My Ml is ill.

Lei650

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Hello everyone,
I have a 2003 Ml270 cdi and it's currently ill. I've spent £950 on it since January and I feel I could cry.
The problem is that it point blank refuses to start when the weather is cold. I've been to 3 different mechanics. The first saying it was the high pressure fuel pump, so I had that replaced. The problem persisted. I took it back. He then said it was the low pressure fuel pipes. So those were replaced and it worked, until it got cold again. So I took it elsewhere. They had to come and get it and started it with easy start. They had it for a week and replaced the injector return pipes. I collected it and it worked. Great! Not great, this Saturday again it wouldn't start. I didn't want to call the garage that used easy start, I know over use is not good for your engine and I felt that they weren't actually finding the fault if using it. So on to the 3rd, he came to me and said the fuel pressure is low and added a pipe to my fuel filter with a balloon thing to squish to prime the engine. It's started. But now he's told me I have to pop my bonnet and prime my engine each time I want to drive it. I rely on my car, who doesn't? I can't do this prime thing each time to drive, I can't even sell it as it is. I need help people and I'm now skint. I love my car and just want it to work the way it should. Any advice would be appreciated. Thank you in advance. FB_IMG_1476977868262.jpg
 

John Laidlaw

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Presumably it’s turning over but not catching?
During all of this have any codes been read?
Yes indeed ridiculous to be doing a manual prime !
 

malcolm210

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Did the mechanic replace all the low pressure fuel lines, I think there are 3, if it starts when primed air must still be getting in between the filter and low pressure pump, this is a well known problem with circa 2000 era Mercedes might be better to let a good Independent MB garage have a look bread and butter to those people
 

mersum1es

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measure injector leak back flow...
 

Taffy7hfa

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Hi Lei650, assuming there are no warning lights etc and it runs well once started, it does sound as though your low pressure fuel pipes or O rings may be letting in air overnight, as above, it is a VERY common problem on diesel mercs of this vintage and there is loads on this forum about this problem, even though you have had some pipes replaced this is definitely where I would be looking first, try brimming the fuel tank and parking it nose down on the nearest slope overnight, gravity will sometimes keep the fuel pipes "primed" and make it more difficult for air to leak back into the system. if it is an O ring its only pennies to fix....good luck ;)
 
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Lei650

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Sorry in the reply delay all, I work evenings. I am just reading the replies now. Thank you all by the way.
 
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Lei650

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Presumably it’s turning over but not catching?
During all of this have any codes been read?
Yes indeed ridiculous to be doing a manual prime !
Hi join, yes you are right in your presumption. It turns and doesn't catch. There were 4 codes when the guy plugged in his diagnostic today but I only managed to catch 2 of them before he cleared them. I didn't catch the numbers at all. One was glow plug cylinder 2 something. Second was low fuel pressure.
 
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Lei650

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Did the mechanic replace all the low pressure fuel lines, I think there are 3, if it starts when primed air must still be getting in between the filter and low pressure pump, this is a well known problem with circa 2000 era Mercedes might be better to let a good Independent MB garage have a look bread and butter to those people
Hi Malcolm, yes all 3 low pressure fuel pipes were replaced. At the moment, as I'm sure you can understand, I don't currently have to funds to take it to a MB guy. But its certainly on my list.
 
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Lei650

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Hi join, yes you are right in your presumption. It turns and doesn't catch. There were 4 codes when the guy plugged in his diagnostic today but I only managed to catch 2 of them before he cleared them. I didn't catch the numbers at all. One was glow plug cylinder 2 something. Second was low fuel pressure.
John even. Sorry predictive!
 
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Lei650

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measure injector leak back flow...
Hi. Thank you for your advice but I have noooo idea how to do that! I am not a mechanic, I know a little but not that much.
 
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Lei650

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Hi Lei650, assuming there are no warning lights etc and it runs well once started, it does sound as though your low pressure fuel pipes or O rings may be letting in air overnight, as above, it is a VERY common problem on diesel mercs of this vintage and there is loads on this forum about this problem, even though you have had some pipes replaced this is definitely where I would be looking first, try brimming the fuel tank and parking it nose down on the nearest slope overnight, gravity will sometimes keep the fuel pipes "primed" and make it more difficult for air to leak back into the system. if it is an O ring its only pennies to fix....good luck ;)
Hi Taffy, this sounds like a plan. I have read so many posts about the same problem as mine and about O rings and maf sensors, the list of what might be wrong with my car was getting longer by the minute. I took it to people who I thought would be honest and not charge the earth, they all did and I still have the same problem. So I guess I will start with the O rings over the weekend. I'll do some research, find where they are situated and see if I can do it myself.
 

LostKiwi

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added a pipe to my fuel filter with a balloon thing to squish to prime the engine.
This is a major clue. The guy fixed the symptom but not the cause.
This 'fix' says the seals and pipes on the low pressure side are a major suspect.
Effectively what's happening is overnight the fuel is draining back to the tank and being replaced with air. The pump can't pull the air through to get rid of it so it won't start. The little balloon thing is a hand pump to draw fuel up to the pump removing the air. It's a lazy bodge.
If the seals and pipes are good the fuel cannot drain back and the car will start properly without any hand pumping.

You don't say where you're based? We can recommend places others have used that will do a proper job for next time.
 

John Laidlaw

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All of the above . O rings like any elastomer do not have a finite life so in yours they are likely to be past their best after 15 years. Hoses likewise
 

EmilysDad

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.... The little balloon thing is a hand pump to draw fuel up to the pump removing the air. It's a lazy bodge......


Kia fitted one in the factory on my Dad's Sedona ..... (an old Merc engine I believe :confused: )
 
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Lei650

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This is a major clue. The guy fixed the symptom but not the cause.
This 'fix' says the seals and pipes on the low pressure side are a major suspect.
Effectively what's happening is overnight the fuel is draining back to the tank and being replaced with air. The pump can't pull the air through to get rid of it so it won't start. The little balloon thing is a hand pump to draw fuel up to the pump removing the air. It's a lazy bodge.
If the seals and pipes are good the fuel cannot drain back and the car will start properly without any hand pumping.

You don't say where you're based? We can recommend places others have used that will do a proper job for next time.
Hello,
I am in Langley, Berkshire. Would I benefit from replacing the pipe with the hand pump to a shorter pipe? I watched him put it on yesterday so I think I could do it myself. On the upside it did start this morning without having to pump the fuel through. Took a little longer than usual on turn over but the weather is also a little warmer so I am dubious as to if it is because it is warmer or if the fuel didn't run back, bearing in mind it was stood for 11 hours.
 
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Lei650

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All of the above . O rings like any elastomer do not have a finite life so in yours they are likely to be past their best after 15 years. Hoses likewise
Elastomer? Sorry I have no clue what this is.
 
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Lei650

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**UPDATE**
Hello everyone, So after opening my bonnet to have a go at the O rings after, working out how to take the cover off the engine, thinking at first that I broke it as only half came off, I threw the cover in the boot, had a fight to get it started (I didn't use that pump thing ) by jumping it in the end (surprisingly it started, weird) I took it to SGT. They had it just short of 2 weeks.

They investigated the cold start issue, tested the glow plugs, power supply - all okay
Re-connected vacuum hoses (that wasn't me!)
Found the turbo intake pipe seal missing (my turbo had eaten it as that was fitted in January , I watched the mechanic do it)
Carried out a temporary repair to intake pipe
Carried out injector leak off test, number 2 faulty (they let me source that myself to avoid paying their price and vat)
Fitted my injector (with sealing washer supplied by SGT)
Supplied and fitted new turbo pipe seal

Along with the injector I sourced for £38 and everything above including labour I just handed over £161.47 and my car starts on the turn of the key and flies. Its doing what it should and I am so happy.

Thank you all so much for your advice, it was much appreciated.
 

alexanderfoti

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Injector leak off then! Not sure why pumping up the fuel primer helped but glad you got it sorted!
 

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