Hi All, I'm new here. Just finished 2014 ML350 Oil cooler project... and Black Death restoration. Also, Swirl flap delete with flaps fastened in open position... 4.k ohm 1/4 watt resistor. Massive dirty job. Got the car started and it ran for about 5 minutes and quit.

After the engine quit... code 254000 (Stored) The signal for the pressure sensor of the low-pressure fuel circuit is implausible. Also, code 008700 (Active and Stored) The fuel pressure in the system is too low.
With the live feature of my code reader, low pressure fuel pump in the tank shows only 1.2-1.4 BAR while cranking. HERE IS THE MYSTERY. Pour in a couple of liters of diesel in the tank, ... crank and it starts!

I think the fuel pump, however, worked fine until I did the job. Could it be a faulty pressure sensor somewhere in the front engine compartment? I don't want to drop the tank and replace the pump. (Lots of work and expensive)

What is bizarre is that dumping fuel in tank restores pressure. HELP!

Also, if anyone could tell me how to delete a thread, I posted this 2x in the wrong forum sections. ;.). Thanks

 

After getting back down to the injectors on the OM642, I found a considerable leak coming from the fuel supply pipe off of the high-pressure rail. Gave it a good crank... no leak.

Car starts again, no codes of low-pressure fuel issue. Wonder why it took throwing fuel in the tank to get the low-pressure fuel pump to running pressure. Just weird.

 

Gravity.

 

yes.

I was going to update this tonight. Same issue happened… started throwing more codes related to low and high pressure…. Started limping. Low fuel pressure again from the low pressure pump in the tank. It appears that the pump is weak. Filling past 1/4 tank allows the car to run again and the pump hits 4.5 BAR. If below 1/4 the pump will only hit 1.25 BAR even on crank. Dumped 20 litres in … runs like a top.

I will be replacing the pump in a few weeks… for now, I will make sure not to go below half a tank and let “GRAVITY” do its work.

Cheers.