Fuel pump (HP) renewal C270 w203 (borked and leaking)

[th3h1ghlander]

Morning all, tried starting the old gal during the cold snap on Wednesday night, she would turn over but not start. Tried about 10 times until I could hear the starter motor labour with less battery power. Called out RAC home start and while the chap was checking battery (suspecting glow plugs or battery) I smelled diesel, so I mentioned it to the chap, he agreed and checked the fuel lines and we could see that the aux serpentine belt was wet with diesel, at which point he diagnosed it as a leaking pump and the pressure drop and air ingress being the cause of my issues.

After he left (00:30am) I had a read and see that this is a common issue with cars this age and model. Replacement of the pump doesn't look hard, in fact, rebuild and seal replacement doesn't look impossible either.

This weekend I am going to take it out of the car and see if I can see if the seals are worn or the surfaces are corroded. Any tips? Thanks! Si


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[Martyn_n]

I'll be interested to see how you get on; my ML has signs of the HP pump weeping so if it's not too hard to do the seals I'll also be giving it a go.

 

[th3h1ghlander]

I'll update. Calling around for parts and prices today. I read this and it looks doable (famous last words):
http://forums.mercedesclub.org.uk/showthread.php?t=105316


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[th3h1ghlander]

Hopefully it is just the O rings on mine but I am being hopeful. See the following:

Mercedes Colindale:

Seal Kit: £36.70 0000780780

Pipes: £29.40 (CR 6120703332) + £20.32 (CR 6120703132) + (HP->LP £32.40 6120703232)

HP Fuel Pump: Exchange Unit £270+VAT Ex Delivery (6120700001 80)

O:Rings for pipes: £1.20

02082005151



Midnight Motors (Lloyds Motor Spares):

HP Fuel Pump: £145 (on order) Bosch re manufactured



Refurb Instructions:

http://forums.mercedesclub.org.uk/sh...d.php?t=105316



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[osbournedwight]

Hi as anyone know what is the problem with my ml 270 cdi 02 diesel don't want to start up in the morning i put feul pump it still has the same problem i have to put my foot and the gas pedal to get it start in the morning my name is dwight

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[th3h1ghlander]

Hi as anyone know what is the problem with my ml 270 cdi 02 diesel don't want to start up in the morning i put feul pump it still has the same problem i have to put my foot and the gas pedal to get it start in the morning my name is dwight

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I am not skilled enough to advise, probably worth posting a new topic Dwight. Do I understand correctly, you have already replaced the fuel pump? Can you see fuel in the fuel lines supplying the pump?
Lots of possible issues from my mind.


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[osbournedwight]

Yes fuel is in the lines but i don't know what is the problem i take it to 3 shops and them can't find what is the problem

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[th3h1ghlander]

Were any of these official Merc dealers? Or Indie dealers with proper diagnostic tools?

They should have been able to hook up to the relevant ECUs with Star diagnostics and checked for issues. From the other side I would have expected them to rest output pressure of the fuel pump(s) and check for injector blockage. Failing that checking the flow plugs. Start a thread on the forum and see what people say.
Does it only not start on a cold morning, are you saying that later in the day it does start?


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[th3h1ghlander]

Yes fuel is in the lines but i don't know what is the problem i take it to 3 shops and them can't find what is the problem

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See my last post, I forgot to copy you in on it


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[osbournedwight]

It wood start up in the day time but not in the morning

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[th3h1ghlander]

So, I have just finished, took off the vac pump, removed the line clamp, took the lines out of the pump and the o ring seals were obviously flattened and were noticeably thinner than the new ones. Replaced with new seals, put it all back together and it is running without any drips. Now I need to wait for a cold/freezing day and see if it still has trouble starting and leaks.


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[th3h1ghlander]

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[zipdip]

Looks like the jobs good,if people have a suspect pump then a cold snap can catch it out,especially if it gets to minus figures,there is a certain amount of wax in diesel,and so in cold weather it gets harder to pump,the refinery is supposed to put additives in during the winter but they leave it until it gets very cold,generally too late for old diesel pumps to function.

 

[th3h1ghlander]

Looks like the jobs good,if people have a suspect pump then a cold snap can catch it out,especially if it gets to minus figures,there is a certain amount of wax in diesel,and so in cold weather it gets harder to pump,the refinery is supposed to put additives in during the winter but they leave it until it gets very cold,generally too late for old diesel pumps to function.

So, yet again, predictably, temperature dropped this morning to 3deg so I thought it would be a good time to check if replacing the pipe seals did the trick...and it didn't. Fuel pissing out again. 2mins of hot hairdryer, turned the car on again, and no leak! Nothing. So, tomorrow with a day off of work is going to be a pump rebuild day. Replace all the ring seals and then hoping to be done with the issues


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[th3h1ghlander]

So, yet again, predictably, temperature dropped this morning to 3deg so I thought it would be a good time to check if replacing the pipe seals did the trick...and it didn't. Fuel pissing out again. 2mins of hot hairdryer, turned the car on again, and no leak! Nothing. So, tomorrow with a day off of work is going to be a pump rebuild day. Replace all the ring seals and then hoping to be done with the issues


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So, job done and car back on the road and no leaks! Now I just have to wait for another cold snap to see if all is good.
I took the pump off, needed a bench vice and an impact hammer driver to undo the T40 torx bolts. The rest of the dismantling was relatively easy, removed the seals and then spent some time with 400grit sand paper to remove the corrosion on the surfaces. One of the small seals was visibly damaged so hopefully that was the cause all along!

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[a111r]

The worst part of this job I found was being sure the tiny metal rings are the right way up.
My eyesight's just not up to small scale stuff.

 

[th3h1ghlander]

The worst part of this job I found was being sure the tiny metal rings are the right way up.
My eyesight's just not up to small scale stuff.

They were fiddly. I am fairly sure I got them the right way around however they would not stay in when the head was upside down so had to keep pressure on with the piston mount.

The worst part of the job by far was getting the bolt back in under the pump to attach to engine


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[th3h1ghlander]

I'll be interested to see how you get on; my ML has signs of the HP pump weeping so if it's not too hard to do the seals I'll also be giving it a go.

All done, and it wasn't too hard at all (if you have the right tools)


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[a111r]

They were fiddly. I am fairly sure I got them the right way around however they would not stay in when the head was upside down so had to keep pressure on with the piston mount.

The worst part of the job by far was getting the bolt back in under the pump to attach to engine


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The mounting bolts were easy on my OM613 engine.

I don't know if I did it right...as the pump's still on the shelf as a spare.

 

[th3h1ghlander]

The mounting bolts were easy on my OM613 engine.

I don't know if I did it right...as the pump's still on the shelf as a spare.

May be slightly different for you but as the two fuel pipes are stiff and obstruct the bolt access while there not being a great amount of space between the fan and pump for tool access:

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