Mystery

[IanA2]

I don't know if this is the right place for this post, if not I'm sure it will be moved.

Story goes like this: I sold my 95 plate C220 Elegance to a guy I know. Sold it for £2,200 which I thought was a good price for him. I have had virtually no problems since I bought it at about 14 months old. Since he has had it he has had problems. Symptoms seem to be that it runs fine then just fades out.

Leave it, it starts again, runs well, then fades and stops again.
He took it to a local "back street" mechanic who diagnosed a faulty air flow meter. This was replaced, made no difference. He then took it to another "mechanic" who said the coil & HT leads were knackered. They were replaced. Same problem.

Despite not having MB diagnostics, this mechanic says that he has asked an "expert" (who has not seen the car) and this "expert" says it is a CHIP/EMS problem. He is also saying that it has happened before!!!

It is being taken (today) to a Merc specialist. Has anyone come across this before? In the back of my mind I seem to remember a coment "Honest John" made about water in fuel pipes that could cause "steam blocks"....ring any bells?

Realy grateful for any advice................

One thing I have learnt, however confident you are of the car you are selling, don't sell to someone you know, or a neighbour, or in my case both !!

 

[Thmsshaun]

Oh sold mine to a friend was a bit reluctant but went for the quick sale. said I would give it 12Months MOT and today it went straight through. Panic over I was dreading big bills.

Sorry I cant help with the problem just looks like a good job you sold it.

 

[Dieselman]

Definately not your fault or problem. The buyer saw you driving the car regularly and purchased as a result of that.

The problem sounds fuel related. How often does the power drop away?

It could be the fuel pump losing pressure.

It needs the diagnostics read.

 

[Vlad]

For the sake of your sanity and keeping good relations going, get the car booked into a decent Mercedes Indi and get them to go over the car and diagnose the problem.

If he keeps taking it to various non Merc specialists, he will continue shelling out money and getting more and more hacked off with the car and you, even though its not really your problem any more.

Where in the country are you?

 

[IanA2]

Definately not your fault or problem. The buyer saw you driving the car regularly and purchased as a result of that.

The problem sounds fuel related. How often does the power drop away?

It could be the fuel pump losing pressure.

It needs the diagnostics read.

Thanks for response. Yes it truly was a very good runner, we were a bit reluctant to let it go. It seems a bit intermitent as to when it fades out. After the second "mechanic" replaced the coil and leads it seemed to go ok for about 30 miles. When it was picked up from this "mechanic" it went for about 3miles. Mystery is that it runs perfectly when it does.....apparantly it just fades out as if no fuel is getting through.

 

[IanA2]

For the sake of your sanity and keeping good relations going, get the car booked into a decent Mercedes Indi and get them to go over the car and diagnose the problem.

If he keeps taking it to various non Merc specialists, he will continue shelling out money and getting more and more hacked off with the car and you, even though its not really your problem any more.

Where in the country are you?

Would you believe I suggested he take it to a local (ish) Indy from the word go? I think he was trying to save money. It's now with the Indy (who I know and trust) so we should soon know.
NE Northants.

 

[prprandall51]

Whilst this problem could be many things, it has all the symptoms of a blocked fuel tank breather.

As fuel leaves the tank, air has to replace it. If the breather is blocked, a vacuum builds up over a period of time preventing the fuel pump from supplying fuel to the engine - the engine slowly fades away because of fuel starvation. If you stop the car and leave it for a while, gradually the air gets back into the tank and then the car works again. For a while.

A good check for this problem is the moment the car has faded away, remove the filler cap. If it comes off with a sighing sound - that is the air getting back into the tank. Sometimes the filler cap can be difficult to remove because it is physically held in place by the vacuum in the tank.

Some particularly vigorous fuel pumps are capable of creating a strong enough vacuum to implode the tank (not explosively).

Good luck.

Philip

 

[IanA2]

Whilst this problem could be many things, it has all the symptoms of a blocked fuel tank breather.

As fuel leaves the tank, air has to replace it. If the breather is blocked, a vacuum builds up over a period of time preventing the fuel pump from supplying fuel to the engine - the engine slowly fades away because of fuel starvation. If you stop the car and leave it for a while, gradually the air gets back into the tank and then the car works again. For a while.

A good check for this problem is the moment the car has faded away, remove the filler cap. If it comes off with a sighing sound - that is the air getting back into the tank. Sometimes the filler cap can be difficult to remove because it is physically held in place by the vacuum in the tank.

Some particularly vigorous fuel pumps are capable of creating a strong enough vacuum to implode the tank (not explosively).

Good luck.

Philip

Thanks, apparantly that has been tried, to the extent of running the car without the filler cap! So probably not that.

 

[grober]

BAAAD fuel?

Partially blocked fuel filter?? Water in fuel? You might have to drain/.flush the tank/pipework Might explain why its intermittant as it might only happen when tank is near empty?? Symptoms sound fuel related rather than ignition.Ask your friend if he filled up at any unusual petrol station-small independant or on holiday? Just my 2p worth

 

[Shude]

moving to engine section

 

[Howard]

Hmm, reading this has made me think ......

Sorry to hijack your thread slightly Ian...

My w124 coupe , when i fill up , when i undo the filler cap, there is a huge hiss, just like you have described, however there is no problem with the running of the car.... should i be concerned about this ?

 

[Shude]

My w124 coupe , when i fill up , when i undo the filler cap, there is a huge hiss, just like you have described, however there is no problem with the running of the car.... should i be concerned about this ?

You could try a new cap, they cost peanuts.

 

[Howard]

Thanks Shude...... the cap looks fairly new, its in great condition (still very shiny ) and i have looked at it closely, doesn't seem to be anything wrong with it .....

Theres no problem with the car ... i was just curious .....

 

[Sp!ke]

Thanks Shude...... the cap looks fairly new, its in great condition (still very shiny ) and i have looked at it closely, doesn't seem to be anything wrong with it .....

Theres no problem with the car ... i was just curious .....

Mine has always been this way... no problems either. In fact, mines almost feels as if the fuel delivery is made by pressurising the tank rather than by normal fuel pump means.

 

[Howard]

Thats what i was trying to say Sp!ke, but not putting my thoughts into text properly , when the cap comes off it feels like air is rushing out under pressure, rather than rushing in to fill a vacuum ....

If theres no worries then i shant fret over it

 

[Shude]

Thanks Shude...... the cap looks fairly new, its in great condition (still very shiny ) and i have looked at it closely, doesn't seem to be anything wrong with it .....

I did wonder about ordering the chrome W124 cap, the W202 cap is a black plastic thing and I know the one from the W124 fits because I tried it

Will hit the catalogue if I get chance

 

[Vlad]

Howard just like your CE, all of my W124's hiss when I take the fuel cap off.....pressure coming out.

 

[Ian B Walker]

same with both mine and the 200T and 190E before it

 

[Dieselman]

Thanks for response. Yes it truly was a very good runner, we were a bit reluctant to let it go. It seems a bit intermitent as to when it fades out. After the second "mechanic" replaced the coil and leads it seemed to go ok for about 30 miles. When it was picked up from this "mechanic" it went for about 3miles. Mystery is that it runs perfectly when it does.....apparantly it just fades out as if no fuel is getting through.

Sounds like the fuel pump or OVP relay is on the way out.

If the car plays up this often then it should be easy to diagnose.

Two things need to be known. Is the power getting to the fuel pump consistently and is the fuel system staying under pressure.
In addition check the connections onto the fuel pump, both positive and negative connections.

"special" test equipment required...multimeter and low pressure gauge.

This doesn't sound like a major problem but unvortunately the new owner is taking the car to "GuessFix mechanics.Inc."

 

[IanA2]

Sounds like the fuel pump or OVP relay is on the way out.

If the car plays up this often then it should be easy to diagnose.

Two things need to be known. Is the power getting to the fuel pump consistently and is the fuel system staying under pressure.
In addition check the connections onto the fuel pump, both positive and negative connections.

"special" test equipment required...multimeter and low pressure gauge.

This doesn't sound like a major problem but unvortunately the new owner is taking the car to "GuessFix mechanics.Inc."

"GuessFix & f*** up mechanics.Inc." methinks. Somebody else suggested it might be low fuel tank/cheap fuel. I think both are likely to be true with new owner. Personally I always filled the tank when down to half full and used Optimax.