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  #1  
Old 07-26-2001, 12:52 PM
agupta
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Hello Everyone,

My 190E 2.3 (85, 118K) is driving me nuts - have shown it to 3 techs (incl dealer), spent $2K over the last 6 months, and it keeps getting worse!! I have read as many responses from the archives, but to no avail. Please help!

Since yesterday, the car is giving problems while starting cold. Had to crank it 15 times yesterday, 4 times today. If it hasn't sat for more than a couple of hours, it starts right up. So no problem starting when warm. Have never had this problem before.

However, for the last 6 months, I have had another problem as well (and still do!) - the car runs and idles rough when the engine is cold (first 5 minutes or so). When cold, it really hesitates, no power, no pickup. Has a "slingshot" response - suddenly it clears up and runs smooth. At that time, I hear a loud clik from the engine, driver side, bottom - can even feel the click in the accelerator pedal. This happens 5-10 times before it finally smoothens out. When it smoothens out for good, I can distinctly notice it - the car lunges forward. On hot engine, the car runs (and starts) ABSOLUTELY smooth - no problems at all. Fuel consumption is up 20%.

Have shown it to a dealer, and two MB techs in my area (Cleveland), but the exact same problem still remains - no change AT ALL. Have changed plugs, wires, distributor cap/rotor, injectors, air/fuel filters, thermostat, OVP relay has been changed twice. Nothing has worked, nobody seems to have understood what's going on, meanwhile I am stuck with an unrealiable car and a 2 grand bill!

PLEASE HELP! what should I do next? Are the two problems linked (cold starting and cold running)? In the previous threads, there were mentions of changing the coolant sensor, cold start valve, fuel pump, fuel pump relay, air flow sensor, EHA, etc. Obviously, not all could be malfunctioning - what should I ask the techs to do (in terms of diagnostic tests)? How can one zero in on this problem? What symptons can I notice as a layman, which can point me to the right direction?

Sorry for the long post, but I'm really at my wits end, totally frustrated, and would appreciate any comments you may have.

thanks a ton,
Rags
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  #2  
Old 07-26-2001, 12:55 PM
agupta
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Another symptom with the cold starting problem - when it does start (after many cranks), it runs really rough for 30 seconds or so.

Rags
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  #3  
Old 07-26-2001, 07:21 PM
Clauser1
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Of all the things youv'e changed,You have never mentioned
the ignition coil.Maybe thats your problem.
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  #4  
Old 07-26-2001, 09:43 PM
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. . . and don't forget

the cold start valve! If it leaks it will give the symptoms that you describe.

My '91 190E 2.3, did the same thing. Took a while to 'track' it down (because it would act ok sometimes!) but it was leaking causing flooding, thus hard starts.

[Edited by JimF on 07-27-2001 at 11:49 AM]
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  #5  
Old 07-26-2001, 10:05 PM
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I would monitor EHA current and differential pressure. One follows the other. They are the window to real diagnostics of this system. The EHA current should be standard op procedure, but monitoring the diff pressure takes knowing what to look for and its an uncommon test (though specifically laid out in the Diagnostic Manual).
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  #6  
Old 07-27-2001, 12:45 PM
agupta
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Thanks for the posts so far.

Another symptom is - the number of cranks needed to start the engine is directly proportional to how many hours the car has been sitting - after 5-6 hours, it needs 2 cranks, after 12-14 hours, about 4-5. Secondly, while cranking, when it doesn't start, it doesn't do anything else either - what I mean to say is - its not like its hesitating or trying to start - just doesn't do anything (except the cranking noise of course). Could it be a fuel flow problem - leaky fuel line, or leaky fuel pump (the fuel pump should come on when I switch the ignition on, right? its not linked to starting the car)? I plan to take it to my mechanic this monday again, but want to get as much "headstart" before that as possible, because otherwise, it becomes a wild goose chase.

Another questions - do you think the two problems (cold starting, rough cold running) are linked at all?

Also, this is for Steve, what is the differential pressure you were talking about - for diagnostics? I want to understand it before I can ask my tech to do it.

Again, thanks a bunch to everyone who's helping me out.

Rags.
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  #7  
Old 07-27-2001, 03:22 PM
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Its a big subject as one thing leads to another. It goes to the basic design function of KE-Jetronic. I'll try for the short story version.

You first started with K-jet and it was totally hydraulic. The only electrical part was the fuel pump. Its metering was strictly pressure related. The K-jet with lambda was the first attempt to modify mixture to suit an electronic calculation. It involved an external valve that pulsed and leaked away the lower chamber fuel pressure. It worked on top of the hydraulic mixture controls.

The KE put the valve right on the side of the fuel distributor and replaced all but the basic airflow balance with electronic pressure control on the lower chamber. By having the lower chamber pressure less the diaphram allows more fuel to flow. Ther is a critical balnce of orifaces and leaks that allows the differential pressure to be controlled from zero to about 7psi. Each increase in EHA current (see my article about driveability diagnosis in the DIY section) results in a larger pressure drop.

One will be looking for total system pressure, base differential pressure, electronic current control for starting enrichmnet, cold enrichment, and differential pressure differences to correspond to the current actuations.

But don't forget to check ignition. Secondary output voltage, rotor grounding, etc.

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  #8  
Old 07-27-2001, 11:19 PM
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I think that the cold start valve is controlled by the fuel pump relay on this engine. I would check this and replace that relay if needed. This will help cold starts. I have read that on the 300e's, Mercedes updated the controll points of the fuel pump relay.
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