M103 Starts and Dies then Starts OK

[bigblue1]

I have a 1989 W124 purchased last year at 134,000km and now with 143,000km.

The car is perfect other than the fact it has a tendancy (usually when warm) to start and then die then always starting perfectly on the 2nd attempt.

On the first attempt the engine will burst into life finding 1000-1100 rpm then fall, failing to hold idle speed, back to 0 rpm.

The car has been serviced and tuned with all new plugs, air filter etc. by a Merc specialist. I even had the fuel accumulator checked out last service. Car is run on premium fuel. Compression was checked out on purchase and otherwise the performance of the car is excellent.

My service guy suggested that the injectors may need to be replaced.

I note that in Stu Ritter's E Class Bible he mentions what might be this problem under 'Driveability (M103 Engine)' page 143, the fix being to adjust fuel distributor lower chamber pressure to effectively richen the mixture.

Has anyone experienced and fixed the same problem or can suggest otherwise?

Ultimately it may not be possible to have have eveything perfect but no harm in trying

Thanks

[terminator]

I have fixed this problem on mine but not on purpose. When I replaced my injectors I all so did the fuel distributor, injector lines, fuel pressure reg. and check valve. I did all of this because I had a bad idle that would not go away. When it was all said and done the car ran great and it starts on the first try anytime. I would start with the injectors first, the worn ones have a tendency to leak down when parked warm. Hope this helps!

[bigblue1]

Thanks!

This seems to make sense the more I think of it.

Having the correct information to throw money at the right place is key with these older cars.

Out of interest what did that 'little' fuel system service you did cost?

[terminator]

I work for a MB dealer so I think my cost was some where under $2000.00 with me doing the labor.

[ako]

Bigblue1,

My M103 engine has the same problem as yours. Compression is perfect as per Enrique of Mr. MB Motors. No vacuum leaks found. Spark plugs, distributor cap and rotor are new. No fuel leak found. I tried Techron fuel injector cleaner three times but to no avail.

Our only difference is that in my M103, the engine dies when starting from a cold start. And on the first 0.5 seconds of cold start, the engine is a bit rough. But when I restart it, everything is fine. On a warm start, the engine doesn't die like yours does.

I also notice that my engine consumes about 25% more gas since this ordeal started. I haven't really tried Stu Ritter's advice on page 143 of E-Class Owner's Bible.

Please let me know when you find a solution.

Thanks,

RV
--------------
92 300 TE 127K miles

[Duke2.6]

This is somewhat typical of these engines, and you can spend thousands chasing this ghost or just modify your operating habits by giving it a bit of throttle right after it starts on a hot start.

This condition can sometimes be tuned out by adjusting the duty cycle to a lower value to achieve a slightly richer base mixture, but if it cold starts okay, this may not help.

I consider an idle duty cycle of 45-50 percent to be ideal, but if starting behavior is a problem - either hot or cold an idle duty cycle of 40-45 percent might help.

Duke

[bigblue1]

Thanks Duke

I don't understand 'duty cycle'.

I have tried using the accelerator trick that is a bit hit and miss. Sometimes you can catch it however it is probably a matter of putting on a bit of accelerator in the first place.

My experience with doing this is creating a backfire. Do you think this is a problem?

Do you also think that fuel injectors are the likely major problem for starting / idling problems. These items must have a finite life and several posts appear to discuss the matter with some success.

Normally the problem doesn't bother me as when I start it to go to work and come home from work it fires right up on the cold start.

In the last few days I have been driving around a visitor and every time you get back in it takes two starts!!

If you restart within a few minutes it will start so that leads me to think even more the problem is with leak down from an injector/s in between the time of an imediate restart and when the engine is cold enough for the cold start function to kick in.

Thanks

[Duke2.6]

www.landiss.com/mixture.htm

My C280 did the same, fixed with a new OVP.

[bigblue1]

What is OVP and what does it do?

Is this applicable to a 1989 W124 / M103?

Thanks