My 190E 2.3 will not cold start

The fuel pump on my car will not consistently turn on in cold weather. How can I be certain its the fuel pump relay or the engine temperature or what?

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There's the electric pump, its relay and the possibility of ice in the fuel line or dirt and ice in the fuel filter. That's the choice IF there's no fuel to the engine.
Of course, there's also the engine's cold start system which adds some fuel to the intake specifically to get the motor started.
So how does one find out which of these possibilities is the culprit?
If it were my car, I'd loosen, not open, the fuel line to the engine and briefly crank it with the starter. If there's a significant fuel leak then there's fuel TO the engine and the cold start system ought to be checked. But if there's no fuel leak then the fuel pump, fuel pump relay or ice in the fuel line are the choices. If you hear the electric pump run very briefly when switching the key ON then it's probably OK, if not, the pump or its relay are suspect. If you do hear the pump but there's no fuel you must consider the possibility of ice in the fuel line and / or dirt and ice in the fuel filter.
Others here can tell you how to "jump" the relay to test the relay and pump.
The cold start system varies somewhat by engine. Basically there's a temperature sensor, a time-temperature relay and an electric fuel valve on the intake manifold. The cold start system won't work if any of the three is defective or disconnected.
Hope this helps you get it running.
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Hi there, I am not merchanic.I got the same problem with my car.If I keep on clanking the engine for about 1/2 min,it will start!Try and see if this work!if this work,that means you have leaking fuel!To check fuel pump relay,put your hand on the relay to feel,have some one put the key in to the ignition,turn on but do not start! If you could feel a sound or a little noise that mean the fuel relay is working. Or bend down to the the pump listen and see if you could hear a big air sound when the person turn the ignition on!That means fuel relay is working! Quang
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