covered 82000 miles, running fine other than this fault..

Back in sept 2014 all glow plugs changed, relay/module changed...

I'm now thinking of going down the route of randomly changing sensors as per advice from leicschris ... will doing this throw up any lights or am i ok to just swap away OR is this a waste of time given the fault???

any one throw any further ideas in the mix??

please!?!

 

[timwood2000]

New battery?

 

[flowrider]

I had exactly the same problem except i had fault codes, replaced the glow plug control module, as others have said, and all fixed. An easy diy job for about £135

 

[BlackC55]

100% the glow plug control unit is faulty.

 

[dotbug]

Where is the module situated???

 

[bluemerc]

Where is the module situated???

dotbug, if you get a reply could you notify me, please. same car, same fualt (except no white smoke) MANY THANKS

 

[salihdeniz]

Dear Dotbug and members
This is Salih from TURKEY.
Mercedes R320CDI(W251)
Aftert the car stays a night; I try to start in the morning; the engine cranks but it does not start at the first time.
Second start; the engine starts like it's brand new.
What we tried;
- Bosch diagnosis programme ==> No fault
- Injectors leakage test ==> 2 of 6 injectors replaced and introduced
- Crank angle sensor ==> replaced
- Rail sensor ==> replaced
- High pressure fuel pump sensor ==> replaced
- battery ==> replaced
- cranking speed measured and compared with another CDI320 ==> perfect
- fuel filter ==> replaced
- no leakage observed

Our mind stoped!
All comments are highly appreciated.
Do you recommend to replace the low pressure pump in the fuel tank or to insert a check-valve on the line that is from the low pressure tank to the fuel filter?
Thanks in advance.
Salih DENİZ