fuel tank pump

[Glendonwyn]

C270cdi Can anyone tell what the fuel pump in the tank is for? and when it is meant to operate? and also how to check if it is working correctly? Trying to sort out a P1187 code problem.

 

[BlackC55]

It operates all the time the car is running or being cranked. To c heck if its working properly you need to check the fuel pressure with a gauge.

 

[Glendonwyn]

Thank you,
I have checked the pump relay and can here it switching on at cranking and off when the ignition switched off.
I removed the 20 amp fuse for the pump relay while the car was running and also before starting the car and no effect, car still started and run ok, although I still have engine shut down under hard acceleration, code P1187 common rail pressure variation.

Someone has fitted a check valve in the fuel line, just before the fuel filter at the engine, possibly because the tank pump wasn't priming the mechanical lift pump and they would have difficulty starting.

I will now check wiring to the pump.

Last question(I hope), Should I be able to hear the pump with the back seat lifted and the access panel removed, or is it really quiet?

Need to be right before ordering the part as it's £253!

 

[BlackC55]

Before you do anything else. Get it on a Star.

 

[E270 Owner]

You have a faulty injector.

As a matter of course use MB Star to test the fuel system and leak off test.