W210 E300TD 1999 Fuel leak

[Rob H]

I have a slight fuel leak that seems to be coming from the joint between the Injector pump and the fuel solenoid (black plastic). There are two bolts that hold the solenoid on to the pump and a small 'O' ring that seals the two. I have had it apart and all looks OK but I guess it just needs the seal changing.
Is this a common leak point and is there where else that tends to leak?

Starting after re-assmbly is a bit slow but I guess this is just a symptom of the air needing to bleed out.

 

[johnsco]

I have experienced the same leak not so long ago.
It turned out to be the body of the fuel-cut-off solenoid that was leaking.
Had to change the unit.
It was not easy to see exactly where it was leaking from.
Changing the seals did not cure it.
Changing the unit did.

While you are under there, have a long hard look at all the many plastic pipes and seals under the inlet manifold.
They are also rather prone to deterioration as these cars get older.
This can give rise to minor air leaks and difficult starting.
Fortunately not that expensive.

 

[Rob H]

Thanks for your reply. I had a quick look at the fuel shut off valve when I took it off yesterday and it looked OK, but will have a closer look later (with magnifier, as eyes are not what they used to be!) Dealer has a seal in stock, so I will have another crack at it tonight.
I have also found a thread about this from some time back (Parrot of Doom) that covers the subject quite well.
Will also have a good look at the pipes.
Any tips on getting it started afterwards? or do you just keep it cranking.

 

[johnsco]

Just make sure that you fill the filter and pre-filter.
You probably won't need to disturb these anyway.
Then keep cranking.
It should start without too much trouble ... Although it might grunt a bit at first.
If it doesn't start easily - Do rest your starter motor between tries to prevent overheating of the windings.
They do take a lot of electric current.

 

[philiggy]

Hi
Its common for the o-ring on the solenoid to leak, take the washer bottle out and you'll get better access, not a difficult job


Phil

 

[peapod]

thanks everybody don't have the problem yet but very useful info, ps piggybacking another battery helps with the restart after fuel filter job, peapod

 

[lbj]

Fuel leak saga - who do you trust?

W210 with 124K - I had a fuel leak that started after £300 service. Things were done that needed to be done and I accepted the cost - with an MOT done at the same time. Garage said that they had not worked in the area where leak was ( fuel pump area ). So went to Mecedes and they gave it a free safety check and could not find a leak?

There was a leak though. Starting became a problem so returned it to garage. They had it 7 weeks and said £400 please and you've "got a result". That is the £400 was cheap for the work they had done - although they were not specific - some chain adjustment, injectors checked - one of them reconditioned, and more!

Two weeks after I had picked the car up - I had to go to France - it was hot so I booked in to top up the air-con system - to make sure system operated well. On lifting the bonnet - fuel was leaking from the full length of the engine - I was ushered away but returned to see that every injector pot was FULL of fuel - not good to travel 1100 mile round trip. Apparently after one hour and two attempts they fitted the correct bore injector excess fuel lines, ( whatever they called them - sorry I'm not a technician ). They said - "who'd have thought Merc's fitted micro-bore lines"! So - off to France - no problems but NO POWER! The car drove OK but no Umph! On my return I took it to Mercedees for a "Health check" and apparently: The fuel was leaking again, The MAF was NAF!, G/B was stuck in "W" mode and some other bits needed doing.

Well - I had to take it back to the original garage to "rectify" leaks - but when they openned it up - dry as a bone! I had ordered the MAF and new S/W switch from Mercedes and asked them to fit them - The original garage said that they would do ALL the work for free - including fitting MAF and switch. So I let them do it! O'h - bye the way did I mention that I could NOW see air in the clear fuel pipes near the fuel pump at start up!

Took the car out again - slight improvement in performance, ( with new MAF ), but I was told that they had not thought it needed a MAF and / or S/W switch. Mercedes had said that MAF was reading 50 and should have been reading 140...something or other - but when I told my garage this - they said that if the "EGR"? valve? was sticking / not working well the MAF would be "reading low" - so perhaps I had spent £182 for nothing, and they would sort out the "EGR"? later as they were very busy!

But SURELY Mercedes would have taken the "EGR" thingy into consideration before calling for a new MAF! Wouldn't they?

Took the car home - bit better performance - but there was a fuel leak.

This is where it all started! £400+£240 later and still a fuel leak and diminished performance, conflicting reports from two garages ( one of them mercedes ). Who do you trust and is there patron saint of mercedes to whom I can prey for "insight". I am ignorant - but reading through these pages I see that I am not alone - and that we are at the mercy of the garages. I live in hope! Thank-you for letting me share this - I feel better!

 

[johnsco]

Sorry to hear about this tale of woe.
If you look towards the bottom of the main menu. you will see a section ... Members Offers by Traders.
These traders are trusted members of this forum.
Depending on where you are in the country, one of these may be able to help.

 

[lbj]

Thanks for reply

Just calculated a rough 31 mpg - but only rough and this from a run when I'm trying to "find the power", that is test it up hills, for example, to see how it repnds. I suspect that this "testing" wastes fuel. It's driving OK - gd it's a MERC! But I think it's not working as it should - and that's what we all want - isn't it!

My problem is that I'm not up with cars nowadays - I guess I'll have to do more research - like this forum - and NOT TRUST the garages AS MUCH. They all have overheads and our cars are simply a means to profit - very few ( if any ) truly investigative / treat your car like their own mechanics left out there!

Great car though - love it to bits - it deserves to be treat with respect!

I'll be back!

 

[1965toxic]

I have experienced the same leak not so long ago.
It turned out to be the body of the fuel-cut-off solenoid that was leaking.
Had to change the unit.
It was not easy to see exactly where it was leaking from.
Changing the seals did not cure it.
Changing the unit did.

While you are under there, have a long hard look at all the many plastic pipes and seals under the inlet manifold.
They are also rather prone to deterioration as these cars get older.
This can give rise to minor air leaks and difficult starting.
Fortunately not that expensive.

Johnsco, was this job a big one i think mine has the same fault, changed all my pipes think this is the last thing now, its intermittent too which does not help....thanks in advance Tim

 

[johnsco]

Hi Tim ... It's not a difficult job to change.
Remove the washer bottle first.
It's fiddly but not difficult ... Like all those jobs under the inlet manifold.

Also - Have a look at the thread started on 25.09.09 from ali300TD.
(Last post ... 30.09.09)
[One day I'll learn how to reference a thread]
This may give one or two useful ideas.

 

[peapod]

hi Johnsco. hope you are keeping well and and E300 too, this an old thread but relevant to a problem I have. Concerned about ageing plastic pipes I replaced them, all the ones the dealer said would need replacing i think 6, I also did the leak off pipes that was last summer. After a very cold start and only a 2 mile drive then stop for thirty minutes I had fuel run back no fuel the lines. I knew the only solution to get moving was a long crank (with breaks) it worked. Afterward i remembered one non replaced leak off pipe (i did not have enough of it at the time) changed it. All was fine for two weeks but today it happened again. On my car any air leak into the system results in this problem. Can you tell me please ? is there a non return valve in the system which should prevent fuel running back to the tank ? Also please if I have a slight leak on the solenoid valve o ring you mentioned, is that a likely source of air ingress? I don't appear to have any fuel leakage down there which has always led me to believe it is ok ? Any tips much appreciated. Regards Peapod

 

[Olivier]

You might have a blocked tank strainer, this will suck the fuel back into the tank.
Also the prefilter is always leaking on those car as the connections are not build properlly and are too many. This is why there is always a bubble on the pipe going to the prefilter.
I think that if the shut off valve leak air the fuel might draw back to the tank as well. Get the Oring and see?
Check the tank strainer, you might get a surprise...

 

[peapod]

olivier, thanks for quick post I have ordered the o ring. I am pretty sure it is the o-ring as my car is always parked downhill and the problem has only occured parking on the flat. Tank fuel level looks to be almost the same as the height of the o-ring when facing downhill ! I saw the downhill idea in another post. Regarding tank strainer, does the tank have to come off to do the strainer ? I will look at that also. thanks and regards peapod

 

[Olivier]

I don't know about the estate but I think its a lot easier then the Saloon for the strainer and its just go undder and "unscrew it"
But defo have a look at it. My latest was totally clogged and no fuel was going through ( only after 1000 miles), as a result I had to get the car tow away to a place where I could do the strainer...

 

[SilverSaloon]

see here:

http://www.mbclub.co.uk/forums/engi...el-tank-strainer-w124-w210-estate-diesel.html

 

[johnsco]

Hi Peapod.
Sorry for slow response.
Hadn't noticed this post.
The O ring seal at the back of the diesel shut-off valve is a common diesel leak.
I've got a leak there now and it needs sorting.
However ... Haven't noticed any problems starting.

Olivier's comments about the tank strainer are worth taking on board.
I agree that the O ring seal for the pre-filter can be troublesome.
Make sure that the seating of the O ring is perfectly clean and that it is correctly seated.
It should seal OK.

 

[peapod]

hi Johnsco thanks for helpful comments.
for info I read a thread that mentioned a non return valve merc part no MA 0004763732 which was a solution to fuel run back and enquired of the dealer. It was never fitted to W210 and was standard on W124 diesels. Dealer said on the phone it goes into the " tank return line" (on 124's) , I have ordered it . However I am in a bit of a dilema how can a non return valve work on a return line ? surely if fitted in the line in the direction of flow it will do nothing. fit it the other way round and it will stop the return line working ! a mystery at the moment. Maybe it is a sort of automatic air bleed but surely that will not work as the return line is under suction / negative pressure. Do you have any ideas on this ? The valve will arrive later this week ( £39 ) maybe an expensive mystery. I have the shut off valve o ring so plan to do both jobs at the same time. Regards Peapod

 

[Olivier]

Is that the banjo bolt at the back of thre IP?
If yes I really doubt it is your problem at all.

 

[johnsco]

All the O rings in this area get "tired" as the cars get older.
The one that seems to come up regularly is the O ring at the back of the diesel shut-off valve.