Fuel

[Merc]

Hi

I'm not sure if I mentioned this before,but I was the site in the States, that Anthony had mentioned (not bad at all!).But I was looking through diffirent things and came accross this,someone had just driven about 160 miles then stopped,they tried to start the car again and it wouldn't!,it did eventualy start,but he was miffed.
The replies he got were look at/change the fuel pump.
The reason I'm asking is that the same kind of thing happened to me,only it happened when mine was up on the ramps at ATS getting my wheels/steering checked,when I just got it,but could it be the same thing on mine?

regards

 

[Anonymous]

More likley to be the relay.
It has the word "Kickdown" on it, I believe, and the date it was manufactured.

Will

 

[Merc]

Hi

I'm gonna sound dumb here!,but a relay, or is it because the relay is the simplest to check/change first.
Where is it?,is it under the bonnet to the left at the bulkhead in the "black box" with the fuses,I know you say it has "kickdown" on it,so I'll have a look.
But can this bugger cause' all thats been happening?,I take it,it controls the pump,so if I replace this and it still does it,then its only the obvious thats left,I just didnt expect there to be a relay for that,thats all!.

Regards

 

[Matt Crooke]

Sounds a bit like fuel evaporation/starvation, have you checked filters etc?

 

[dave elcome]

Probably fuel in the manifold evaporating with the heat of the engine.

 

[Merc]

Hi

I would have thought if the fuel evaporated then the chambers would be empty,so therefore it would start!,unless as you say starvation eg-fuel pump/relay nackered.
So can I rule out the dizzy cap/rotor!.

Regards

 

[Merc]

What I meant to say also was,why does it only do it when you stop,I mean if it was the pump ect,why does it run ok otherwise.
I would have thought if something like that was buggered the car would run or stutter/choke at all speeds,or is that theory wrong!

regards

 

[Anthony Banos]

Hi Merc & others

This problem occurs particularly after the engine has been running due to the pressure relief valve located at the back of the pump inside. It is activated by a small spring which in time weakens and do not allow pressure to be relieved.

As the pump is driven by a permanently excited electric motor (when the engine is running) the pressure is reduced. After stopping, the fuel reservoir maintains pressure in the system to facilitate starting and with this pressure if the valve is stuck it develops and inner leak.

When this happens, if you tap the pump firmly it releases the pressure valve and the engine starts again.  When the tapping affair becomes more frequent, it is time to replace the pump.

However, Mercedes have realised this problem and they can provide a check valve to be installed by replacing the hollow screw on the fule line in the direction of the engine with a secondary relief valve so you dont have to buy a new pump. (£4.75 for the check valve)


(Edited by Anthony Banos at 12:30 pm on Feb. 19, 2002)

 

[dave elcome]

Thats a mod worth knowing about!!

 

[Merc]

Hi guy's

yep,thats what I thought too,I'll get that checked out!.

regards

 

[dave elcome]

Merc.

At that price you may as well just do it, it will certainly be the least you have spent recently!!

 

[Merc]

Dave

Thats what I thought too.

regards

 

[Andy]

Hi

This mod was for vehicles that when hot, and the engine left for a few minutes it would take a while to start again.  While spinning over. Most of your vehicles hear have that mod fitted. I doubt that the problem is this but I suppose it could be. But read the answer I have given in an earlier post.

Also if your vehicle isn't fitted with this one way valve, you will also need a cap. Check with your MB dealer and they should be able to point you in the right direction.

Regards

Andy @ www.mercedesservicing.com