It starts................eventually

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bluefish

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I've got a 1984 190e 2.0lte and it's always had a problem starting. It will take up to 10 attempts to get it going - sometime I've had to jump start it 'cos the battery hs gone flat through trying to start it. It's not so bad in the summer but winter means I just park it up and get the bus!!

Once it does turn over and fire I have to wait 5-10 minutes for it to warm up otherwise as soon as I press the accelerator it cuts out - not very safe if you get going and need to pull away from a juction.

Any Ideas
 
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flyingtech55

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Hi Bluefish

What you have to remember with these engines is that the injection system is basically mechanical...the old Bosch K system. Once its started and up to temperature, the engine will run satisfactorily on the mechanical part of the system alone as your appears to.

The electronic part basically has three functions-

1) A 'choke' fuction to enable the engine to start.

2) A mixture enhancement function during warm up.

3) Once the warm up cycle is completed, a mixture 'trimming' function during running to control emissions.

The system works as follows-

1) When engine cranking commences the cranking feed activates, via a thermo-switch, a fifth injector. This injects extra petrol for a predetermined period to enable a cold engine to be started then shuts off. This system is what's known as a dumb system. (ie no feedback) and is akin to using full choke to start a 1970's carburettor engined car.

2) Once the engine starts, mixture enhancement is used until the engine warms up. The degree of enhancement is steadily reduced during the warm up cycle using feedback from the engine temperature sensor. This is an intelligent (servo) system. This is akin to gradually pushing in the choke as the engine warmed up on the 1970's car.

3) Once the engine is up to temperature, mixture enhancement stops and the electronic system starts to use the output from the Lamda sensor (if fitted) to monitor the mixture. This is the method used to control the emissions. This is also an intelligent (servo) system.

This is a bit of a simplification as there is also a throttle position sensor which is used to cut the fuelling on the overrun above certain speeds and provide mixture enhancement under acceleration to eliminate flat spots and so on.

However, you can see where this is going. Your car is very difficult to start then runs like a dog until it warms up. I would say that it is running on the mechanical part of the system only. In theory it shouldn't start at all but the injectors are probably a bit worn and allow just sufficient petrol into the cylinders to eventually get the thing to start if the day isn't too cold. No chance in the winter!

Proceed as follows-

Remove the air filter assembly and ensure that the two pin plug is plugged into the fuel regulator (near the base at the front). If that's OK, on the bulkhead near the battery there is a small unit with a fuse on the top. This is the main system fuse. Check its not blown. On later ones I don't think the fuse is visible. This may well be the over voltage relay that I've heard people talking about. Thirdly, the famous (infamous) fuel pump relay. This is obviously working OK fuel pump wise because the engine runs once its going but it does a lot more than just run the pump...it does other switching too. Finally, renew the temperature sensor because if it goes out of tolerance it can cause some odd symptoms.

Renewing the temp. sensor, checking the main system fuse and checking the two pin plug are the quickest and easiest things the start with (no pun intended) then check the relays by substitution.

Don't be afraid of the injection system because it is very straightforward and not difficult to repair if you proceed logically. Hope all this helps.
 
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squirrell

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bluefish said:
I've got a 1984 190e 2.0lte and it's always had a problem starting. It will take up to 10 attempts to get it going - sometime I've had to jump start it 'cos the battery hs gone flat through trying to start it. It's not so bad in the summer but winter means I just park it up and get the bus!!

Once it does turn over and fire I have to wait 5-10 minutes for it to warm up otherwise as soon as I press the accelerator it cuts out - not very safe if you get going and need to pull away from a juction.

Any Ideas
Click to expand...

Check the over voltage fuse (located on top of the silver reley behind the battery), this is common as jump starting these vehicles causes it to blow.
sounds like CISE has no inrichment.
 
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teky

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haynes heheheheh dont think so m8 its from my autodata books, im a member of the w123 site and have often given this kind of data, i bought the books for my buisness "very expensive" now im in early retirement i use the books to help others.

got to invest in a spell checker :oops:
 
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number_11

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Check you over voltage protection relay for a blown fuse, if the fuse is ok then check for an output from the relay. The relay itself may be faulty. These relays have been modified many times over the years. The latest has on fuse on the top, sideways on.
 
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c4791p

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1992 300SL Hard Starting

:( It has now been four weeks I've been fighting a severe hard starting problem. We've only had the SL since Jan 03 and other that having to crank the car for 8-9 seconds or so, it started fine. Well, took it to the local MBZ shop that's worked on my cars before for the 140K mile service and mentioned that it was getting harder to start and we smelled fuel when it finally started.

Since we've had it back (4 weeks) it is a real devil to start. If this were the old days, I'd say that something screwed up in the cold start circuit. Rember the carburetor days when you would depress the gas pedal clear to the floor and the butterfly valve on the carb would be held open until the engine warmed, well now to even have a prayer of starting we have to turn on the key, depress the gas pedal clear to the floor twice and then crank the engine.

It still may take two attempts and its really embarrasing in a parking lot.

Once the car starts, it runs flawlessly.

Help!!

Chuck Parker, Las Vegas, NV usa
 
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