Changing CDI Fuel Filter - PeachParts Mercedes-Benz Forum

shertex · #1 10-03-2015, 06:07 AM

The recommended interval for the fuel filter on the CDI is every 26k miles. However, what I've typically done with the W124 and W210 is simply wait till the car feels sluggish. It's usually pretty obvious and sudden. If it's been a while and I'm about to go on a long trip, I may change it just to be safe.

Is there any reason not to adopt this policy with the CDI? It's a different configuration: just one filter instead of a main and pre. So I was wondering if there's any downside to a longer interval.

engatwork · #2 10-03-2015, 07:21 AM

Do what Mercedes says to do. Different creature with the high pressure pump and direct injection injectors. You don't ever want to have to purchase any of the parts associated with the fueling $system if you can help it.

jcyuhn · #3 10-03-2015, 08:43 AM

On the w211 om642 bluetec they specified 20k miles. It's effectively every other oil service, same as your number. I believe this was later revised to 40k - every 4th service. The fuel filter is also the water separator. I think this is why they were so conservative on the change interval.

Does the om648 filter have a water sensor that is swapped to the new filter? That thing has always given me fits on the bluetec, it likes to leak. The new filter comes with fresh o-rings for the water sensor. I put in a Hengst this past summer. The o-rings just failed, it was literally spraying diesel under the hood. I replaced them with a couple of fuel system rated o-rings from the local parts store and all is good. The Hengst rings look like they were not rated for fuel system use, they appear eaten away and are hard rather than pliable. Never had this kind of inconvenience on the older cars.

GregMN · #4 10-03-2015, 08:45 AM

Change the fuel filter filter every other oil change. This is a completely different fuel system than 60x and 61x motors.

pmckechnie · #5 10-03-2015, 10:04 AM

My opinion on fuel filters. Take it for what it is worth, not much. I try to change my filters every year unless I have performance issues. Filters are put there to catch trash that gets in the tank from dirty fuel. If you always get clean fuel you don't need to change the filter. If you get dirty fuel the day after you change the filter, then you will have to change it again.
The engine will tell you when to change the filter.

PaullM

MTUpower · #6 10-03-2015, 10:48 AM

^^^^^^^^^^^^^^^^^^
Fuel gets "dirty" by itself in the fuel tank. If your tank is less than full then there is air in the tank. The temp change from day to night causes water to condense in the tank- if the tank is near empty over a long time period then you may have lots of water condensing. This water forms a water/fuel surface where growth of microbes can and does occur.

Diesel911 · #7 10-03-2015, 11:14 AM

Quote:

Originally Posted by shertex

The recommended interval for the fuel filter on the CDI is every 26k miles. However, what I've typically done with the W124 and W210 is simply wait till the car feels sluggish. It's usually pretty obvious and sudden. If it's been a while and I'm about to go on a long trip, I may change it just to be safe.

Is there any reason not to adopt this policy with the CDI? It's a different configuration: just one filter instead of a main and pre. So I was wondering if there's any downside to a longer interval.

In general with Filters as they plug up they Filter better closer to the end.

Does that damage or shorten the life of something else? I can only say it does not seem to damge anything on other Filtered equipment.

The main issue with letting the Filter go till performance drops is you could end up on the side of the Road and maybe in bad weather changing the Filter.

If the Filter is expensive perhaps another cheaper Flter could ge added to the system.

I also wait till my Car has performance issues or somthing like 5 years has passed.

shertex · #8 10-03-2015, 11:20 AM

Hmmm....I was going to buy a Hengst. Maybe I should splurge and buy MB branded?

shertex · #9 10-03-2015, 02:09 PM

Do I need to fill the new filter with diesel before installing? Can I use ATF, or is that too "old school" for the OM648?

Skid Row Joe · #10 10-03-2015, 02:42 PM

BOOKMARK THREAD

engatwork · #11 10-03-2015, 03:40 PM

I always fill it with diesel fuel.

jcyuhn · #12 10-03-2015, 04:34 PM

No need to fill it. Just turn the key to the "run" position, wait 30 seconds, and then start the car. The electric lift pump will fill the filter. Car will start and run without the slightest hiccup.

If mb used the newer clic type hose clamps, be sure to use the same type. Screw type clamps will eventually leak. A reasonable set of clic pliers can be had for twenty bucks from Amazon.

shertex · #13 10-03-2015, 05:03 PM

I think PO has screw type clamps on there...shall I convert to clic?

jay_bob · #14 10-03-2015, 09:42 PM

Yes you should definitely use the proper Oetiker clamps and OE filter.

The car has an electrical fuel delivery pump, you do not need to pre-fill like you do on IDI engines. Switch on and wait 20-30 seconds and you will be good to start.

This is tracked on my W164's maintenance tracker system as Job 11, be sure to reset this in the service menu.

shertex · #15 10-08-2015, 07:00 AM

Interestingly, the dealer where I get all my MB branded parts (Gainesville, FL) use screw clamps....techs said the prefer over clic.