Changing fuel filter -- 1987 300DT - PeachParts Mercedes-Benz Forum

Jeremy5848 · #1 01-23-2007, 12:38 PM

I want to change the fuel filters on our new-to-us 1987 300D Turbo (W124) car. Well, it's an easy procedure on the 123 but the secondary filter on this 124 is wedged between a whole bunch of fuel lines at the rear and the vacuum line and radiator hose at the front. It looks like one must unbolt the bracket holding the filter and lift the whole assembly up to get the filter loose. The FSM says "withdraw downwards" but the PS pump bracket is there. What do you more experienced operators do?

Hit Man X · #2 01-23-2007, 01:01 PM

I just move that vac line to the booster out of the way. It's not as difficult as you think.

justinperkins · #3 01-23-2007, 01:03 PM

Pull the primary vacuum line out of it's bracket and push it out of the way, then you can pull the filter out towards the front of the car. You'll have to smoosh the upper radiator hose but if you've got a good hose it shouldn't be a problem.

I recommend putting some towels down over the S-belt because you will absolutely spill some fuel trying to force that thing out of there.

Before you screw the new one in, you'll want to top it off with CLEAN fuel (use some diesel purge or some other additive), but do that after you've mostly wedged the filter in place to avoid more spillage.

Jeremy5848 · #4 01-23-2007, 01:16 PM

Thanks, guys, I'll give it a try.

gsxr · #5 01-23-2007, 01:56 PM

More specifically, unscrew the main plastic vacuum line from the vacuum pump, and pull it out of the metal bracket. I don't unbolt the bracket though. It comes forward and then upward. Remove the center bolt, don't forget to replace both O-rings. If you don't fill the new filter with clean diesel (or better yet, Diesel Purge)... you'll be sorry. (Don't ask how I know this!)

airbus · #6 01-23-2007, 02:18 PM

Quote:

Originally Posted by gsxr

More specifically, unscrew the main plastic vacuum line from the vacuum pump, and pull it out of the metal bracket. I don't unbolt the bracket though. It comes forward and then upward. Remove the center bolt, don't forget to replace both O-rings. If you don't fill the new filter with clean diesel (or better yet, Diesel Purge)... you'll be sorry. (Don't ask how I know this!)

How do you know this?

justinperkins · #7 01-23-2007, 02:27 PM

Quote:

Originally Posted by gsxr

More specifically, unscrew the main plastic vacuum line from the vacuum pump, and pull it out of the metal bracket. I don't unbolt the bracket though. It comes forward and then upward. Remove the center bolt, don't forget to replace both O-rings. If you don't fill the new filter with clean diesel (or better yet, Diesel Purge)... you'll be sorry. (Don't ask how I know this!)

I never messed with unscrewing the vacuum line from the pump and instead opted to unbolt the bracket. I was nervous about breaking some seal that the vacuum line had to the pump or something, probably just being paranoid.

gsxr · #8 01-23-2007, 02:53 PM

For future reference: There's no seal between the line and the pump, it a metal-to-metal compression fitting.

justinperkins · #9 01-23-2007, 04:12 PM

Quote:

Originally Posted by gsxr

For future reference: There's no seal between the line and the pump, it a metal-to-metal compression fitting.

Now I know, and knowing is half the battle.

Hit Man X · #10 01-23-2007, 05:44 PM

Quote:

Originally Posted by justinperkins

Now I know, and knowing is half the battle.

badtrukrisin · #11 01-23-2007, 06:14 PM

When I change my filter I move it a little forward and suck out the diesel in the filter and put it in a can and when I replace the filter I fill it up with Diesel Kleen(or Diesel Purge if you have it) and screw the bolt back in. Saves a lot of mess for me.

Bud

Jeremy5848 · #12 01-23-2007, 06:30 PM

I put fuel in the new filter -- it was easier to get the filter in place dry, wedge it up with a piece of wood, and then add the fuel through the center hole with a funnel. Then I inserted the bolt and tightened everything up. The engine started but then stalled and now won't start. The primary filter is full of fuel; I thought the secondary was self-purging -- at least that's what the FSM said? I'll put more fuel in the secondary and try again.

justinperkins · #13 01-23-2007, 07:13 PM

Quote:

Originally Posted by Jeremy5848

I put fuel in the new filter -- it was easier to get the filter in place dry, wedge it up with a piece of wood, and then add the fuel through the center hole with a funnel. Then I inserted the bolt and tightened everything up. The engine started but then stalled and now won't start. The primary filter is full of fuel; I thought the secondary was self-purging -- at least that's what the FSM said? I'll put more fuel in the secondary and try again.

You need to crank it for a while. Crank it for 15-25 seconds, let the starter cool for 30 seconds or so, then try again. Repeat until it starts.

Excellent idea badtrukrisin, wish I'd thought of that sooner

Hell yeah Hitman, I was a GI Joe freak as a kid.

Jeremy5848 · #14 01-23-2007, 08:26 PM

Yeah, it just took awhile. At least I have a strong battery, although I did put a charger on it between attempts.

I checked, the secondary filter was full of fuel. I guess the air that got into the system must have blocked the IP. Thanks for the help and encouragement, everyone.

greasybenz · #15 01-23-2007, 10:34 PM

Next time after you turn on the engine push the pedal to the floor immediately.
That way the IP is responding by sending more fuel and that way youll quickly get all the air out of the system and fill up the fuel filter properly.

Works for me everytime.