Yet another new member with a starting problem - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 08-30-2008, 02:40 PM Thread Starter
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Date registered: Aug 2008
Vehicle: 1990 230TE
Location: Co. Kerry
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Yet another new member with a starting problem

Hi all,

I have a 1990 230TE (w124 of course) which has been great to drive and makes me wish I'd gone for an old Merc a long time ago - ah well. Of course there's a fly in the ointment - cold start problems lots and lots of turning over before a shaky hesitant start that then needs to be held at 2000 rpm for a few minutes before it will idle. I've been digging into them with a lot of help from postings at benzworld. I know the cold start valve is working and is getting power (so I guess that means the thermo time switch is OK - where is it BTW), I know the airflow sensor is fine, I've had the OVP relay apart and looked at the soldering - all this seems to be fine. There seems to be a decent spark. Loosening the inlet or return from the fuel distributor produces a great spray of petrol, but the only place it comes out is the cold start valve, the feeds to the injectors only produce drops not squirts. Once running and warmed up all seems to be fine apart from the occasional cough especially when returning to idle.

She used to start to a touch and I feel sure there isn't really much wrong but I'm not at all sure where to look next.
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post #2 of 3 (permalink) Old 09-01-2008, 04:59 PM
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Date registered: Sep 2006
Vehicle: 1993 400E, 1997 E420, 2003 E500
Location: OH
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I'm having similar problems. My CSV is only spraying for 1 sec or so when I have it pulled from the engine and crank with the CSV connected and electrical connector attached. When I have the CSV disconnected and crank, the line fills the cup with gas in a second. Not sure if it's my CSV or thermo time switch and not sure where this switch is. Yours CSV may either not be working or may not be cutting off after the 5-12 seconds it should function. I ran across this and it seems correct, I'm sure someone will let us know if not:

The cold start injector receives battery voltage whenever the starter is engaged and is grounded through a device known as a thermo-time switch. The thermo-time switch is a temperature sensitive bimetal switch designed to provide a ground for the cold start injector when the temperature of the engine is less than 95 degrees F. A second circuit in the switch is an electric heating element intended to heat the bimetal as the engine is being cranked.

Consequently, the cold start injector should operate only when the engine is being cranked, the temperature of the engine is less than 95 degrees F and for a maximum of five to twelve seconds.

Two of the most common symptoms of a cold start injector problem are hard starting when cold becuse the cold start valve is not operating and a leaking cold start injector which can cause an extremely rich running condition.


The injectors are working continously. They spray fuel on the outer side of the intake valves.

During cranking the injector line is closed because there is no vacuum behind the thottle.

During start (with normal temperature at engine) fuel is supplied for ~10 sec via the start valve.

With very cold engine the injector line is opened by the cold start idling regulator by vaccum too.

The normal supply needs running engine, vacuum build up in the intake manifold and a floating air flow sensor plate in the air stream at the top of the fuel distributor to regulate the air/fuel mix.

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post #3 of 3 (permalink) Old 09-03-2008, 08:40 AM Thread Starter
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Date registered: Aug 2008
Vehicle: 1990 230TE
Location: Co. Kerry
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Interesting. I haven't tried to find out how long my CSV is staying open for, until recently it wouldn't have mattered if it was less than a second since the engine was starting on the first revolution.

I may have found my real problem - there seems to be water getting into the fuel. When I finally got it started it was running lumpily and there was water in the exhaust, dripping from a hole I didn't know about (something else to fix). I suspect the charcoal canister. I'll find out at the weekend.

One thing seems well worth noting - if you're right tgordy41 then if the engine doesn't start within 5 seconds of cranking then it's best leave it for a bit (anyone any idea how long the thermo time switch will take to cool from electrical heating only ???) before continuing cranking.

I believe (someone please confirm) that the thermo time switch is the unit screwed in at an angle below the temperature gauge sender which in turn is just in front of the temperature sensor used by the KE-jetronic system.
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