Poor starting when warm

[Crownhouse]

The car is a W140 1993 S-Class 320, straight six fuel injected. She's not a bad girl, but ever since I've had her (3 years) there has been one problem.

When Cold (or after she has stopped for more than 4 hours), she starts first time on the turn of the key.

Once the car has been warmed and I switch off the engine, she will start first time, but only if the period from switch-off to restart is not more than 1 hour.

If the car is warmed and the period from engine switch off to restart is more than 1 hour but not up to 4 hours, it is difficult to get her started. I will have to floor the pedal or crank (turn) the engine over for quite some time to get her to start.

Once the engine is well cooled after sitting for more than 4 hours, then the car will again start first time.

Engine runs smooth and idles like a big cat. I can not fault her but only for the problem I have just mentioned. She has been to two MB garages but they have no clue...IS THERE ANYBODY OUT THERE THAT CAN HELP???

 

[television]

If the only way to start it is with the throtle fully pressed, it means that the fuel is too rich, the fault will be in the fuel enrichment device or temperture sensors that control it.

Malcolm

 

[Stevie A]

Sounds like a faulty temperature sender. Should be cheap to replace. You can check them with a multi meter if you can find out the correct resistances at specific temperatures.

 

[jonnyb1]

Hi , i had a similar problem which we thought was a sticking alarm sensor on the car(door.....bonnet...etc) but it turned out to be a failing crank sensor. Hope this helps. cheers

 

[television]

Hi , i had a similar problem which we thought was a sticking alarm sensor on the car(door.....bonnet...etc) but it turned out to be a failing crank sensor. Hope this helps. cheers

.



Yes the cnank sensor is a know fault, on earlier cars there is a mod that alter's the spacing. With this fault you also get poor acceleration, and I dis counted it. there is also one on the camshaft.

malcolm

 

[Crownhouse]

Hello Guys
Please think about this.....I only have poor starting if I try and start the car anytime from 1-3 hours after it has been used.

Anytime from 0-1 hour after the car has been used it will start immediately.
Anytime more than 4 hours after the car has been used it will start immediately.

A very COLD engine starts OK.....and a very HOT engine aslo starts OK

Need your second opinions before I go off and start buying temperature senders and sensors and other devices...I AM VERY EXCITED

 

[Stevie A]

Test the temp sensors resistances with a multimeter before buying one. I don't know correct resistances for your car.

 

[television]

Hello Guys
Please think about this

They sell magic wands on Ebay.


Malcolm

 

[Crownhouse]

Thanks Stevie, I've got a new temp sensor and will be fitting it today. Will let you know how it affects the car.
Television !!! I was out bid. Bad luck. Anyway, what's your second opinion (senior member) ???

 

[television]

Television !!! I was out bid. Bad luck. Anyway, what's your second opinion (senior member) ???

I think that if pigs had wings, they could fly

malcolm

 

[Crownhouse]

I changed the temp sensor but starting is still as before.
Spoke with a chap at my local Mercedes Garage and he reckons I should first look for AIR LEAKS in the fuel supply (especially pipes) from tank to injector and back again.
Any Comments?

 

[RonH]

Had a similar problem with my 190 E.Would start first time when cold and when parked up some time, but would be a problem when parked up for a short time.Would turn over and over and not start, but would fire-up if throttle pushed to the floor and pumped.Checked most things and eventualy thought about it and deduced something was make the mixture too rich.
The cold start valve is temperature related and should only come into play for a few seconds, at most, when the engine is cold.
To cut a long story short I replaced the cold start valve and cured my problem.It seems the valve must have been leaking slightly wnen it was supposed to be shut.Consequently, when the car was parked up the valve was dripping a small quantity of fuel into the air intake and so making the mixture too rich for starting.When cold, the rich mixture didn't become a problem, it was only when the engine was still hot that it threw out the mixture and caused my starting problems.
I haven't a clue as to if your car has the same set up, but you may have something similar.Anyway something to think about !.

 

[doogle]

I had the same symptoms on1995 e220 the answer was to replace the fuel pressure regulator.
doug

 

[shayes]

I changed the temp sensor but starting is still as before.
Spoke with a chap at my local Mercedes Garage and he reckons I should first look for AIR LEAKS in the fuel supply (especially pipes) from tank to injector and back again.
Any Comments?

Have you solved the problem yet?
Interested to know as have similar problem on my SEL500.
Believe Ron H must have hit the target, but cold start valve a mighty expensive piece of kit?
My uneducated theory is that when the car has been running and is switched off the residue of pressure in the injectors somehow leaks out into the pots and wets the plugs, thereby causing difficult start after engine has cooled but not sufficiently dried out. Does cleaning the injectors prevent this and therefore this is the answer? Have to say that I am unfamilier with the exact mechanism of injector workings so possibly a lot of balderdash!

 

[russell-wheeler]

warm start

i had exactly the same problem on my 88 300te. 167k
changed cold start valve etc and metering head unit to no avail

put new injectors in (12.50) ea from eaby - starts 1st time every time and does better mpg

didnt think it would be the injectors because apart from poor starting the car ran fine - just hot starting was a pig - 30 seconds of cranking with foot to the floor and massive smell of petrol when it caught.

 

[shayes]

Replace injectors - £12.50 each - is that ebay?
Just had a quick look and £13.95 + £9.99 postage but not for my model.
Euro (from???) £21.05 each.

Is it possible to clean injectors once removed? Can try a fluid cleaner in the petrol but not sure if they are recommended. STP do one I believe?

 

[television]

Replace injectors - £12.50 each - is that ebay?
Just had a quick look and £13.95 + £9.99 postage but not for my model.
Euro (from???) £21.05 each.

Is it possible to clean injectors once removed? Can try a fluid cleaner in the petrol but not sure if they are recommended. STP do one I believe?

Stuart, I will get your relay back to you on Monday and I will give you a hand with your problems.
Regards Malcolm

 

[russell-wheeler]

I tried the injector cleaner - it didnt harm - didnt work either tho !

MERCEDES BOSCH INJECTOR 201 124 126 107 129 123 460-1
Item number: 6627863288
Ebay code for the injectors - they are always on - most of the mechanical fuel injection systems in the mercs seem to use the same injectors - but make sure 1st !!

 

[shayes]

Thanks for the info

 

[shayes]

Stuart, I will get your relay back to you on Monday and I will give you a hand with your problems.
Regards Malcolm

Thanks Malcolm