I've had my 1991 300CE, 138m for almost 4 years now. The start has never been perfect, always a pause, a stumble and then the engine finally catching. Once in awhile after a cool evening I would get an instant first start in the morning with the engine revving higher to warm up the car. This must be the cold start valve working correctly? Hot starts ( after 5 minutes or so) are also good instant starts. But the rest of the time it is pause, stumble and finally catching. Recently now the pause is even longer before the engine finally catches. If it doesn't start and then I immediately try again, then it starts a little quicker with the same stumble. It seems fuel starved on start up. Otherwise the car runs and idles perfectly.

Where should I start and what items should I check?

Thanks,

glenmore
1991 300CE
2000 C280
1990 LS400

fuel distributor issue maybe?

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1994|040|W124.036|E500
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Test your Coolant Teps sensor. I'll bet you have one out or just on the edge. Start there

Could be fuel accumulator valve. The function of this check valve is to maintain fuel pressure after shutdown. Is it worse in the morning at first start up?

The valve is located back with the fuel pumps. Costs about $90. Easy to replace.

My symptoms were that on overnight startup I had to let it crank until the fuel pressure built up enough for the engine to start. Since the valve had a slow leak, start ups after short shutdowns displayed less of the fuel starvation syndrome.

Steve

Actually the start up in the morning is usually a little better as the cold start valve sometimes kicks in. Here in SoCal it is never very cold overnight so I can't really tell if it should always kick in or not. Hope it is not the distributor or the accumulator. They are both big $$$.

Coolant temp sensor and check valve it is then!

glenmoe
1991 300CE
2000 C280
1990 LS400