E300D won't start (sometimes)

[R Phillips]

I have isolated it to being low on fuel (just under 1/4 tank) and being parked slightly uphill. Is their a non return valve in the fuel line?
It does start but takes a good minute or two cranking over.

 

[230K]

Hi

Not sure if there is a non-return valve but you can fit one. Most probably your problem stems from air getting into the fuel system via the plastic preformed hoses that are scattered around the fuel pump and filter,could be as many as 6, the seals at the ends of these hoses start to suck air (mostly no diesel leak can be seen). Best to renew all of the hoses, dieselman will explain how many there are, he has advised covering the connections of these hoses with grease to stop the air being sucked in. The inlet manifold might need removed to renew one of these hoses but that is not that big of a job..

Also people working around these engines yend to move the connections and upset the seal, have you had any work done recently?

Good luck,

230K

 

[pascal]

There was a thread here a month or to ago about this.

The fitting of the non-return valve did not solve the problem. Although where it was fitted, I am not sure.

Agree with 230. Air leaking in.

 

[Bolide]

E 300 Multivalve Diesel won't start

I think everyone's on the right track. I've had this problem too on my 1994 E300 (multivalve) diesel but not with any customer cars yet!

Air leaks into the system when the car's parked nose-up and it takes 10-40 minutes of cranking to push the air out of the system, crack the injectors & start

On my car I think the leak is in the shut-off valve on top of the fuel filter. It can also be caused by air leaks at the joins of the many clear fuel pipes round the filter & injector pump. You can buy new O-rings for these pipes from a dealer and I suggest you replace them all. The O-rings compress with age, go flat in section (rather than round) and leak. There are two sizes of O-ring - get half-a-dozen of each and replace all the ones you can get to

Be aware that disturbing the fuel system on these cars does cause problems with air leaks. And when this happens they are ****** hard to start!


Nick Froome
www.w124.co.uk

 

[shrekky]

sometimes it can be hard to find where it is sucking air in,just have to persivere,start with the easy to check things like fuel filter holder,and fuel lines,look at the front seal on the pump and work backwards replacing all seals and double checking all joints..............you mention.just under 1/4 tank,does it only do it then ?.........if so could be a fuel pick up problem...........in that when you are parked nose up....fuel moves away from the fuel pick up pipe and allows air into the lines,thus allowing fuel to flow backwards...........just a thought :-?

 

[fivenil]

As a new member I am seeing if anybody is still looking at this thread. My problem is identical - had a 1/4 tank - won't start if pointing uphill (neighbours do wonder why I park the other way round these days!). I am going off to replace all hoses and rings, but I am struglling to get my head around why the amount of fuel in the tank affects air leaking in pipes under the bonnet.

Can anybody enlighten me?

 

[Parrot of Doom]

At a guess, probably because air compresses more readily than liquid fuel? More fuel in the tank = less volume of air to compress under gravity = less fuel drains from fuel lines = less air gets into fuel lines?

 

[Bolide]

I would think the answer lies with the relative heights of the fuel feed & return. The MB retrofit kit (£10-odd) has two non-return valves so I suspect one valve is fitted in the return

If the fuel level in the tank drops low enough to expose the return, and there's an air leak up front, the fuel in the return line will drain back. Same goes for the feed, but if the feed is exposed the engine's getting no fuel anyway. If the level of the fuel covers the return outlet then it won't drain back

That's my theory anyway!

Nick Froome
www.w124.co.uk