'99 C250 TD W202 with air in fuel line - won't start

[guydewdney]

You might have a blocked inlet pipe in the tank. I blew mine out with an airline, cap open, half a tank of fuel, blow gun in hose at engine end, blow until you get a clear bubbling noise. Cant hurt.

 

[Olivier]

Could be that too.
This is my tank strainer. The merc died 3 times on the highway...
My way back home has only been possible by switching the fuel pipes and running on the return...
Scary picture...

 

[neilrr]

C250 TDs don't have tank strainers.

 

[skattrd]

Hi all, I'm having an issue with air in the fuel line as well, 1998 w202 c250TD. I've replaced a few pipes and o rings, but it's still got air in it. Can anyone suggest where the air might be getting in to the system?
In the diagram below pipes numbered 83, 56, 74 can be seen to have air in them, the others have none.



Any suggestions as to where the air might be getting in?

Thx
Chris

 

[toolman1954]

Hi,
Due to the poor design the air can get in the system in several places and there are many threads on here for you to read about the trials and tribulations of getting rid of the air. But really you need, in my opinion, to start from scratch. It is of no use replacing the odd O ring here and there, on a vehicle of your age the pipes will now be old and hardened, so a good start is to replace all the plastic pipes with new ones from the dealers, they are not are fortune. Before you start making a mess with diesel, put your hand on the fuel pump and check that the delivery valve seals are dry. A 1998 vehicle is of the age where these 5 seals can leak and just one letting in air can cause much misery. If these are leaking then you need to decide on a DIY approach as many have ( I tried and failed )or get a Diesel Specialist to sort it out for you. Do not forget you will need a good battery when bleeding the air out. Good luck Regards Steve.

 

[skattrd]

Thx for the reply Toolman. I have a ful set of o rings I bought off ebay and a some plastic pipes on order from the local MB garage. I fitted the pipes they had in stock today the rest I will do next week.
I was hoping that someone may be able to point me in the direction of where to look though as only 3 of the plastic pipes have air visible in them.

If there was a diagram somewhere of which way the fuel runs through the system I should be able to work out where the air is getting in myself.

 

[skattrd]

Is this diagram (found elsewhere on this forum) correct?

If so then it would appear that 56 is where is air is getting in to my system as the other pipes that show air in the line are after this in the flow of fuel.

 

[Fearris]

Hi guys. I experience also the issue with air in fuel lines. My car 1998 c 250 TD , estate (combi) 1998, manual 5 speed gearbox.
So lets start from beginning. Mine shut off valve was leaking fuel.
After i got the car to my mechanic(specialized in MB , indy garage) he removed it and found out that previous owner
must have tried to reseal it with SILICONE !! instead of new o-ring. So he cleaned
the location and replaced the o-ring between shut off valve and fuel pump. He also replaced
one of the o-rings inside the shut off valve as it was leaking a bit as well on the
side of it(this was non original o-ring). He also replaced all the return fuel lines that
connect the injectors,cleaned the pre-filter next to the fuel filter.After that he replaced all the o-rings on fuel lines with original
MB parts.After putting it all back together no fuel leak,but the check engine light came on as well
as the issue with the engine going off couple of seconds later after i turned the key off(never happened before).
Mechanic erased all the fault codes in ECU (plenty of them because i had many parts replaced).
After that the check engine light disappeared once only to reappear before me driving home. He explained to me
that usually after the fuel system bleeds itself of air the engine light should go off.
I drove the car gently so i noticed only at the highway that the car drove itself as non turbo(maybe limp mode?).
This was however already late so i drove it home . I did approximately 100+miles and the car started losing power (maybe 10 miles to go)
as if low on fuel, losing rpm and eventually it died on me twice before i got to the apartment driving it in higher rpm 2500+.
I ordered and replaced the shut off valve with new one(done by my friend-clean job). The check engine light still comes on.
After priming the fuel with primer bulb and turning the engine over, it started. However it was running unevenly , there was lot of
air in fuel lines(and the check engine light). After while it calmed down but still air in fuel lines .Now - the line no.83 was full of foam like mixture of
fuel and air with engine running (car parked with drivers side on curb,eu-car and less than 1/2 of tank full).Next day it started but still took some priming
and couple of tries before it fired up. I drove it up and down the street gently for a bit and after i decided to do a bigger round around the
block I put it in the 3rd gear(manual). The engine chocked and died as if low on fuel again.
After 3 tries it started again , I drove it back to the apartment and let it run, held rpms around 2500 for a couple of minutes and idle it again.
It seemed better but air still in lines. So i tried do fill it up, refuelled to approx. 3/4 of tank next day.After that i primed it couple of times
and on second try it started but still unevenly(air in fuel lines). However I noticed this the fuel-air foam in fuel line 83 has improved with less air in(the car
now parked with passenger side on curb).
Also after letting it run and holding the rpms higher again i shut it off(again died every time couple of seconds after turning the key off-infra key is new).
Almost immediately there was air in line no.56. I could also see the air bubbles slowly coming from shut off valve via fuel line no.95 into the fuel filter.
Anyone with similar issues or any ideas how could this be fixed?
All ideas are welcome.

 

[jaaa1976]

Hi guys. I experience also the issue with air in fuel lines. My car 1998 c 250 TD , estate (combi) 1998, manual 5 speed gearbox.
So lets start from beginning. Mine shut off valve was leaking fuel.
After i got the car to my mechanic(specialized in MB , indy garage) he removed it and found out that previous owner
must have tried to reseal it with SILICONE !! instead of new o-ring. So he cleaned
the location and replaced the o-ring between shut off valve and fuel pump. He also replaced
one of the o-rings inside the shut off valve as it was leaking a bit as well on the
side of it(this was non original o-ring). He also replaced all the return fuel lines that
connect the injectors,cleaned the pre-filter next to the fuel filter.After that he replaced all the o-rings on fuel lines with original
MB parts.After putting it all back together no fuel leak,but the check engine light came on as well
as the issue with the engine going off couple of seconds later after i turned the key off(never happened before).
Mechanic erased all the fault codes in ECU (plenty of them because i had many parts replaced).
After that the check engine light disappeared once only to reappear before me driving home. He explained to me
that usually after the fuel system bleeds itself of air the engine light should go off.
I drove the car gently so i noticed only at the highway that the car drove itself as non turbo(maybe limp mode?).
This was however already late so i drove it home . I did approximately 100+miles and the car started losing power (maybe 10 miles to go)
as if low on fuel, losing rpm and eventually it died on me twice before i got to the apartment driving it in higher rpm 2500+.
I ordered and replaced the shut off valve with new one(done by my friend-clean job). The check engine light still comes on.
After priming the fuel with primer bulb and turning the engine over, it started. However it was running unevenly , there was lot of
air in fuel lines(and the check engine light). After while it calmed down but still air in fuel lines .Now - the line no.83 was full of foam like mixture of
fuel and air with engine running (car parked with drivers side on curb,eu-car and less than 1/2 of tank full).Next day it started but still took some priming
and couple of tries before it fired up. I drove it up and down the street gently for a bit and after i decided to do a bigger round around the
block I put it in the 3rd gear(manual). The engine chocked and died as if low on fuel again.
After 3 tries it started again , I drove it back to the apartment and let it run, held rpms around 2500 for a couple of minutes and idle it again.
It seemed better but air still in lines. So i tried do fill it up, refuelled to approx. 3/4 of tank next day.After that i primed it couple of times
and on second try it started but still unevenly(air in fuel lines). However I noticed this the fuel-air foam in fuel line 83 has improved with less air in(the car
now parked with passenger side on curb).
Also after letting it run and holding the rpms higher again i shut it off(again died every time couple of seconds after turning the key off-infra key is new).
Almost immediately there was air in line no.56. I could also see the air bubbles slowly coming from shut off valve via fuel line no.95 into the fuel filter.
Anyone with similar issues or any ideas how could this be fixed?
All ideas are welcome.

Hello..did you fix problem ? i have same problem ..car died on road when i have 1/4 fuel in tank.Replaced all oring and shutoff valve from spare car.still have air in lines..can be problem in tank?

 

[neilrr]

Check the fuel pre-filter, # 26 in post 44.

 

[a111r]

Hello..did you fix problem ? i have same problem ..car died on road when i have 1/4 fuel in tank.Replaced all oring and shutoff valve from spare car.still have air in lines..can be problem in tank?

Did you also replace the shut off valve's O-ring or re-use it?
I think I've still got some new ones.

 

[jaaa1976]

Check the fuel pre-filter, # 26 in post 44.

I connect pipe direct from metal pipe to shutoff valve..but still i have air bubles.

 

[jaaa1976]

Did you also replace the shut off valve's O-ring or re-use it?
I think I've still got some new ones.

hi..I reuse old..looks good..and i put ptfe tape on this oring ..but still same bubbles..i dont have this oring at the moment..if you have i can buy or which size i need ? I think problem is in tank? car not working now because is only 1/4 diesel in tank.? and is hard to pulling diesel in pump.. also i have EPC light on dash..car working without turbo..not power now..i replaced crancshaft sensor and maf sensor.. how i can reset this light ?

 

[a111r]

I'll check my stock and let you know. The only dash light I've ever had on with these was down to a failed brake light switch.
OM605s have a MAP not a MAF, IIRC?
Yes more fuel in the tank will help. I used Easi-Start rather than kill the battery dead, twice.

 

[jaaa1976]

I'll check my stock and let you know. The only dash light I've ever had on with these was down to a failed brake light switch.
OM605s have a MAP not a MAF, IIRC?
Yes more fuel in the tank will help. I used Easi-Start rather than kill the battery dead, twice.

I bought this oring today ORings 12mm ID x 3mm CS 18mm but problem is i think in tank..i have spare tank from mercedes i buy for spares..I will replace sender unit

If dirty fuel is added to the fuel tank, it is likely that some of the dirt will cause a blockage of one of the venturi pumps.
- If the passenger side venturi pump gets blocked, the tank sender for that side can be removed and either have the venturi pump cleaned or the whole assembly replaced.
- If the drivers side venturi pump gets blocked, due to its location at the back of the fuel tank, it is impossible to remove it for cleaning or replacement.

 

[a111r]

If dirty fuel is added to the fuel tank, it is likely that some of the dirt will cause a blockage of one of the venturi pumps.
- If the passenger side venturi pump gets blocked, the tank sender for that side can be removed and either have the venturi pump cleaned or the whole assembly replaced.
- If the drivers side venturi pump gets blocked, due to its location at the back of the fuel tank, it is impossible to remove it for cleaning or replacement.

The venturi is not a pump. It's about the relative diameters of pipework, that creates suction from flow.
Whoever wrote that ^^^, should be ignored. It's not a tank problem... it never is.

 

[jaaa1976]

why me car stop when fuel in tank show 1/4 ?..I think in tank is some blockage..
the fuel tank venturi leveling or transfer system in the saddle tank on c250td mines obviously not working properly because it says quarter of tank when its empty could this not working venturi get air from empty part of tank and allow it to travel up return line to filter housing and into system when car is shut off ?