E300 turbodiesel fuel run back

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peapod

Active Member
Joined
Jan 6, 2010
Messages
134
Location
newbury
Car
E300TD est, a180cdi
I am at my wits end with air in the fuel lines. I have replaced all 6 plastic pipes and seals, o ring behind shut off valve, injector leak off lines, fuel filter and prefilter, new clips on fuel supply and return back rubber pipes, they were loose, to the firewall. Also put a non return valve, mercedes but not original fit, before the fuel heater. The most recent fix was the shut of valve o ring and the last plastic pipe from beneath the shut off valve to the pump.

After a a 60 mile run it emptied overnight cant see any diesel have to assume the non return valve does not hold perhaps thats why there wasnt one originally but airis getting in.

If anyone gan give me new ideas they would be much appreciated. Johnsco you had a cracked shut off valve is that common?

I dont want it broken up and cant put it on the mantlepiece please please help, Olivier do you have any ideas ? Dieselman is there any diagnosic test, should I get a peugeot?

All comments very much appreciated regards peapod
 
Hi Peapod,
Did you look at your tank strainer?
If its blocked it'll create a vaccum, then the fuel will go back to the tank.
I would not recommend a NRV before the filter, it will restrain the flow to the filter/ IP.
I had similar then you, in the morning the fuel was getting back, trouble to start etc... I changed all the Orings at the pre-filter etc... Nothing was working :(
I figure out it was the assembly at the pre-filter that was badly design and always leaking air, then I just by-pass it, et voila :bannana: All good now.
I have chopped my tank strainer, and by-pass the pre-filter, I know a lot will shout " heresy", but hey, the car is running fine :p
You could try to by-pass the pre-filter. Nothing much to do, just un-plugg the clear pipe from the bottom of the pre-filter and plug it in the little heat exchanger instead of the one that goes to the pre-filter. Just bend it carefully and it should fit no bother. If it work the next day, then this is the pre-filter assembly that is your bugger :thumb:
I hope I make some sense here :crazy:
Pfff... that was a long reply :D
Olivier

PS: If you have a vaccum as the tank strainer is clogged or the tank breather is blocked, the fuel might go back via the return lins too then your NRV is useless...
 
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I had an e300 turbodiesel in yesterday with leaking delivery valve seals, causing an air in the diesel issue.

The car wouldnt start in the morning as air had got into the system overnight, draining the injector pipes and injection pump. Once air was bled from the system it would run fine all day, untill it was left overnight again.

There is a thread on here somewhere about changing these, they are not very expensive from the dealer but you do need a special socket to get to them.
 
Hi Peapod
I agree with Posts #2 and #3.
We have all had these same problems with air in the fuel lines on the E300TD.

The three most-likely points for air leaks are:

1. The fuel-filter seal.
Do not neglect this.
It is by-far the biggest seal-ring, and therefore has the greatest potential for air-leaks.
Anything other than a perfect seal and you have problems.
I have recently experienced this problem and cured it by replacing the fuel filter and refitting it very-carefully.

2. The pre-filter o-ring seal.
These are not the greatest fit.
Any dirt in the groove can easily cause an air-leak.
Again - This is quite a large area to seal.

3. The o-ring behind the shut-off valve.
These often cause air leaks.
Careful fitting of the new seal is the answer.

Yes - I had a shut-off valve with a cracked plastic body some years ago.
I have not heard of anyone else who has suffered this.

This must be curable.
All I can suggest is to go over all these points with meticulous care.
I have been impressed with the kit of VITON seals that I bought from a Forum member.
They were not expensive and appear to be holding OK.

Don't scrap the car.
Don't buy a Peugeot
:eek::eek::eek:
 
Genlemen, thank you for replies. yesterday I got a diagram of fuel lines from MB garage there is no tank breather. The fuel cap has a rubber washer and whenever I fill up there is whoosh of air into the tank. How does air get into the system to replace the burned fuel? on cars with perfect fuel systems - on fill up and on old ones it has to find a way in through seals old joints etc? Olivier I think the NRV is just not good enough to withstand the gentle tank suck back it needs pressure to work properly. Good point about restriction but it is quite big. Next time it is depressurised I will by pass the prefilter I guess it is only needed for coffee grounds tea leaves I think you are right it is uneccesary.

Olivier I replaced the strainer following your suggestion a few months back. I called into the MB garage and the merchanic said it is probably delivery valve seals as your idea Carat. But how can a seal that survives 1000psi or so leak at slight atmospheric pressure depression a little worse than cloudy. ? Anyway I took off the tank rubber seal cranked it up on two batteries left it overnight looked at it this morning - no bubbles and no sign of diesel in the pipes Oh dear.

Went off for gloom breakfast then had another look. They are new pipes and difficult to see fuel. A tiny bubble about 2mm in the delivery to the prefilter so there is fuel !

Maybe the fuel cap should have an integral breather ? mine hasn't. I will keep you posted on developments. No peugot for now thank goodness.

Neil thanks , I think this is one job which I have to sort. but thanks

You know if we couuld positively pressurise the fuel supply and return system I think most of these problems would go away.

How about a connection from the exhaust into the tank ? what do you think? yours truly. Peapod
 
I called into the MB garage and the merchanic said it is probably delivery valve seals as your idea Carat. But how can a seal that survives 1000psi or so leak at slight atmospheric pressure depression a little worse than cloudy. ?

Easy, when the car is running the fuel pressure inside the pump keeps the seals tight. Overnight with no pressure behind them, air will seep past into the pump.
 
I thought that all fuel filler caps had to have a functioning breather, atleast that was what I was told when I asked why he was checking it on the MOT ..........
 
Gentlemen HEAR THIS
Tank filter is clean.
No breather on the tank,
No breather in the engine compartment.
no breather anywhere.

Tank cap has a rubber seal. tank is always at underpressure.
It needed to breathe. I recon there was up to 7 or 8 psi below atomosheric pressure in the fuel lines after running down a full tank.

Removed rubber seal. tank breaths now >>>>>>>>>

It now fires on the first revolution no kidding - instant.
It was left for four days last week and started instantly
There is not a sign of air in the plastic lines in fact the morning after taking the rubber washer off the tank before trying to start it I could see no bubbles at all and thought the pipes were empty and my heart dropped.
In fact they were all full!!

So everybody with an E300 check your tank has a breather in the cap.

After all the pain and now it starts like a cdi no kidding no cranking.

Thanks for all the suggestions on this

At last I trust it again
 
Hi Peapod,

There is something interesting there, I'll be a wee worry to drive without a good seal tho...Once I drove without the cap on and oil went everywhere...

As I thought what you say was interesting, I took off my cap to clean it and inside there is a writing in German saying:
OHNE LÜFTUNG
Which mean:
WITHOUT VENTILATION

Then perhaps there is not suppose to be any ventilation there as the original MB cap come without...

Olivier
 
H'm, interesting thread this one, I think I'll check mine in the morning just to see, although I don't have any starting problems at the moment it's always worth having some genuine knowledge at the back of the brain box just in case
Thanks to all who offered their suggestions on this one, and of course Peabody for starting the thread

Richard
 
Pictures of my "clean" cap :)
 

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h'm, interesting thread this one, i think i'll check mine in the morning just to see, although i don't have any starting problems at the moment it's always worth having some genuine knowledge at the back of the brain box just in case
thanks to all who offered their suggestions on this one, and of course peabody for starting the thread

richard


^+1
 
With so many of us 300TD owners having such a variety of faults and remedies for the beast not starting, (my own nemesis was the delivery valve seals -see my last post here) it is a wonder that we are now not all experts on this matter. Perhaps some willing soul has time to compile "cause and resolve" and make it into a "sticky" for the benefit of those who in time will be facing the same stresses as they crank the engine over and over and over----- wishing that someone had integrated a fuel bleeding pump into the system.

Just a thought
 
vent line???

Here is a screenprint from the EPC for a 1998/9 300TD estate. The Vin came from the donor car I'm using. Not every 210 will have this application but this one deffo does cos the EPC doesn't reject the part number request.

210vent.jpg


The pic isn't hugely clear but the part numbers say 71/74/77 'Vent line'



hmmmm? :dk:


.
 
yeah they will have a little rubber breather, which you will be able to see looking up from under the car at the back of the rear wheelarch.

both my w124s have it - little rubber boot thing. Take it off (carefully as its probably gone brittle) and ensure its not gunked up at all. New ones are a few £s from Mercedes.

you could blow some air up into it to ensure it isnt blocked maybe?
 
Folks it is not over yet. :dk: Went to Stanstead left it overnight - full drainback even my fully charged battery was not enough to start it but AA did. ( I was so overjoyed last week took the spare battery and jumps out of the car). Ok once started . Will do delivery valves next week when I get hold of splined sprocket and report back. quoted by indy 2.5 hours at £60 +£5 for seals incl vat = £186 = diy. Oh dear just noticed Neil R from Star motor services offered fix it ( help == it was star that I called for the quote !) Simon from newbury MB told me you fixed his so I'm sorely tempted. I remain conviced removal of the cap washer is a help but think the non return is not up to sealing with such a low head on it, so will remove it. Olivier - so far no sign of diesel and roundabouts in this country are no good for testing it. Druk, your epc print shows a single line from to the engine, mine shows the return in parallel are your sure yours is for diesel not petrol ? Mine has no breather. This is getting like a marriage. Regards Peapod
 
Druk, your epc print shows a single line from to the engine, mine shows the return in parallel are your sure yours is for diesel not petrol ? Mine has no breather. This is getting like a marriage. Regards Peapod

I used the Vin from car WDB2100252A523--- which is a 300TD diesel I bought the engine/gearbox from for a project I'm doing. I've just rechecked on the EPC and it's from a saloon so could be different...sorry. If you dont have the EPC pm me your Vin and I'll check your specific car.

Derek.
 
Hi Peapod,
Lazy here and don't want to read the whole topic again , but,
did you look at the tank strainer?
did you by-pass the pre-filter as suggested?
see picture. 56 goes where 32 was.


Olivier
 

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