Klause

I have a 2002 e320 wagon with 226,000 miles. My fuel pump died & I replaced it (Pierburg), fuel filter (Mahle & Bosch later) myself. Upon start up after new pump & filter were installed, I noticed the new fuel pump was noticeably louder. Especially when priming. Car drove fine. Over a couple months it increased in noise volume & began to truly sound strained w/ fluctuations in pitch & what sounded like cavitation. Never ran poorly & started ok. Out of fear of being stranded, I replaced the pump w/ another new Pierburg thinking I had a bad unit. Upon starting post install, the pump sounded worse than the prior pump. Big strained sound on prime, wouldn’t start. I replaced the fuel filter with a Bosch, thinking maybe that was the problem LOL. No luck, car would turn over but not start. Had it towed to a trusted mechanic, he replaced fuel relay, crank position sensor, new Pierburg pump, new Bosch filter, cleaned out gas tank & internal tank fuel strainer (it looked clean). He was able to get the car to idle 15minutes & it burned out the fuel pump. After checking fuel lines, he found the line directly from the pump to the filter was clogged. Replaced the fuel line & it runs well. BUT, the new fuel pump still sounds very loud, strained, changes pitch, makes a popping sounds etc. I don’t trust this pump working so hard & fear being stranded. Mechanic feels car runs well, pump is just noisy & clogged fuel line was the problem. He has been solid with every complicated repair I’ve had w/ my euro cars. I’m stumped. Thinking about doing an aftermarket fuel filter with a simple in & exit port & bypass the 4 port OEM filter with all its return lines etc. Fuel system diagrams lead me to think that is not realistic & I’ll have issues with no regulation of pressure (OE filter has internal regulator), excess stock return lines etc. Should I replace the rest of the 3 fuel lines that come off of the OE filter? I’m Open to suggestions & can’t seem to find any established issues of this in w210 e320’s. Appreciate your time!!! Thanks

Plutoe

the pump or pumps you changed were they MB or junk yard

Klause

All brand new Pierburg, Bosch, Mahle, Mann etc.

Klause

Appreciate the help.

brauhaus313

Have you checked fuel pressure at the rail? Just to get things straight, you're now on your third Pierburg pump after your second Pierburg burned out? Are you sure the Pierburgs aren't remanufactured units, even though labeled as "new"? From what I can see, even Mercedes only sells remanufactured units now, and that's what I would go for as I highly doubt Mercedes could get away with installing fuel pumps that buzz or whine out of the box.

I had fuel pump noise issues (cavitation sound/buzzing) after I installed an aftermarket Bosch fuel filter as preventative maintenance. I had no issues with my fuel pump prior. I suggest installing new OE parts back on your car. Mahle and Bosch are OEMs, but that doesn't mean the aftermarket parts are to OE standards or that they were the manufacturers of your specific OE parts. For example, FCP Euro lists Mann, Bosch, Mahle, and Hengst all as OEM, yet the OE Mercedes filter has the Knecht logo imprinted on it. Knecht is part of the Mahle umbrella group, but that doesn't mean Knecht filters are the same as Mahle. The Bosch filter listed as "OEM" shows "Made in Spain" on the pictured filter, but the country of manufacture listed in the description is South Africa. It's all become a clusterf$*& as most brands that we previously could kneejerk consider quality and reliable have consolidated/conglomerated under various umbrellas that then turn around and outsource to other regions all over the world.

For certain parts OEM is fine. For critical parts, go OE. I own 2 M113 cars that use the same fuel filter as the one in your M112 E320. Had the same fuel pump noise when I replaced with the Bosch filter in one car, and zero problems when I replaced with an OE Mercedes filter in the other car. If you look on FCP Euro, the OE filter is actually about the same price or cheaper than the "OEM" parts.