Need some help on cold start problem (continuation)

The cold start valve should operate for only a very brief period - seconds - depending on the engine's temperature [colder = longer].

I suggest you get the specification voltage for the cold start valve - I don't know it, but 2 or 3 volts strikes me as very low.

I'd focus on the thermo-time relay.

Ok, I bought and installed the thermo time relay, at least I think that's what I bought. I think it's the temperature sensor for the fuel injection system. (picture:

I'm having a small problem with it. There's four pins and no directional notch, so you can plug this thing in any of four ways! Although the plug that plugs in on top of the sensor has the pins numbered, the original sensor has no numbering what-so-ever. The new sensor has a number 2 stamped on one side but it's exactly in between two pins, so you don't know which one's number 2? How in the hell do you know which way this is suppose to plug in?

Now what I did was remove the connection from the cold start valve and put a volt meter on it, pluged the thermo sensor it and read the voltage when I was cranking it. No mater which of the four ways I plugged the sensor in it always reads 2-3 volts at the cold start valve. The position of the plug has no effect on the output to the cold start valve. Which leads me to believe that the temperature sensor I bought has nothing to do with it.

Did I buy the right sensor? What is the correct position the sensor I bought is suppose to be plugged in?

T.G. Lambach wrote:

Whereabouts is that sensor located? I've very recently bought a 190e which has had the cold start sensor unplugged due to otherwise being constantly on. I've bought a service manual on CD which is of very limited worth to me as it only covers US models and is LHD specific. I'm suspecting the ambient temperature sensor is faulty but i wish i knew where they hide it. Mine is a 1989 2.0l model and i'd like to fix it before winter strikes in another month or so and we nearly get cold enough for a frost.

To view the day to day life of a loser go here.

Gents,

There are two temperature sensors. The CIS water temp. sensor $39, $34 street, is on the intake manifold and the engine temp sensor (3 pole) $42, $36 street, is probably on or near the engine's thermostat housing.

Back to the initial problem.

Looking at the model's repair parts I don't see a thermo-time relay so the temperature sensor you bought is the only one I see related to the fuel injection.

As a test, I suggest you temporarily remove and plug the EGR's vacuum line for a cold start to test the 70 degree thermo-vacuum switch, if only to exclude the EGR from the possibilities.

The engine's various fuel injection parts are quite expensive so I suggest you read about CIS fuel injection to learn its theory before proceeding, otherwise this could be a very expensive education.

When I called the parts house and asked for a "thermo-time relay" they had no idea what I was talking about. I said it's part of the cold start system and probably what feeds the cold start valve. The part in the picture is the part they sold me.

I thought by doing it myself with some help online I could save myself some money. So far I'm spending more in parts on a wild goose chase than I would to have the initial diagnosis.

Thanks for your help on the matter, but I think it's time to take it to the shop.

Thanks again.

T.G. Lambach wrote:

I've just found the part in question on my car. I'm thoroughly convinced now that mercedes don't want mere mortals to know anything about them. A four prong plug that can be connected in four different ways. Devious and brilliant.

To view the day to day life of a loser go here.

One last thing...

I just had somthing happen. I was starting it cold and it was doing it's usual thing sputtering up to where I could get it to idle while holding my foot on the gas... and then somthing "clicked" under the hood and the idle smoothed out and shot up to about 1000 RPM, like it's suppose to be. I think at that exact moment the Check engine light flashed on then went off. The "click" sounded like it came from the passenger side of the engine compartment.

Any ideas what this could be?

Some cars, and I don't know about your model, have an "overvoltage protection relay" which causes strange things to occur when it malfunctions. Others will be able to give you more information about it, including means of identification. I believe it has a fuse on its top. Suggest you start a new subject on NG: "Overload Protection Relay?" to draw fresh interest.

Bingo.

I did some more research and found out the overvoltage relay is a common problem with my symptoms. The untechnical way to check it is take the relay out (located behind a plastic cover behind the battery) and lightly shake it. If you hear stuff shaking around in there it's probably bad. In my case I heard somthing moving, but it was a uniform sound every time. So I suspected it wasn't broken. I also heard you can give it a couple light taps to solve problems with it.

I did all this and put it back in. Turned the key and the car started instantly while cold and held a 700 or so RPM.

So that was it. It's either > Some cars, and I don't know about your model, have an "overvoltage

Good! I'm glad you solved the cold start problem, albeit with a detour to the cold start valve.

Suggest you ask about, but not buy, the fuel pump relay - location etc. for relays get tired and become intermittent. In the case of the fuel pump relay the engine stops - but then will usually immediately restart. Eventually it becomes too intermittent and the restarting becomes less instant.

Enjoy your "new" car.

Yes, I'm a happy Mercedes owner again. :)

I just picked up some newer OEM wheels for it. I think it makes the car look more modern. Here's some old (stock wheels) and new (newer wheels) pics to share with the group...

T.G. Lambach wrote:

Nice car, similar color to my Smoke Silver E320 - great color, doesn't show the dust etc.

Enjoy.