© 1998-2005 Harald Pietschmann

M-Class fuel pump failure

I filled up in Los Angeles after a fuel pump replacement and added fuel on
I-5 (Chevron on both occasions) drove 450 miles to Georgetown/California. The next morning (June 2000) the vehicle did not want to start anymore. What a surprise after a new pump and some other new goodies (new AAM, new fuse board etc). I immediately talked to an engineer at MBUSI in Tuscaloosa and he recommended the "hammer-treatment" - it worked. My M stated up and I took it to the closest dealer to get yet another fuel pump.

Here is the inside scoop:
The pump failures have very little to do with bad pump design. Pump
failures are only known in the US . MB engineers at MBUSI told me (my
replacement pump had failed one day after installation) that operators
of US gas stations rarely ever stick to the recommended filter change intervalls (to save money) and we ML drivers end up with contaminated gas.

Here is what happens according to MB research: The gas inside some
underground tanks dissolves the protective liner. The liner ends up as a
gooey substance in our tanks. As long as the pump is running there is no
problem. After shutting down the substance hardens inside the pump and
freezes it. Have someone hit the bottom of the tank with a big hammer
while someone else is starting up at the same time and most likely
you'll get the vehicle running again - then drive to the dealer as soon
as possible to get the pump replaced.

Frozen pumps sent for evaluation to Stuttgart did work when they arrived
there - without the presence of gas the "glue" had hardened to a point
that it got brittle and the pumps worked again.

MB is testing an additional filter inside the ML tank to keep the pump
Most newer European cars BMW, Audi etc experience the same fuel pump problems. Here is the fuel pump manufacturer. Why don't Japanese cars suffer from this?
Wolfgang Henke has the answer.