w124 expert needed

[gt-83]

Guys, can anybody help me with a problem on a 1992 300ce
I have spent hours searching the net, and although i can find similar problems i cant find exact one as mine
This car starts instantly, everytime, then it idles lovely and smooth, temperature rises until the car gets to about 85 degrees the the car dies, when i say die i mean it is INSTANT as though the ignition has been turned of, no misfire just dead in a moment.
turn the key and she fires up straight away then runs with no problem
Its such a predictable problem, every time exactly the same
ive been reading other peoples problems that suggests all the usual, ovp relay, fuel pump relay, crank sensor and so on, i cant really afford to throw £££s away just buying bits randomly, and as its so predictable i thought that maybe somebody has a definite answer ...thanks for your time reading

 

[WG M-B]

There is no definitive answer. It's either losing spark or fuel, or its losing its idle position. Does it happen coming to a standstill?

 

[gt-83]

its as soon as it warms up, its not like a stall, it is so abrupt, but when you start it again its fine, like something is getting warm then making or breaking a contact but resetting itself after the ignition is turned

 

[gt-83]

Ive just been into the garage, the car is cold so i removed the air filter , started the car and waited for the temperature to rise, sure enough 85 degrees and it died BUT I WAS WATCHING THE ENGINE, the flap on the throttle body just dropped killing the engine, then rose again?????car started straight away again and ran no problem,,whats telling the flap to drop

 

[Harlowcabbie]

Could it be the crankshaft or camshaft position sensors I've heard they can fail at temp and that would cause the engine to shut down.

 

[mauno]

crankshaft position sensor. i had same symptom on a clk 55. replaced it and now its ok

 

[grober]

What you are seeing is the ECU sending a reverse current to the EHA [ electrohydraulic regulator] which drops the fuel pressure to the regulator shuting off the fuel supply. This is an overrun fuel saving measure. The ECU gets a signal from the throttle position switch mentioned above which tells it when the throttle is fully closed. There are other factors taken into account as to what engine rpm this happens depending on whether the engine is speeding up or slowing down but mainly influenced by engine coolant temperature!! It cuts off at lower and lower rpm as temp goes up. SO you could have a problem with the injection coolant temperature sensor, the throttle position switch the ECU or the EHA. My money like WG-MB is on a flaky throttle position switch unit or its wiring/connections. But it could be some weird combination of any of the above. What you are seeing is almost certainly fuel pressure cut off--- why its happening is another matter. What puzzles me is the intermittent nature of the problem

 

[Harlowcabbie]

Doesn't say intermittent he's reporting it does it as soon as car hits temp . I read it as every time the car is started it's ok until it reaches operating temp then shuts down .

 

[gt-83]

thanks Graeme for a very comprehensive reply, the fault is not intermittent, it happens exactly the same everytime the car is started

there is something i should add to this, if you would please comment
ive only just bought this car, from a guy who had this fault, he sold me the car along with a bill for 600 quid from his local garage who had fixed the fault apparently.....looking at the bill, im not sure they were familiar with these cars, anyway the seller is helping me out and being a real gent about the situation, he did mention to me THAT THE FAULT DIDNT OCCUR UNTIL HE JUMP STARTED THE CAR as you now mentioned the ecu, you have me worried that he has fried it?

 

[Harlowcabbie]

What did the garage repair for the 600 .

 

[gt-83]

work carried out
test battery
fit new battery!
test fuel pumps priming ok
strip down inlet side
remove and clean fuel metering head
clean inlet manifold
inspect all vacum pipes and electrical connections
fit new water temp sensors
fit new plugs
fit new cap
set up fuel air mixture
oh and the seller had new brakes all round

 

[grober]

One thing to try is to disconnect the EHA once the car has gone through its initial start up and started to warm up but not reached the "magic" 85 degrees. It will probably run rough when cold as its now lost fine mixture control but if it then goes past the point it normally cuts off you know the EHA is being activated to shut off the fuel. After that the first thing I would look at is the throttle position switch/limit switches to see if there's a problem there.

 

[balge]

Electronics are supposed to be very sensitive to problems caused by faulty jump starting, did they follow the procedure in the handbook?
Does the engine just stop or do all the electrics go off too?

 

[gt-83]

Thanks guys for all these replies,i do appreciate it, will try removing EHA in the morning

 

[grober]

Thanks guys for all these replies,i do appreciate it, will try removing EHA in the morning

DISCONNECTING! not removing.

 

[grober]

Right to clarify a bit, There are 2 sensors/switches on that car that tell the the ECU what is happening throttle wise. S29/2 that signals either full throttle or idle[ shut] for the throttle plate and S 27/2 is a microswitch on the throttle linkage that signals de-acceleration.

First try the EHA disconnect trick .

 

[stwat]

Jump starting the car can damage the OVP. It may even simply be that the fuse on top of it has blown.

I was having all kinds of similar running problems with my 300SE (same engine) A new OVP from Wunderpartz cured the problems instantly. It was only around £35 IIRC.

 

[martyz]

Check the fuse on top of the OVP relay,if intact check for dry joints internally,or THe ICV
(idle control valve) or associated hoses,or position of the AFM (air flow meter) flap,the
part you see dropping before it shuts down,this is critical, and if the garage has adjusted the fuel mixture it will have moved.any of these will give you the problem you are having.

The bosch KE injection system needs to be set by someone that knows exactly what they are doing.

 

[ray_hennig]

work carried out
test battery
fit new battery!
test fuel pumps priming ok
strip down inlet side
remove and clean fuel metering head
clean inlet manifold
inspect all vacum pipes and electrical connections
fit new water temp sensors
fit new plugs
fit new cap
set up fuel air mixture
oh and the seller had new brakes all round

I don't see a new distributor rotor arm there. My new, cheapo rotor arm caused a cut-out, albeit not as immediate as yours.

These engines demand the best in HT components so I recommend you ensure you have a good rotor arm, preferably from MB. Failing that, Beru or Bosch and NOTHING ELSE.

Not too costly so worth a try.

RayH

 

[gt-83]

Many thanks to all you guys that are following my problem, i need to update you.
there was a new cap and rotor arm fitted when the work was carried out (GENUINE)
i have checked both fuses on the ovp relay
first thing this morning, i swapped the ke unit for an exact part i had from a previous salloon car i had, just to see if previous owner had damaged it from jumping, start car , 85 degrees dead,
ok, so then on to Graemes trick of DISCONNECTING the EHA, obviously i had to wait for the car to go cold
start car, disconnect EHA, 85 degrees AND STILL RUNNING, dare i say it but it idles better with the EHA disconnected , it is much smoother when revved then back to idle,
do i need to have this connected?