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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Qualified Mercedes Benz Diagnostic Technician - 20+ years experience - Workshop Foreman for Mercedes
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Mercedes: 220cdi(202)gives a dtc error code p1187 and the car

Resolved Question: mercedes 220cdi(202)gives a dtc error code p1187 and the car sometimes doenst start and wen starts a drive and we stops and is dificult to start again.tanks
Submitted: 7 years ago.
Category: Mercedes
Expert:  MB Paul replied 7 years ago.

Code P1187 relates to the rail pressure & can be caused by many different things.

The first & most common problem is air being drawn into the low pressure lines - check for any signs of fuel leaks around the engine. Often no fuel will be visible but air can still be drawn in - check for signs of air in the low pressure lines from the filter to the fuel pumps & upto the rail. If air is present then I would replace the O rings at the end of the low pressure lines.

I have had problems with non genuine filters so if the new one was a pattern part I would replace with a genuine part.

The injectors can also cause problems - when these wear they flow too much fuel back down the return line, this reduces rail pressure causing non start and/or cutting out. Special measuring tubes are required to test these.

At the rear end of the rail there is a valve - the seals on the end of this valve can leak internally also reducing rail pressure - care must be taken when removing this as the end is fragile & can break off inside the rail!

The pump is a possibility, again a special tool is required to test this - it is unusual to fail in this way but is a possibility. Usually it either works or does not.

If it has happened suddenly then poor fuel is another possibility, again unusual but I have experienced this.

Best regards, Paul
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