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Current 2017 GLE350, 2007 S550, 2002 S430, 1998 ML320 Deceased 74 240D, 92 400E, 97 E420, 13 GLK350
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1,915 Posts
Discussion Starter #1 (Edited)
I replaced my fuel filter my 2002 S430 with 64k miles for under $50. This was done near the recommended schedule time of 60k to help ensure a smooth running engine. One fourm post indicated a dealership charging $200 for this job. This is a medium difficulty DIY job, requiring you to jack up the car, work on your back, and handle gasoline. Plan on 1.5 hours from setup to cleanup for this task.

Tools used
1) Bosch Fuel Filter
2) Assortment of stainless steel hose clamps (two 7/16 and one ½ inch). Did not have to be rated for fuel injection pressure since this is all on the low side of the pump.
3) Extra fuel hose (contingency for splicing)
4) Phillips head and Standard Screw drivers
5) 10 mm socket, extension, and ratchet.
6) Nitrile Gloves (just don’t like gas soaked hands)
7) Safety Glasses
8) Inspection Mirror
9) Golf Tee. (Yes, a wooden Golf Tee.)
10) Garden shear, hand size.
11) Inspection Mirror
12) Drain Pan
13) Jack stand.
14) Hydraulic jack and two 2x4 wood chocks
15) A spring loaded clamp (contingency for pinching hose)

NOTE - I did see one post where a mechanic indicated that fuel pumps occasionally become noisy after replacing the filter, requiring a new $400 pump. This could be caused by changing the filter and having insufficient net positive suction head for the pump, causing it to become vapor bound and run dry. To minimize the air in the fuel filter and avoid vapor binding of the fuel pump, I did this job with a full gas tank, and it was at least 15 minutes between putting the TANK hose line on, and doing the leak check test run. This appeared to be enough time for the filter to soak and develop enough net postive suction head from the tank to avoid vapor binding the fuel pump and cause damage.
 

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Registered
Current 2017 GLE350, 2007 S550, 2002 S430, 1998 ML320 Deceased 74 240D, 92 400E, 97 E420, 13 GLK350
Joined
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1,915 Posts
Discussion Starter #2
This was a job best performed in the driveway, to eliminate the buildup of gas vapors.

Jack the car on driver’s rear side after setting wooden chocks under opposite wheel. Place stand under car – frame member is just inboard of the jack point.

The plastic cover for the fuel filter and pump assembly is on the driver side, just forward of the rear tire. It is held in place with three 10mm plastic nuts, two aft, one forward. Remove and you will see the filter and pump (blue middle in photo) suspended with rubber mounts from the car in a metal carriage. (A side note, my 1997 E420 has metal pan and the fuel carriage is directly mounted to the body. The filter is also a lot less expensive.)

NOTE: Before going further, I pulled the power to the fuel pump. The power connection has locking clamps that needed to be squeezed while pulling off the connection. I chose not to remove the battery power cable, to avoid all of the resets. I did not want the pump starting unexpectedly and run dry. The long cycliner with a middle blue stripe is the fuel pump, with the power lead shown on the left (front) side of the photo.

Loosened the metal carriage holding down the fuel pump and filter with a Phillips screwdriver. No need to remove the screw, just loosened to allow the filter to slide.

Placed the catch container beneath the pump and filter, and put on glove and glasses.

The factory installation of the filter has circlips instead of hose clamps. (The installation precedure in WIS indicates a special plier to take the clamps off and they can be re-clamped using the same tool if they are not damaged. CLIC-R COLIAR PLIERS FOR VW/Audi, BMW, Mercedes.: eBay Motors) However, I simply cut the hose off these clamps and that is where the garden shears came into play.

Three of the four filter connections included hose clamps, one for emissions return was only friction fit. Two things to consider. 1) Look at the length of hose between the pump suction and the filter so determine if you can shorten the hose and the remaining piece will still make the bend radius to the filter. If not, you will have to figure out how to remove the one time use clamp on the pump suction, and replace the line with new. This is the shortest of the hoses and most problematic. 2) Look at the new filter, and of the four connections, identify the one that states ‘TANK’. Then identify that connection on the installed filter.

NOTE: If anyone is replicating the next steps while smoking, please let me know so I can get you nominated for a Darwin Award.

Using the garden shears, cut the hose from the TANK as close the to the filter pipe nipple as possible. It will gush a bit from both the filter and especially the tank. Push the golf tee into the open hose going to the tank. Otherwise, the entire gas tank will drain. Note the locations and cut the other two hoses, pull the filter out of the carriage and let it hang by the emissions connection to drain. (see photo, showing pulled pump power lead, the golf tee plug inserted into left hose, and the new filter loosely set in the carriage with old filter dangling and draining) I chose not to use a clamp on the gas lines because I did not want to deform and potentially crack the hose, compromising its integrity/longevity. However, I had a spring clamp at the ready if the golf tee did not work.
 

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Current 2017 GLE350, 2007 S550, 2002 S430, 1998 ML320 Deceased 74 240D, 92 400E, 97 E420, 13 GLK350
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1,915 Posts
Discussion Starter #3
Ensured correct orientation of new filter and slid into carriage next to the fuel pump. Using appropriate size clamps, restored the hose connections to their correct locations. (The new filter was be labeled for which connection is TANK, PUMP, MOT, so it was hard to screw this up.) The new filter had plastic caps on the four pipe nipples that I did not remove until after it was set in place, and only just before placing a hose connection. This precaution was to prevent dirt/debris from getting into the filter.

The old filter was directly centered in the carriage clamp. With the shortened bend radius of the filter to the pump suction due to cutting off old circlips, this was a different orientation (farther forward). I did not worry about the offset, and simply tightened the carriage clamp after the three hose clamps were installed and the filter found its ‘natural’ position from the spring of the hose lines.

After tightening all clamps, removed the emissions tube from the old filter and installed onto the new filter. The inspection mirror came in handy to check the back side of the clamped connections.

NOTE: Before going further, I restored the power connection to the fuel pump. (See photo of new installation)

At this point, after removing the gas soaked gloves, I leaned in and started the car. It took a few more cranks than usual (since the filter and pump had air in the system), but started within 5 seconds. While the car was running, I did a leak check on the newly installed filter. No leaks, so shut off the car.

Pulled the drain pan out of the way in order to reinstall the body panel that covered the pump and filter. The body panel has to be slid underneath the heat shield and then over the body studs. NOTE – The plastic 10mm nuts can be over torqued and miss-threaded easily. Take care, and don’t try to torque these things. They are designed to grip the body studs and won’t rattle off.

Although I had not experienced any problems with car performance prior to the filter change, I did feel that it was worthwhile. When I made the cut from the tank to the filter some brown swill came out from the filter. Don’t know what it was, but the filter was obviously doing its job. Next filter change out will be easier because the installed hose clamps are now reusable with common screwdriver.
 

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