Loss of power W124 E250diesel

[lukebowman551]

Hi, i have a bit of a problem and was wondering if anyone could help?

I have a W124 E250 Diesel.

I was driving along the motorway to visit my girlfriend in London, about 150 miles. During the journey on about 4 or 5 occasions i felt a loss of power (like when you run out of fuel) when i set off home the next day i struggled starting the car (fired up but wasn't revving properly). The loss of power thing happened 4 times on the journey home.

When i opened my fuel cap there is a surge of air, so i think that maybe air isn't getting into the fuel tank and therefore creating a vacuum that's stopping the fuel?

Not sure though, any ideas anyone?

 

[Howard]

Not sure about the fuel tank ...

Mine does that as well ( big hiss when you open it , especially if fuel is low ) , i asked on here about it, and am led to believe that the w124 fuel system is pressurised or something ...

It is quite normal for a big hiss to come from the fuel tank when you take the cap off.....

 

[bolide]

Is it a 250TD or an E250? I'll assume it's the latter with the multivalve engine. I'll also assume it's non-turbo car (early LHD cars were turbocharged)

I'd start by checking for diesel leaks under the bonnet. Then I'd try replacing the fuel filter & the fuel pre-filter and see if that cures the problem. If not I'd look for crud in the fuel tank, air leaks in the pipework or injection pump / engine problems

Poor starting is normally caused by air leaks. Search this Forum and you'll find lots of information reagrding this. If you have air leaks you can usually see the air bubbles in the clear fuel pipes by the fuel filter

Another possibility is that the fuel-feed shutoff is only opening partially. The early cars would do this but the later multivalves have a different design of shutoff valve. I've not seen a problem with the shutoff valve on a multivalve yet

Nick Froome
www.w124.co.uk

 

[lukebowman551]

Ok, so the hiss is normal, it did seem to come out of the tank rather than air rushing in to be fair.

I have noticed a fuel leak from the fuel pre filter. I'll try replacing this.

Does this definately seem like air getting into the system then? even whilst on a long journey?

 

[bolide]

I think nothing's definite. You'll have to find the problem(s) by a process of elimination

Also the manual shutoff valve (if it's a multivalve) screws into the top of the fuel filter. If it leaks, replace it

Nick Froome
www.w124.co.uk

 

[lukebowman551]

yeah it is the multi valve non turbo. i'll have a look at these things and see what's what. Cheers for the tips. Luke.

 

[Dieselman]

Luke
It will be air entering the fuel system at the filter-head. Dont forget a diesel fuel system is under vacuum until the lift pump on the side of the pump body.
If fuel is leaking air will be able to get in.

 

[lukebowman551]

i can see air bubbles in 2 of the clear fuel lines around the fuel filter, should i replace these?

 

[Dieselman]

Try revving the engine whilst watching hte fuel lines. If air is sucked in then definately replace the pipes. This is the most common failing on the OM605/6 series of engines.

 

[lukebowman551]

I can see air in the 2 lines going from the filter to the pump. Also leaking out of the line that enters the pre filter.

 

[Dieselman]

I can see air in the 2 lines going from the filter to the pump. Also leaking out of the line that enters the pre filter.

Ker-ching!

Now just be a boy scout and get the "job done!"

 

[lukebowman551]

I've replaced the fuel line going into the top of the pre filter and this seems to have solved the problem, cheers guys.