Fuel supply problem - W203 220 cdi

[nujon]

Disconnected the fuel return line at the n/s sender unit and diverted to a jar via an 8mm hose with a 2mm nozzle at the end (similar to size of spray pump nozzle) - started the engine and observed the flow on a range from idle (700rpm) to 4000 rpm.
At idle to 1000 rpm, there was merely a dribble - this is clearly not enough to drive the spray pump (cannot be design intent as the car would run dry in a traffic jam!). The flow incresed with rpm but with a considerable amount of air/vapour visible in the line - I am pretty confident that the fuel supply side is airtight so where does this come from !!!

Also spoke to MB Head Mechanic at nearby town - told him I had replaced engine bay fuel pipes, rail regulator, sensor and lift pump and that no HP pump leakage - he said try the following in order:-

1. confirm no excess injector leak-off (confirmed virtually nothing at idle)
2. fit model-specific MB fuel filter and no other - said filters for pre and post facelift W203 220 diesels were different internally and that fitting wrong / aftermarket filter common cause of problem - resticts fuel supply rate!
4. replace the swirl pot in tank o/s - says this also a common cause of problem but says no-one knows exactly why - possible age-related internal distortion / internal separation of welded plastic seams

 

[cyberflex]

Nujon, ring Bosch UK automotive technical department and speak to the guys there, when I called I stated that I had a W203 C320 M112.946, the tech was able to send me a document via email attachment that had every single Bosch part number for my particular application, be that alternators(new and exchange) starter motors, plugs, filters, headlights e.t.c.

I then went to ECP, who just used the registration of my vehicle and gave me the correct Bosch fuel filter for my specific application, I then double checked this with the Bosch part number that was in the PDF that was sent to me by Bosch technical, they matched perfectly, I needed to be 100% sure after the disaster I had with the previous 2 fuel filters from a manufacturer that I would rather not name.

Also you can go to the Hengst website and get the correct Hengst part number for your application from their very efficient and accurate online catalogue, I really wanted to go for Hengst but ECP did not have any stock, so Bosch it was, really impressed, solved the cranking issue immediately, Bosch filters are now up there with Hengst in my world, also just for info. I recently emailed Hengst HQ to see if their filters were available elsewhere, they gave me the contact information for a dealer they have in Ireland.

IMHO, I do not think the Mercedes one will differ in any way quaility wise to the correct Hengst or Bosch fuel filter. They really are the best from everything I have read and experienced and also techs I have spoken to lately.

I am so glad Jay has seen issues with certain fuel filter brands on our cars, I thought I was the only one. Hengst or Bosch all the way!!

Hope you get to the bottom of this problem.

All the best.
Jon.

 

[cyberflex]

Just to add to this, I think I may know what the problem may be, I have just been on the Hengst site and there are slightly diiferent part numbers for fuel filters for the C220 CDI depending on which variant code is used 203.006 or 203.008, these give rise to 2 different engine codes also. There is one part number shared for both applications, aswell as one specific part number for 203.006 and another for 203.008, so 3 part numbers in total, very interesting. I really love Hengst, they really are number one when it comes to filters, it is all they do and more importantly do well, at the end of the day.
But please call Bosch aswell, they more than likely have a specific application aswell.

Take a look, it may well be, this could help with a solution.

I do not want to post a direct link to the various pages in case it is against rules, but please go to the Hengst homepage, access their online catalogue and search for W203 C220 CDI and you will see what I mean, also try calling Bosch aswell.

Hope for the best.
Jon.

 

[nujon]

Still on with this issue - fitted an MB fuel filter and now waiting for the tank to get to half-full to see what happens (not optimistic !)

Done a leak-off test with a Sealy kit, results:- No1= 8.7ml/min, No2=10.0ml/min, No3=11.6ml/min, No4=9.6ml/min - I don't know if these results are good, bad or indifferent - can anyone in the know comment?

Also noted that on reving the engine to 3000rpm, a stream of small air bubbles can be seen in the fuel line leaving the filter - I presume this is not normal ? - noting that I have renewed all the under-bonnet fuel pipework, the air in-leakage may be occuring:-

1. via the pre-heater
2. the rubber pipe connecting the steel fuel pipe at the rear of vehicle to the rigid black plastic pipe running to the tank
3. the short rubber pipe connecting the plastic pipe at (2) to the sender unit
4. the pipe interconnecting the sender units inside the tank
5. the swirl pot

- any views most welcome

 

[cyberflex]

Hi Nujon,
Sorry you have not got to the bottom of this yet, guys like Jay, Olly e.t.c. who know their stuff will be along to analyse your results and hopefully you will be sorted, may be you could plan a trip to one of 'our' guys on the forum (even if it means on the back of a low loader) to get to the bottom of this, once and for all??? Worth considering IMHO.

All the best.

Jon

 

[nujon]

As I feared, the MB fuel filter made no difference - nor has renewing the short rumber fuel pipes at the rear of the vehicle (chassis to polycarb pipe, polycarb pipe to n/s sender unit)

Have noticed the following however:-

With the fuel in the o/s of the tank down to ~ 5l or less, intermittant bubbles can be seen in the plastic fuel line from the filter to the lift pump @ tickover - as the rpm is raised, an increasing number of smaller bubbles can be seen streaming through this line. With the fuel tank full however, no bubbles are evident below 2500 rpm - with everything I have gone through so far, I am caused to ponder the MB mechanics suggestion as to the swirl pot (fuel tank o/s) being somehow responsible

 

[nujon]

Solved courtesy of advice from Steve @ **********e Automotive - many thanks Steve

 

[jaymanek]

what was it?

 

[142 TPL]

Share you findings with us

 

[paresh]

What was the problem? I'd like to know how you solved it as I think my W203 is starting to show the same symptoms that you experienced.

 

[142 TPL]

Don't just leave us hanging. You need to finish the story

 

[142 TPL]

Don't leave us hanging we all need to know

 

[142 TPL]

Bump

 

[142 TPL]

Looks like we will never know

 

[alexmoon]

What was the solution – we need to know!

 

[nujon]

SORRY ALL - solved on eve of goin on hols - just back and jet-lagged - will reply fully in next few days

 

[andymerc]

High pressure fuel pump?

 

[paresh]

Yeah, I think it was the High Pressure Fuel pump as well.

 

[142 TPL]

I think it will be an air leak

 

[142 TPL]

Well ??