C w202 250TD - Air In Fuel system

[Mickey76]

Thanks David. That is the first diagram that I've come across that I can understand. It happened again yesterday afternoon. It is the first time it has happened during the day. It start and ran perfectly in the morning but decided to throw its hand in after standing for about 8 hours. This morning it started on the button. WHY???? If air is being drawn into the system I would think it would happen all the time. It's a bugger. If I put it into a garage it might be days before it happens again. I wonder if it could be identified on a diagnostic test. I have had them done before (No joy) but not on a Star which is difficult to find in my area. I have been told that the Snap-on system is just as good. Has anyone any experience of it.
Thanks again to all you guys out there.
John

Snap-on diagnostics are pretty good, still need someone in-the-know to decipher the codes.
Had new fuel pipes, o rings, pre filter, fuel filter- last owner (& new starter!!)
I've done delivery valve seals and new fuel pipe o rings
My clear pipe to pre filter completely empties of fuel, starting it is getting worse, can't leave it on flat or facing uphill as won't start upon return.
Will try leaving fuel cap off, wil replace filter o rings, can heat exchanger take in air?, there are no leaks visible.
Sympathies on frustration!

 

[spock500]

Snap-on diagnostics are pretty good, still need someone in-the-know to decipher the codes.
Had new fuel pipes, o rings, pre filter, fuel filter- last owner (& new starter!!)
I've done delivery valve seals and new fuel pipe o rings
My clear pipe to pre filter completely empties of fuel, starting it is getting worse, can't leave it on flat or facing uphill as won't start upon return.
Will try leaving fuel cap off, wil replace filter o rings, can heat exchanger take in air?, there are no leaks visible.
Sympathies on frustration!

Yours has a different set up tank wise which includes a strainer in the tank itself.

Have a look at the pics here, mine was the same condition.

http://www.peachparts.com/shopforum/diesel-discussion/261174-pictures-old-clog-vs-new-tank-strainer-w210.html

 

[yorkshire1]

air

quick fix if tank strainer blocked blow back down supply pipe to clear any debris off strainer, will give you a better idea, also you can bypass prefilter and or preheater to eliminate problems in this area with a length of suitable fuel hose if youve still got air looks like theres a problem with fuel hose unions letting air in. do the clear plastic fuel pipes have air bubbles in still when engine is running process of elimination really but can be very frustrating

 

[Mickey76]

Had to clean tank and strainer on last one and it was different symptoms, car would choke itself and you could see bits in cleaer pipes. Stil worth a try I guess.
No bubbles in other pipes as such and definitely none in any when running, as soon as you kill the engine, the pipe to pre filter drains completely. Didn't do this when I got the car, it's gradually getting worse. Bought pipe to do some bypassing yesterday, wish me luck!:neutral:
Thanks

 

[yorkshire1]

Had to clean tank and strainer on last one and it was different symptoms, car would choke itself and you could see bits in cleaer pipes. Stil worth a try I guess.
No bubbles in other pipes as such and definitely none in any when running, as soon as you kill the engine, the pipe to pre filter drains completely. Didn't do this when I got the car, it's gradually getting worse. Bought pipe to do some bypassing yesterday, wish me luck!:neutral:
Thanks

yes its an unusual one that because if its running without air but drains back on shut off you would expect a fuel leak somewhere when the engine is running because it would look like the air is getting in on the pressure side in that case anyway good luck and patience!!

 

[itchey]

Shut off valve

Hi guys,
I think I've found the problem. (How many times have I thought that.) The starting got worse and worse over the last couple of weeks then I found a drip of fuel oil coming from the shut off valve on the side of the injector pump and air bubbles flooding up the clear pipes. The next day it was worse and turned into a steady drip when I managed to get the engine started. Shut the engine off and air streams up the two pipes to the filter.

I phoned Mercedes and ordered the 2 end cap O rings and the bottom pipe and seals. They came this morning. Wrong parts. I don't blame the parts guy. He has been very helpful but his diagram doesn't show the end caps or seals.

In any event, the car is off the road until I can get what I need and I realy hope this is the end of the saga. If you don't hear from me again you will know that it wasn't the problem and I've put my head in the electric oven!

My thanks to everyone. You are all in my will!
John

 

[yorkshire1]

end caps

Hi guys,
I think I've found the problem. (How many times have I thought that.) The starting got worse and worse over the last couple of weeks then I found a drip of fuel oil coming from the shut off valve on the side of the injector pump and air bubbles flooding up the clear pipes. The next day it was worse and turned into a steady drip when I managed to get the engine started. Shut the engine off and air streams up the two pipes to the filter.

I phoned Mercedes and ordered the 2 end cap O rings and the bottom pipe and seals. They came this morning. Wrong parts. I don't blame the parts guy. He has been very helpful but his diagram doesn't show the end caps or seals.

In any event, the car is off the road until I can get what I need and I realy hope this is the end of the saga. If you don't hear from me again you will know that it wasn't the problem and I've put my head in the electric oven!

My thanks to everyone. You are all in my will!
John

dont know whether MB will do them as separate items it could well be complete unit,or find suitable replacements ,if you,re interested in a good 2nd hand unit ive got one inc new O ring, it was removed as part of previous fault diagnosis but it wasnt at fault

 

[CRH71]

If it's any help, mine had the same issue and the p;art number used to correct it was 6010901652 (just checked the invoice!)

Mine was leaking from where the stop solenoid joins the pump and the symptoms were similar to (although not as severe as) yours.

 

[spock500]

Hi guys,
I think I've found the problem. (How many times have I thought that.) The starting got worse and worse over the last couple of weeks then I found a drip of fuel oil coming from the shut off valve on the side of the injector pump and air bubbles flooding up the clear pipes. The next day it was worse and turned into a steady drip when I managed to get the engine started. Shut the engine off and air streams up the two pipes to the filter.

I phoned Mercedes and ordered the 2 end cap O rings and the bottom pipe and seals. They came this morning. Wrong parts. I don't blame the parts guy. He has been very helpful but his diagram doesn't show the end caps or seals.

In any event, the car is off the road until I can get what I need and I realy hope this is the end of the saga. If you don't hear from me again you will know that it wasn't the problem and I've put my head in the electric oven!

My thanks to everyone. You are all in my will!
John

The problem is John, your asking for stop solenoid seals when you should be asking for a 'Yorkshire T thingy on side tut pump'

 

[itchey]

dont know whether MB will do them as separate items it could well be complete unit,or find suitable replacements ,if you,re interested in a good 2nd hand unit ive got one inc new O ring, it was removed as part of previous fault diagnosis but it wasnt at fault

Hi. I would be interested in the 2nd hand unit. Mercedes can only supply the whole unit at £127. My email address is 'itchey44@gmail.com and my phone number is 01670 862090.
Thanks,
John

 

[itchey]

Yorky T

Ya rang David. Cumin from Northumberland it shud be caled the black pudiny thing bolted t the side o the what-d-y-cale-it that shoots watery stuff inti the big thingibybob that gans clata if aa can git the ****** stoka to hoy enough coal on the fya.
John

 

[Mickey76]

Hi guys,
I think I've found the problem. (How many times have I thought that.) The starting got worse and worse over the last couple of weeks then I found a drip of fuel oil coming from the shut off valve on the side of the injector pump and air bubbles flooding up the clear pipes. The next day it was worse and turned into a steady drip when I managed to get the engine started. Shut the engine off and air streams up the two pipes to the filter.
John

Just done o ring on shut off valve on mine today, thinking I'd cured it.... NOPE! Replaced leak off pipes too as these looked a little tired. Pipe to pre filter drains instantly, pipe from pre filter at bottom drains 10 mins later. Left fuel cap off no difference. Will do strainer in tank tomorrow (been waiting for fuel in tank to be low) and will check fuel lines under car at same time.
there is no leak that I can find.....
Any suggestions???

 

[spock500]

Just done o ring on shut off valve on mine today, thinking I'd cured it.... NOPE! Replaced leak off pipes too as these looked a little tired. Pipe to pre filter drains instantly, pipe from pre filter at bottom drains 10 mins later. Left fuel cap off no difference. Will do strainer in tank tomorrow (been waiting for fuel in tank to be low) and will check fuel lines under car at same time.
there is no leak that I can find.....
Any suggestions???

It might be helpful to others with same problem if you could take a few pics of tank/strainer (most the current help guides are for the saloon).

Hopefully being an estate it maybe a tad easier to access.

 

[Mickey76]

Would a one way none return valve at tank end stop line draining??

 

[spock500]

It would, but it shouldn't be necessary.

The design of these fuel systems evolved over many years with engines regularly exceeding 500k without replacement.

I would try and find the fault rather than cover it up with a work around. PM me if you get stuck.

 

[Mickey76]

trying to get pics on, think it will only do it as attachments.
where is strainer??? on my saloon this was on end of thicker fuel pipe (drawing fuel) on a turn out plug. no plugs on this bar the allen key drain plug. pipe goes straight into the tank.
also found (unsure how i missed) a heafty dent in fuel line (larger, drawing fuel) see pic. not pierced pipe at all, but could restrict?this wouldn't cause the problem surely?

 

[spock500]

Yup, looks totally different to the saloon - suggest starting a thread as one or two members have done this (Herbimercman) on an estate W210.

 

[paul vp uk]

Had the same problem on a discovery

Result tiny blaed screw on top of the oil filter had been overtightened causing the thread to stip,
I used a glue gun to seal it as a test
Like magic she started first turn replaced fuel filter housing
Perfect!!!
So i would think there is a tiny air leak letting air in the system

Hope this helps bud

 

[Mickey76]

thanks, have put a non return valve in at tank just temporary fix, no different, pipe to pre filter drains instantly. couple bubbles in pipe from pre filter then 10 -15 mins later completely drains as if tap was opened. is there any sealant for diesel? where is my diesel going??? if not draining back to tank?? it does seem to use more fuel when it does this but cant find leak. still looking for strainer, open new thread.

 

[turbopete]

Ya rang David. Cumin from Northumberland it shud be caled the black pudiny thing bolted t the side o the what-d-y-cale-it that shoots watery stuff inti the big thingibybob that gans clata if aa can git the ****** stoka to hoy enough coal on the fya.
John

well i understood that! which is odd considering im from Cumbria originally! perhaps relatives in Morpeth helps though!