C250d cold start problem/now cutting out.

[Gazza'b]

Hi there,

I have a 1995 C250d which I love to bits but is now giving me loads of grief.

Problem started when trying to start car after being left overnight. It was taking lots of cranking (about 15secs) before it would fire up. After that the car was fine the rest of the day.

After reading various threads in here I thought it was the old 'air in fuel lines/o ring problems' whereby fuel was running back into tank. Took car to local garage/mechanic who is an ex Merc mechanic. Stated he used to get this prob lots when we worked for Mercedes.

Anyway, here's what he's tried to date:

O rings replaced, including one for pre filter. He assures me he's replaced them all. Prob still existed so;

Put in non return valve & car worked fine for them. When I went to pick car up it wouldn't start so;

Put in lift pump. I picked car up but it cut out on me after 40miles. Bit concerned as up to this point it had only been a prob with a cold start. Car had never cut out before in 3 years of ownership;

Put in new fuel shut off solenoid. Car still cutting out.

Any ideas or suggestions(clean ones) I can pass on to the mechanic. I'm a mechanical numpty myself & the spiralling cost of parts is getting me very worried indeed.

Cheers
Gary

 

[Number_Cruncher]

If you look at these piicies of the low pressure fuel pipework;

http://www.detali.ru/cat/oem_mb2.as...GM=717.417&CT=M&cat=19S&SID=07&SGR=120&SGN=04

The front injectotor leak off pipe #146 connects to a tee piece. The stub of this tee piece which points towards the back of the car is the fuel return to the tank.

If you insert a length of clear pipe in here, and watch during cranking, you should see fuel being sent back to the tank.

If you don't see fuel moving, you need to identify why.

One distinct possibility is that the electronic diesel fuel injector pump and/or fuel shut off valve isn't being commanded properly by the engine management unit and immobiliser.

It sounds like your garage is rather poor, and is trying to fix the car via poke and hope methods** at your expense, rather than trying to find evidence before asking you to buy parts.

** Alas, this has always been a problem, both in the trade and DIY, but the consequences are a bit more expensive nowadays.

 

[brianbrian]

Have you checked glow plugs and relay, Hope this helps.

 

[Gazza'b]

Thanks guys, the car was recently serviced at a different garage & glow plugs/relay was checked then.

Car has been struggling to start in morning for a few months now, progressively getting worse. It just got to the stage where I thought I'd try get it sorted once & for all. Put it into current garage as they stated they were Mercedes specialist.

Begining to wish I hadn't bothered now, as what started off as a 'bad starting' problem has turned into a 'cutting out on me' problem.

 

[Number_Cruncher]

Are all the low pressure fuel pipes connected *exactly* as per the diagram.

Quite why MB have made the fuel routing so complex is beyond me, but, it is possible to assemble the pipes incorrectly.

 

[Gazza'b]

Unfortunately I don't have the car at present as it's in the garage over the weekend.

If memory serves me right however, they are as the diagram but I will check.

Thx.

 

[turbopete]

has the tank strainer been cleaned/changed? if its blocked it will mean reduced fuel getting through to the ngine, giving poor starting and when fuel demands are higher, possible cutting out! a problem ive had many times on farm vehicles filled with less than clean fuel from storage tanks in the farmyard! also, when the car is running and revved up slightly (to around 1200-1500 rpm) is there any air visible flowing through the clear plastic pipes near the fuel filter? my car has a similar problem./ poor starting after standing for only a few minutes and if driven hard then the engine is stopped, it refuses to start for about an hour afterwards. new strainer ordered for fitting next weekend!

 

[Gazza'b]

Didn't even know it had one (strainer), shows you how much I know. I'll pass info onto mechanic so he can check.

There's def air bubbles in the clear fuel lines. Car had never cut out on me before garage put in non return valve & lift pump & I've had the car for over 3years. I'm wondering if the car either doesn't like this valve or maybe the o ring at the lift pump needs replaced.

 

[turbopete]

theres an o ring behind the cut off valve for the fuel that i had to change on my e class. never had any problems with my c-class cars. tank strainer is at the bottom of the tank and is just a screw in item. non return valve shouldnt be a problem as long as the pipe unions to it are air tight! new lift pump is probably pulling fuel from the tank much more efficiently and therefore pulling all the dirt and sludge thats accumulated in the tank over the years to the strainer, effectively blocking it, causing fuel starvation and low pressure for initial starting. thats the thinking im using for my problem, and yours sounds remarkably similar as far as symptoms go! just dont think mines bad enough for the engine to cut out when driving yet!

 

[Gazza'b]

Cheers, makes sense. Hopefully that's all it is.

 

[Gazza'b]

I'm now mobile again.

Appears there is (or was) a problem with the tank. Mechanic states that drivers side of tank was empty tho other side had fuel(there was about 10 litres in tank at this point), hence fuel starvation, hence car cutting out. He recommends that I drive with at least half tank diesel in it. If feeling brave I can try run it down to 1/4 tank. Prob not sorted but it's a solution in meantime.

If anyone has a diagram where the strainer is I would appreciate it, so I could maybe check this.

Car starting first time now in morning. Appears glow plugs were gubbed, even tho they were checked/replaced at start of winter. Don't know if long cranking, cold winter or some other fault caused this.

Amount of air bubbles in fuel lines is now minimal compared to what it was, so think replacement of o rings helped here.

 

[television]

There does not seem to be one in the tank, but there is on the fuel pump package 26 in the link

http://www.detali.ru/cat/oem_mb2.as...GM=717.417&CT=F&cat=44V&SID=47&SGR=030&SGN=02

This is all behind the rear off side wheel behind a plastic cover


The tank is shown here but no filter

http://www.detali.ru/cat/oem_mb2.as...GM=717.417&CT=F&cat=44V&SID=47&SGR=015&SGN=01


the fuel lines are here

http://www.detali.ru/cat/oem_mb2.as...GM=717.417&CT=F&cat=44V&SID=47&SGR=045&SGN=03

 

[BOBFAIR]

Bobfair

Hi, I am having the same problems with my C250D .Until you can find the problem try filling the tank right up. Then see if it will start in the morning. Regards Bob

 

[television]

Hello Bob and welcome,,so you are having the same problems

 

[GeoffBW]

Hi, sorry to resurrect this thread but am having similar problems with my C250D so decided to check out the fuel strainer but can't find it! Looking behind the rear o/s wheel in the boot, I can find a black plastic box in a foam rubber casing with some electrical wires and a yellow pipe coming out leading to a red plunger - doesn't look like a fuel pump package to me? In the side wall, there's a black plastic grid with flaps in it but that just seems to be some sort of ventilator. Can anyone point me in the right direction? Many thanks, Geoff