I just learned something interesting from my new-to-me FSM "Service Manual, Diesel Engines 602, 603." Turns out that there is something called a "splash pot" at the bottom of the fuel tank; it is mentioned in one other thread here but otherwise not discussed. I am interested in how it would affect algae and other crud that has been accused of causing problems by clogging up the screen in the fuel tank. [I have personally never had such a problem.]

In the picture below, the "splash pot" is shown at the bottom of the fuel tank with the screen guarding the pickup line in the center. The purpose of the splash pot is to keep the pickup line from sucking air when the tank is low and you do some hard cornering or park at a severe lean.

I'm interested in the detail picture that shows how the return line goes into the splash pot. This means that the splash pot has a continual flow of fuel that has gone through the fuel filters and is therefore clean (because we all change our filters religiously, right?). Would this continual flow of clean fuel into the splash pot keep the dirt and other crud out?

This splash pot would seem to apply (based on the 1990 publication date of this manual) to 1986-90 W201, W124, and W126 with NA and turbo diesel engines. What about our 123 diesels and older Benz diesels? Do they have "splash pots?" Are they more susceptible to algae and crud if they don't?

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Almost like a reserve hmm...

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The "splash pot" is not designed to, and doesn't hold fuel with the engine (pump) off. It will drain out through the siphon port by the return nozzle.

Further, the siphon port by the return nozzle is open to fuel in the bottom of the fuel tank, this is how the jet of fuel from the return nozzle can scavenge additional fuel from the tank bottom when it is operating. Because of this, it is able to be contaminated with anything in the tank.

Most common fuel contaminants require the water on top of the fuel and seldom cause any problem (other than sediment) below the fuel level. Condensation on the tank lining happens mostly with metal tanks, less so with plastic tanks (because the plastic doesn't conduct heat into the cold fuel and become cold enough for condensation) and is the primary location for "algae" growth. Keep good fuel in the tank, treat it if there is a problem or just for good insurance, and keep the tank full whenever un-used.

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Gone to the dark side

- Jeff