Diesel purge attempt and OM616 fuel filter change

Since I purchased my 240D, I had planned to use ‘Diesel Purge’ to clean the injectors and injection pump.   The car runs well, but it is a bit rough at idle and I figured this would probably help.

This was part of my plan to clean the fuel system for the entire car.   I have a suspicion that the strainer in the bottom of the fuel tank is somewhat clogged up.    To change that, I am going to wait until the amount of fuel in the tank is far lower.   I don’t really want to be dealing with 60 liters of diesel.   Given the excellent fuel consumption of the 240D, it will take some time before the tank is down to about a quarter.

In the meantime, today’s job was to use the diesel purge and then change the pre-filter and main fuel filter in the engine bay.   I figured this would be a simple job.     Turns out I was optimistic.

I transferred the diesel purge into a clear container that I could use to run it through the fuel system.    This is my first diesel, so there is probably a level of rookie error, but I simply could not get the engine to prime with the hand primer pump.   Mostly it was very hard to get the air bubbles out of the lines.   The primer pump would not really pull very much fluid ‘up’ a line.   if I kept the fuel line as flat as possible, it would pull fuel along, but not fully prime it.

I don’t know if my issue was rookie error, or that my hand primer pump does not work very well.   Most of the information I could find on the internet refers to them leaking when they fail, and mine does not leak.

I persevered for a couple of hours and could not get the engine to start.   Since by this time it was about 10:30pm, I moved to plan B.    Instead of worrying about the diesel purge, I changed the pre-filter and main filter and connected the fuel tank back up.

I was keen to do this for a few reasons.   Firstly, if the strainer is a bit clogged up, chances are these filters are too.    Secondly, the factory pre-filter is clear, which allows an easy check to see if it is becoming clogged up.   My car had an opaque aftermarket filter.

It took me over an hour to finally prime the fuel system and start the car.   There were many attempts, as well as some time to charge the battery up a little to allow me to try again.   During one of the times I was waiting for the battery to charge a little, I cracked open the plastic pre-filter with a pair of channel locks.   it was pretty dirty inside.   I also tried to look inside the main filter and it looked pretty dirty too.

At this point I don’t know the condition of the strainer, but seeing the condition of the pre-filter confirms my intention to change it.   It must be pretty clogged up for that amount of debris to get through it and into the pre-filter.

Since I had a litre of diesel purge in an open container, I just poured it into the fuel tank.   It might not provide a concentrated clean there, but I’m sure it will help at least somewhat.   I’m still not sure why I wasn’t able to prime the system properly.   I’ll have to look more into that.