non starting C250 TD Estate

[fwd]

Hi... would appreciate a bit of advice...

Would a failing lift pump (bolted to the side of the inline injector pump) cause masses of air to be present in the system as seen in ALL the plastic lines ?

I have changed all the o rings on the pipes, pre-filter and shut-off solenoid, even bypassed the fuel tank with a make-do gravity feed and return, elliminated/bypassed the fuel heater to no avail

Any idea how much these pumps cost and is it a MB item or can it be bought from elsewhere ?

Thanks in anticipation...

 

[Dieselman]

Hi and welcome.
The lift pump wont cause air at all the pipes as it is after the pre-filter.

The sequence is from the tank, through the fuel heater on the cylinder head, pre-filter, lift pump, main filter, stop solenoid, inection pump.

You have air leaking in early on wherever you see the air first is where it's leaking.

It could be the pipes, pre-filter or fuel heater leaking.

 

[BlackC55]

The fuel filter housing has been know to be porus.

 

[fwd]

Thanks Dieselman / BlackC55 ... I have eliminated the heater by by-passing it, the pipes were replaced in February and resealed a few days ago.

The odd time I managed to get it started the FEED PUMP TO FUEL FILTER line became literally full of 'foam' and all the other pipes had air in them.

If the lift pump was faulty, would the engine 'ever' start ?

Porous filter housing... that will be a pig to suss out bar substitution!!!

 

[Dieselman]

Which is the first pipe to show air bubbles?

To suss any part of the system just bypass it.

If the lift pump is faulty it will start as long as fuel is being fed to the injection pump gallery without too much air.
At idle about 80% of the fed fuel is returning to the tank anyway.

 

[fwd]

The problem is that at present I cannot get the air out of the system!!! so it is difficult to located the first 'offending' pipe.

Even when I gravity fed the filter bowl and let the fuel syphon thru' to the return line into a ground level container, air appeared in all the pipes whilst cranking ! even then it would not start.

Since March, it had let me down on 2 occasions where I almost flattened a newish battery before it started - but this time 'nada'....

 

[Dieselman]

The system is self bleeding so wherever you see air first is where it is leaking in.
Is there air in the pipe leading upto the pre-filter front the fuel heater?

Have you tried running the car from a can connected to the lift pump, you may have air leaking into the main black feed pipe.

 

[Glenn Smith]

Believe it or not but a blockage can cause foaming in the pipes also, so you may not have an air leak, try pressurising the system with a little compressed air to find a leak.

 

[fwd]

:bannana:

Thanks you all, sp Dieselman - while it was in kit form, decided to replace the fuel filter just to find the seal split, basically held together by the tightness of the bowl against the housing, surprising enough, there was no fluid leak!

So my starter motor is saved, my hair is beginning to grow again and my sanity is restored

Thank you again

 

[Dieselman]

Hey, great result.

Was this the main fuel filter or the pre-filter?

 

[fwd]

main filter... I had already resealed the clear-pipe-to-prefilter and the prefilter-to-housing seals, hence did not look in that direction again... doh...