C250td... The Return of the Starting Woes

[thecrookedvulture]

Hi guys,

How are you all?
Sadly I am back with a new problem. Got in the car to go to work this morning and it started perfectly, first turn of the engine. Managed to reverse about 2m out the space and it suddenly cut out and refused to start again.
The engine is cranking but there is seemingly no spark at all. Had a similar issue about 6 months ago that was finally resolved by changing all the clear lines and the o-rings.
Any ideas? I'm stumped

 

[tode]

You have checked that fuel is coming out of the filter, and preheat works ?

 

[thecrookedvulture]

I will go and check that now. What is the best way of checking if the heat works?

 

[tode]

Better to start by checking that fuel is getting through the filter: in warm (?) weather, the engine should either start or cough even with no preheat.

Get someone to crank the engine, and try bleeding at at each point in the fuel line. The diesel should spurt out in a stream, not just drops +/or bubbles.

 

[thecrookedvulture]

Just looking at the car now. As i look at the filter, there is no fuel in the pipe on the left, which comes out the side of the filter. If i leave the car a few minutes, fuel will creep back along this line towards the filter.
I have also noticed that the pipes that come out the rear of the filter are fine, apart from the one on the right hand side which has an air bubble approx 1 inch im size at the top of the pipe.
Will try and get some photos

 

[thecrookedvulture]

Ok, heres a video i just shot

http://www.youtube.com/watch?v=m-Ud3JTb-T4&feature=youtube_gdata_player

Got some photos too, just trying to upload now

 

[thecrookedvulture]

(if you are wondering what i am trying to film immediately after the engine stops turning, i was trying to spot the scource of a strange noise I had not noticed before. Sounds like a Cricket!)

 

[thecrookedvulture]

Couple of photos;

http://www.flickr.com/photos/64390592@N07/sets/72157627114504405/

 

[tode]

It sounds as though it's not getting any fuel: 9 times out of 10 it's the filter. Try changing it (fill up new merecedes filter with clean diesel, check seal before mounting, and tighten up well, without forcing).

You could well have some air in the system, so when you start up, wait for preheat light to go out, then you may have to crank the engine for a while until the fuel gets to the injectors.

ps there is fuel in the tank ? (sorry :Oops: )

 

[thecrookedvulture]

Haha, yup there is definitely fuel in the tank
Will investigate the filter. At risk of making a fool of myself, do deisel models have a fuel pump relay, if so could it be that?

 

[tode]

The fuel is pumped from the tank by a small mechanical pump at the base of the injection pump (and is driven by it when engine turns over). The fuel is sent to the main filter and thence to the injection pump.

I don't know if UK 250s have it, but on mine there's a small prefiltre (clear plastic) on the line from the tank to the supply pump. Doesn't usually get blocked, but may be worth checking.

When you change the filter, it's a good idea to cut it open, and see just what was in it. I used to have a problem (on a 300) with the filter being blocked by water. Bosch gave me the tip to always keep the tank full, that way you get far less condensation, and less gunk in the fuel. Had no problems since (20 years)

Good hunting

 

[thecrookedvulture]

Awesome, thanks for the advice! One thing I have noticed is that just to the left of the filter housing, on the main cylinder block between what looks like two glow plugs, there is a small sensor of some description. It seems to be covered in oil, which could be affecting it I guess, do you know if this is anything related?

(Sorry for the awful description)

 

[tode]

No idea what that is Mines got quite a bit of oil as well. Probably meant to be like that to stop it rusting

 

[thecrookedvulture]

Anyone wanna buy a freshly sprayed (non starting) C250?

 

[tode]

No, but I can sell you a freshly starting (non-sprayed) one !

The problem will turn out to be something really silly. Work your way from the filler cap through to the injectors, and it'll start.

How many miles has it done?

 

[dieselman]

Anyone wanna buy a freshly sprayed (non starting) C250?

How much?..

 

[Simon21]

Just looking at the car now. As i look at the filter, there is no fuel in the pipe on the left, which comes out the side of the filter. If i leave the car a few minutes, fuel will creep back along this line towards the filter.
I have also noticed that the pipes that come out the rear of the filter are fine, apart from the one on the right hand side which has an air bubble approx 1 inch im size at the top of the pipe.
Will try and get some photos

Air leaks in the fuel line - that's why it won't start. Check all unions, O-rings etc.

 

[thecrookedvulture]

Hi guys, sorry for the delayed responses.
The car is now at the local indie, who has had it for a few days. Have just got off the phone to them, and they are thinking it is the lift pump.
Could anyone recommend a good place to get one? Are these expensive?

Cheers!

 

[tode]

Just a little after-thought: Before you hve any parts changed, try having the fuel line tank-lift pump blown through in reverse (from pump to tank). I had the case on a truck, which was impossible to start, and no fault found: somehow bits of paper towels had found their way into tank, and completely blocked the intake. It's a long shot, but always best to start right at the beginning and work your way through the system.

Also had the case of a filler cap blocked by dust: the tank ended up under vacuum, sucking the fuel back through the line when the engine was stopped.

Good luck with the problem.

 

[Alex M Grieve]

Just a little after-thought: Before you have any parts changed, try having the fuel line tank-lift pump blown through in reverse (from pump to tank). I had the case on a truck, which was impossible to start, and no fault found: somehow bits of paper towels had found their way into tank, and completely blocked the intake. It's a long shot, but always best to start right at the beginning and work your way through the system.

Also had the case of a filler cap blocked by dust: the tank ended up under vacuum, sucking the fuel back through the line when the engine was stopped.

Good luck with the problem.

good call. I like long shots like this - where practice can surpass theory. And it's cheap. And if it has happened before, who says it can't happen again?