air in fuel lines

[treforj]

hi all,read with interest loads of threads and wondered what you would make of my problems.i have a c250td estate w202 1997.my problem firt started 6 weeks ago, where i had a fuel leak from a clear fuel pipe leading from the fuel lift pump,pipe replaced.ok for a week then broke down,AA said it was a faulty lift pump,new lift pump fitted along with all the clear pipe & all seals were greased,both main & pre fuel filters fitted,still air in pipes,yesturday replaced fuel filter head & heat exchanger & an inline non return valve,& guess what,still air in pipes,i am so dissapointed because this is the best car i have ever had next to my previous 190e,I would be very grateful if anybody has any ideas.
regards,treforj,

 

[230K]

Hi

hAVE U TRIED THE "O" RING ON THE SHUT OFF solenoid?

230K

 

[treforj]

hi 230K
thanks for that,will order one from dealer in the morning
regards treforj

 

[racall]

Hi

hAVE U TRIED THE "O" RING ON THE SHUT OFF solenoid?

230K

This was my problem a few months ago

 

[230K]

Hi

Is she still going bad, i have a pocket of air just before the pre filter that never goes away and does not cause any harm.

230K

 

[treforj]

hi
fitted o ring seal in fuel shut of valve,less air in system now,but do have pocket of air in pipe between heat exchanger & fuel filter after she has been standing for a few hours,starts ok though.
thanks all for your input.

 

[230K]

Hi

If you check the old o ring from the shut off valve and stretch it slightly you will see a nick in it then this was your problem. That pocket of air never goes away, i havbe tried to get rid but to date have failed but she runs perfect. Glad you got it sorted.

230K

 

[LeeW]

Is shut off valve easy to get at?What torx number is it?

 

[230K]

Hi

It is reasonably difficult to get at on the E300 Turbodiesel, removing the washer bottle helps. Not sure of the Torx size never got the hang of these yet.

Good Luck

230K

 

[treforj]

hi there again
car still going ok.in answer to LeeW if your car is a 250 td w202 it is easier in the long run to remove the inlet manifold to get at the fuel shut off valve,you will need a torx bit to get the manifold bolts off ,the size is t40.
and the torx bit for the bolts on the shut off valve is t30,and the whole job is quite easy
regards treforj

 

[steve kane]

I will have to check this on our C250D (non Turbo) we have developed bad starting over the past week and the fuel lines are full of Air Bubbles, when the car is running the clear plastic fuel lines on the filter are a constant stream of bubbles,,,mind you the problem went away for a week, then came back yesterday and thats when I noticed the air in the fuel lines,,
Steve.

 

[Blobcat]

injector run back tubes are common for letting air in

 

[c250 turbo diesel]

hi there again
car still going ok.in answer to LeeW if your car is a 250 td w202 it is easier in the long run to remove the inlet manifold to get at the fuel shut off valve,you will need a torx bit to get the manifold bolts off ,the size is t40.
and the torx bit for the bolts on the shut off valve is t30,and the whole job is quite easy
regards treforj

You no way have to remove the manifold ! just lift the windscreen washer bottle out, you can do the job no prob.

You say you have renewed the o ring on the shut off valve, dry the shut off valve off, then run for a while, then put your fingers underneath to see if wet with fuel, they can split, the valve body, new about £60 from merc.

 

[pcman_jh]

My C250 Diesel's air ingress was caused by the injector bleed off tubing/hose, the ones that run from each injector back to the fuel filter's return line. Although they looked visually OK, and since I'd changed every other O ring, when I went ot remove the old tubing some of them crumbled in my fingers!! It cost a couple of quid from the Merc dealer for 1.5 metres of tubing and it cured it for me.

A tip when taking off the old tubing, as it will be 'stuck' to the injector nipples, is to use a scalpel blade and cut the tubing inline with the run of the old tubing. This then allows you to peel off the old tube with long nose pliers.

Hope this helps.

 

[steve kane]

I wonder if the colder weather where the fuel is a little heavier prompts this problem to show itself? our C250D (W202) developed bad starting which then went away after a week and we thought it was poor quality fuel, but now its back again and looking at the fuel lines there is a constant stream of air bubbles coursing through the lines with the engine running, I'm guessing this is our problem?
Yesterday I changed the fuel filter as this was easy for me to buy and get at, but I then had one hell of a job getting it to fire up afterwards, normally once the car has been started its then just fine for the day, but I think that the lift pump was not filling the system, and it took a lot of cranking to fire up despite being warm. I have been onto the Merc dealer and have ordered up a set of Rubber Seals for the Fuel Pipes and also the one for the Fuel Cut Off solenoid, however thinking about the problem I wonder if the likely culprit is going to be on the "suction" side of the pump/system, where a leak will allow air to be sucked in rather than heavy diesel, whilst on the delivery side I would have thought a leaky seal would result in a fuel leak?? Are there any seals on the Lift Pump I wonder??
Steve.

 

[steve kane]

Well I'm just in the middle of replacing my Fuel Line O ring seals and I have to say that its not been what I would term an easy job, first its worth looking on this site for the link to an exploded diagram of the fuel lines and then have a count up of how many O rings there are, Merc Dealers seem to just show a part of the system and in my case supplied me with just 5 seals, (2 Small, 2 Large and the single larger one that I think sits behind the Fuel Cut Off Valve) of course once I started I found that there are considerably more than this, perhaps 8 or so small ones and I think just 1 Large. However the big problem I had was not being familiar with the Fuel Line Connecters & Clips and how they operate, its clear that you push the horseshoe clip through and that this then expands the clip so that the connector can be pulled out, the problem was that my fuel lines would not pull out, they were well and truly stuck in, I was not sure if the clips had released as the connectors were able to rotate quite easily but would not pull out, in the end I realised that it was necessary to just tug away and on some get a small screwdriver under the shoulder of the clip to ease it free, the trick seems to be, "Be Confident that the connector is free once the horseshoe clip has been pushed in" and just get on with pulling the little buggers out, I'm just waiting for the rest of the O rings to arrive, lets hope that this cures the problem, Good luck everyone.
Steve.

 

[steve kane]

Fuel Line Seals Update,
Number of O Ring Seals, on my c250 D there are the following,
7 Small Seals,
3 of the Larger Seals
and the 1 very Large one that sits behind the Fuel Cut Off Valve,
I hope this helps,
Steve.

 

[steve kane]

EDC Dash Light??

Well, so far I have replaced all the Fuel Line O Rings and the one behind the Fuel Shut Off Valve but with the exception of two on the filter housing(our dealer has to order more in) but there is still a constant flow of air bubbles through the fuel lines. I had previously replaced the Bleed Off Hoses just a few months ago and these still appear okay, so I'm hoping that the problem will be with one of the two remaining seals which I pulled out to check the size of and had to refit without changing, but I have to say that I don't feel too confident!!
I noticed that the Fuel Lift Pump seems to take a very long time to fill the system after anything has been disturbed, but when I had it off I checked that it would hold a vacuum against my finger which it did, I also noticed what I first thought was a small split in the alloy casting, but which I then felt was a casting mark, and like I said it does not seem to leak fuel or loose its vacuum so I'm hoping that's okay? I will of course replace the 2 remaining seals on Thursday, along with the Copper(?)washer which ought to be under the Fuel Filter Bolt but is missing and the large O Ring that I believe sits under the Fuel Prefilter. The Car is still running okay but we now have a light on the Dash, says EDC which the handbook says is a Fuel Injection Fault, any ideas anyone??
Steve.

 

[230K]

Hi

Main culprit seals that go tend to be the fuel prefilter and the o ring on the stop solenoid.
Fuel prefilter one is usually the one on the end of the pipe trhat goes into the top of the prefilter.

230K

 

[steve kane]

We now have Fierce Gear Changes!!

Many thanks for the input, I have already replaced all the seals on the Fuel Cut Off Solenoid inc the large one that sits between it and the fuel injector pump, and the seal on the "plug in" fuel line into the top of the fuel pre filter, however I noticed on the exploded diagram I found through this site that there is another larger seal on the fuel pre filter and I have this one on order, as well as the washer for the Main Fuel Filter centre fixing bolt (I don't seem to have one!) and the pair of remaining O-Rings on the fuel lines which I disturbed but did not replace, so we will see,,,yesterday we drove over to Salisbury and the EDC light came on, I assume its Air in the system that's triggering it(?) however on the return journey it stayed off, but what we have noticed is that since changing the fuel line seals we now have very fierce gear changes!! I cannot see how the two are connected but its a strange coincidence, any ideas anyone?
Steve.