Help diagnosing cold start problem (93 190E 2.6)

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Warren Bell - 23 Mar 2005 17:06 GMT

I just bought a Mercedes 190E 2.6. In the mornings when it's cold it
takes a few minutes of cranking and playing with the gas before it will
finally sputter and kick up to where it will idle.

What I have to do to start it is crank the engine and slightly tap the
gas. Once it kicks like it's going to start I have to immediatly let
off the gas. Then it will accelerate a little more. If I keep my foot
off the gas it will die out, so I have to lightly hit the gas again and
then let off again. Keep in mind that it accelerates when I'm letting
off the gas. It's like it's killing the engine when I push down on the
gas and accelerating when I let off. But I need to push on the gas to
give the engine some fuel.

So I need to pump-release-pump-release to get it going. After it warms
up a little it runs fine, and once it's warm it starts fine.

Does anyone know what could be causing this problem?

Thanks.

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T.G. Lambach - 23 Mar 2005 18:36 GMT

The cold start system needs to be repaired. The engine isn't receiving
adequate fuel for its cold condition, more fuel is needed. When you open
the throttle the air / fuel mix gets even leaner so it stumbles even more.

This won't fix itself so find an independent M-B shop and have them
repair it. Ask for an estimate before saying "fix it".

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Tiger - 23 Mar 2005 19:19 GMT

Basically your "choke" or warm up is not working... It can be as simple as a
temperature sensor for fuel injection system... because everything depends
on this sensor to tell the computer the temperature of the engine;

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Administrator - 24 Mar 2005 00:23 GMT

Thanks to everyone that replied.

Now what I would like to do is do a little troubleshooting myself. I
grew up working on all my cars so I'm fairly machanically inclined...
but I haven't worked on anything in many years and never on a Mercedes.

Anyway... I did a little research before posting and read somewhere that
you can test the cold start valve itself with a switch and a nine volt
battery. Somthing about wiring it up to the valve with a switch to
break the connection from the battery. Crank the car and hit the
switch. If it starts normally, then the cold start valve is
functioning. From there start looking down the line more. If it
doesn't start normally, then it's likely that the valve is bad.

Does this sound right? If I should try this, where is the cold start
valve located? And lastly, if the car does start fine, meaning the the
valve is operating properly, what should I look at next as a possible
culprit?

Thanks!

> The cold start system needs to be repaired. The engine isn't receiving
> adequate fuel for its cold condition, more fuel is needed. When you open
> the throttle the air / fuel mix gets even leaner so it stumbles even more.
>
> This won't fix itself so find an independent M-B shop and have them
> repair it. Ask for an estimate before saying "fix it".

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T.G. Lambach - 24 Mar 2005 02:33 GMT

An enterprising new owner!

Well, the cold start system has basically, as you've learned, an
electric cold start valve, a temperature sensor and a time-temperature
relay. You already know about the clod start valve so there's no more to
say about it. Rather than powering the valve I'd put a voltmeter on its
lead to see if it receives power during cranking. It probably doesn't.
That leads back to the thermo-time relay which powers the cold start
valve for shorter or longer periods, depending on the engine's
temperature. We're talking seconds, not minutes.
Finally, there's a temperature switch, ON below XX degrees, OFF above that.

These three parts are in a chain, failure of one kills the whole cold
start system so your task is to diagnose which is defective and replace
it. My $$ would be on the thermo-time relay.

Hope you solve the problem.

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wjbell - 24 Mar 2005 07:39 GMT

Ok, thanks for the info!

I'll post back to this thread with the results.

> An enterprising new owner!
>
[quoted text clipped - 13 lines]
>
> Hope you solve the problem.

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