E350 CDI possible fueling problem

[quinnj3]

Hi all,

I’m not sure if what I’m experiencing is common. My car is 2010 E350 CDI Coupe 227bhp. In the morning, if the car hasn’t been running for more than 12 hours, the starter motor will turn the engine over a few times before it catches on what seems like a few cylinders. It will then run off cylinder with a small amount of throttle for about 10 secs before all cylinders have caught at which point it settles down. It will then start normally the rest of the day. Outside temperature doesn’t effect this. I had it checked out a while back and my mechanic says the glow plugs are fine and no errors popping up on his computer. I returned it to the garage that sold me the car, I thought it was fixed back in the summer but the problem has reappeared. The garage changed the injectors but I have an inclination that it’s not injectors as the car runs beautifully after the initial start up. It is as though air is leaking into the fuel line while standing. Does anyone have experience of this?


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[malcolm E53 AMG]

It may be air entering the low pressure fuel lines overnight, if you can leave the car nose down overnight and see if that makes a difference, if so you’ll need to check all the low pressure lines

 

[quinnj3]

Does anyone have a fuel circuit diagram for this car? I remember when I changed the engine oil seeing a damp spot at the join of two pipes which look suspiciously like fuel lines. I didn’t have the time to investigate this at the time. I don’t recall smelling a fuel leak either though.


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[quinnj3]

Ok, today I did a leak off test on the injectors and as expected could not have been better matched. Every injector returned almost exactly the same quantity of fuel which is good as i was dreading having to fork out for injector reconditioning.

I don’t think glow plugs are faulty either as there is no fault returned by the code checker.

I’ve read that seal leaks in the low pressure fuel line as suggested in the previous posts cause the same symptoms. Is this something that affects my age of car / engine and if so what seals need replacing?


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[malcolm E53 AMG]

I’d be very tempted to run some injector cleaner through it and a few tanks of premium fuel, in my view the new generation of injectors are very sensitive to soot build-up. My 350cdi runs much better than when I bought it 2 years ago and it’s only fed BP with occasional injector treatment

 

[quinnj3]

Yes, a double dose of injector cleaner has been tried already with no improvement whatsoever. I always fill up with texaco fuel.


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[LostKiwi]

An air leak will definitely make it hard to start.

 

[andrew056]

To me it sounds like plugs and or glow plug relay , does your glow plug light come back on after the start at all ?

 

[Steve@Avantgarde]

V6 injectors have a known issue where the nozzles drip diesel when they become worn. It misfires a bit when you start it as it has to burn off the excess fuel dripped into the cylinder overnight.

It may be air entering the low pressure fuel lines overnight, if you can leave the car nose down overnight and see if that makes a difference, if so you’ll need to check all the low pressure lines

It won't be this. I understand why you posted it because of the old lumps have this issue, but they run a low pressure pump system and then have to manually crank the air through.

CDI's have an electric fuel pump under constant 4.2bar supply from ignition position 2. If it had a fuel leak (air getting in) the constant supply pressure would show a leak from a line, joint or otherwise..

 

[quinnj3]

V6 injectors have a known issue where the nozzles drip diesel when they become worn. It misfires a bit when you start it as it has to burn off the excess fuel dripped into the cylinder overnight.

CDI's have an electric fuel pump under constant 4.2bar supply from ignition position 2. If it had a fuel leak (air getting in) the constant supply pressure would show a leak from a line, joint or otherwise..

Thanks for this. What you say makes sense actually as sometimes just after starting there is a strong burnt diesel smell almost as though the car was running rich.

Hmm, this could be an expensive fix! What’s the usual fix? Full replacement of injectors or can they be refurbished?

Am I doing the car any harm by continuing to use it as is? Just until I can arrange a loan car which might be a few weeks.

Thanks

Jonny


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[umblecumbuz]

Putting the info from these two posts together suggests a possible cause:

CDI's have an electric fuel pump under constant 4.2bar supply from ignition position 2. If it had a fuel leak (air getting in) the constant supply pressure would show a leak from a line, joint or otherwise..

I remember when I changed the engine oil seeing a damp spot at the join of two pipes which look suspiciously like fuel lines.

 

[quinnj3]

I have checked this. The fluid is oil not fuel and is being blown onto the pipes from another very small oil leak.


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[quinnj3]

Well my mechanic sent the injectors away for testing. All 6 came back with a clean bill of health, no issues there. Although it means I won’t have a bill of £600+ I’m no further forward. Mechanic is going to concentrate on it now until he finds the problem.


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[Uncle Benz]

Have you checked the glow system rather than just relying on no fault codes?
Glow control modules are known for trouble on these, and are a b*stard to start if it's not working

 

[quinnj3]

I’ve had two mechanics tell me it’s not the glow system but it does appear a likely culprit as the problem is less pronounced in the summer months.


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[quinnj3]

Mechanic has checked the fuel system and doesn’t believe there is a fault with it so now checking the glow system this week instead of relying on the onboard computer.


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[ajlsl600]

is there not a non return valve in the fuel line ,when these leak back to the tank ,or filter overnight the motors can be between lazy and a bitch to start in the mornings .

 

[Westheath]

NRV is in the pump its self usually

 

[quinnj3]

is there not a non return valve in the fuel line ,when these leak back to the tank ,or filter overnight the motors can be between lazy and a bitch to start in the mornings .

Yes, mechanic jacked rear of car as high as he could to stop this happening and left it overnight. It didn’t make a difference to it starting which is why he is now looking at the glow system.


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[Westheath]

It wont make a difference as the electric fuel pump will prime the system as already mentioned.