bad starting, pump broken?

[hein]

Hi all,

I have serious problems starting my C220D (1993) from cold. The garage has changed a number of valves, seals etc., because there was clearly air in the fuel leads (big bubbles, at my first visit they just did a star diagnosis and did not even find this problem). But this did not help, and now they say the only option is to replace the fuel pump. Would this make sense?

I'm not an expert, but what I can see is that there is no longer air in the fuel leads when the engine is not running, but a constant stream of air bubbles when it's running. Is this normal, or could this be just another leak they haven't found yet...?

Thanks, Matt

 

[Blobcat]

Hi & Welcome,

There are some good technical members on here so you should get some decent advice. Have any of the o rings on the fuel lines been replaced? They crack and let air in which causes starting issues. Also any problems with the glow plugs?

 

[jibcl500]

The pre filter next to the fuel filter needs to be cleaned out or replaced as it its possibly full of crud and restricting the fuel flow, this in turn can cause air to be drawn into the fuel lines via the seals on the pipes. Always change the large O rings on the pre filter at the same time.
jib

 

[simon_wall69]

It might be worth replacing all the o rings and jubilee clips on the fuel lines first. Always start off with the cheapest alternative - and this is a reasonably easy job to do yourself.

Air in the fuel lines means that that there must be a leak somewhere.

 

[hein]

Many thanks for the replies!

Well, o-rings, fuel lines etc. have been replaced (not really cheap in the MB place here), and since then the car is clearly starting better than before, and there are no linger air bubbles in the fuel lines when cold. Electronics are fine, btw. (according to MB garage at least, but they don't seem very competent, the car was there five times now, without a proper result - I'm thinking about complaining to MB about the whole thing).

But starting is still poor, so there is a problem somewhere else. I'll tell them to check the pre filter first. As I said, they told me that they think the fuel pump replaced has to be, which is of course pretty expensive. So I only want to do this when all other possibilities have been excluded...

 

[mister_cee333]

Injectors on the 2150cc cdi engines are prone to leaking off. I've no idea if your particular model also suffers this - but it might be worth having a leak off test done. It should only cost an hour or two labour for the test. On both occasions when I've had injectors leaking off I've had steady streams of air bubbles in the fuel pipes. The cdi ones can be repaired - I was about £200 for diagnosis removal repair and refit of one injector. One of my injector problems gave me a hot start problem and the other gave me a cold start problem.

 

[piestore]

22 cdi non start

Hi
Mister is closest to the mark, once you have eliminated air in the pipes at start up ( a fair amount of air when running is acceptable) the next most likley is injector leak OFF, its a very simple quick test but is best done when the fault is present. It is very very unlikly to be the high pressure pump,

 

[Parrot of Doom]

I'd be inclined to check the glow plugs are all working correctly.

 

[simon_wall69]

You should be able to check the glow plugs circuit easily with a multimeter, I am sure there are links to doing this, if these are fine then do the leak off test, you may as well do the easiest and cheapest first.