My M103 3L only starts with kickdown
 

Hi,

I have a small but annoying problem with my m103 in my W124C; when the engine is cold I can only start the engine when I press the accelerator pedal until it "activates" the kickdown. Then the engine starts badly but it starts; it needs a minute or so until I can select a drive position; when I do it right after the start the engine slowly shuts off and can't barely start it again. Right after the start the rpm is at 600rpm; when I wait a minute it raises up to 900/1000; that's the moment when I can select a drive position and just drive. There is no blue or white exhaust noticable.



I checked the coldstart valve, replaced the relay that prevents overvoltage (OVP) with a new one and also replaced the fuelpump relay with a used one. There was no sign that the fuel pump relay was damaged as I could hear the fuel pump when I turn on the ignition and it just sounds good and normal but as it's a common problem I replaced it.

Some dude told me to clean the idle valve which is located near the induction elbow and flow divider. There was a lot dirt in it; I put 12V on it and it made a gentle buzzing noise; I put my fingers on both sides and couldn't feel anything but to be honest I don't know how this part works at all :). When I turn the ignition on it's buzzing for about 30 seconds and then shuts off...dunno if that's the expected behaviour. I expected it to be like a fan...it obviously isn't a fan.



When the engine is warm, after several miles, it starts immediately but shuts off slowly just like in the morning;



I always have to wait a minute or so after a successful start until I can select a drive position no matter if the engine is warm or cold. Steering the wheel also influences the rpm a bit but that should be normal.
The engine doesn't shut off in P and N.


What I checked:

- cold start valve
- OVP (it's brand new with two fuses now)
- fuel pump relay
- idle valve
- filter


Today morning I hardly could start the engine as it was a bit cooler than the last weeks and I got blue exhaust after a long try to start it (poor starter and battery).

I just own this car for a few weeks and simply don't know the details of the car; the pre-owner said he replaced all spark plugs, cables and distributor. The distributor cap has a small crack but that shouldn't be a problem, right?

Any help is appreciated.

Kind regards,
Andreas.

Just a quick response here but, in your shoes, I'd test the coolant temp sensor. It's cheap to replace and it sounds like a good place to start.

In my experience, HT problems don't effect cold start so much bit you should always make sure the HT is in perfect condition.

R

I recently went through similar symptoms with my 1986 300E. I replaced the idle control valve and the two hoses connected to it. The ICV should operate smoothly (not buzz) with 12VDC applied. The hoses are subject to high temperatures and get brittle and crack. I found a nice used ICV on ebay. Works like new.

Brent Smith
Atlanta, GA
1986 300E 278,000 miles

Icv should not buzz at all. It's a valve that flips open or closed to let in or block air into the intake manifold. When you apply 12v you should hear the clunk of it opening (and no noise as it stays open) and as you remove the charge it should spring back closed.

I know this problem, replace this sensor A0085423217 it tells the ECU the temperature of the coolant and if to use the cold-start.

Yep, air valve should flip open silently when power is applied, then close when taken away. I'd replace the sensor and air valve.

thanks for your help.

yes, that's exactly what it's doing; buzzing was a bit exaggerated; I just noticed it's "on" while it has 12V. My idle rpm is fine as well; engine runs fine, too, when it runs. On coldstart when I turn the ignition on it makes that clunk sound and after 30 (approx.) seconds it makes that clunk again and is "off" then. Is that the expected behaviour?

I checked the hoses; they are fine; not like a brick.

I assume A0085423217 is the coolant temp sensor, right?

Btw. I replaced all my spark plugs yesterday; replaced the Beru Ultra something with Bosch ones. It still only starts with kickdown but much better and earlier. The Beru looked brownish and were in good condition but the distance between the electrodes were bigger compared to the Bosch ones.

I am going to replace the coolant temp sensor and will report.

Thanks for your quick help.

Kind regards,
Andreas.

Hey, that's what I said! Hope it works.

R

hi,
I got the part but I couldn't remove the sensor as I don't have a fitting wrench socket (only short ones).

http://farm9.staticflickr.com/8444/7...b43d4273_z.jpg
Untitled by schipplock, on Flickr

However, I will get a fitting one today and report.

Kind regards,
Andreas.

this little sensor/switch fixed my problem :). The engine now starts immediately and doesn't shut off :). I can immediately select a drive position.

After I removed the sensor/switch it spilled approx. 2litre of coolant; I was a bit surprised but filled it up again and temperature is fine. Now I also own a tubular box wrench (what a stupid position this sensor/switch is at :>).

Thanks for your help.

Kind regards,
Andreas.

It's me again :).

Now I think the idle valve is broken, too :). Now that I know how it works...

Let me explain:

I turn the ignition on, I hear the clunk of the idle valve, I don't start the engine and wait approx. 30 seconds; then I hear the clunk again and the idle valve doesn't do anything anymore...when I turn the steering wheel to its maximum position and change the drive position at the same time while the engine runs, the engine shuts off; I can reproduce that every time; no matter if the engine is cold or warm. I can workaround that just by don't doing these two things at the same time.

As the valve is not the cheapest part (approx. 200 USD from Bosch), I'd like hear your opinion :). Do you think it's this valve?

I'm quite happy as my engine starts fine and drives well but sometimes when I leave the parking lot I don't think about this problem and select a drive position and turn my steering wheel to its maximum position and *boom* :).

Thanks in advance.

Kind regards,
Andreas.

just for your information: the fuel distributor was leaky; got replaced by another one that doesn't leak fuel and then it ran like it should.

However, the engine died on friday, 21st :(.