Does anybody have any kind of schematic that will show me exactly how
fuel system works on a Mercedes 300D?
My plans are to convert mine to run on biodiesel. I am torn between
using a inline, 12V electric fuel heater vs. a coolant heat exchanger
in the aux. tank.
I would really like to retrofit this car to have a high output GM
alternator anyway. Therefore, a 12V heater drawing about 15 or 20 amps
shouldn't be a problem. This way, I could save a lot of coolant hose to
the trunk, I could use biodiesel before the engine coolant/biodiesel is
up to temperature, and I could regulate the temperature of the
biodiesel easier with pulse width modulation control (cycle the 12V
heater on and off every few seconds to achieve the desired biodiesel
This would probably require a small accumulator tank with an RTD or
thermistor for fuel temperature feedback. The tank should prevent an
unstable situation with the 12V heater. (i.e. the heater will not cycle
on and off too quickly and ruin the relay that supplies power to the
If this works the way I would like it to, then I will surely use a PIC
microcontroller and programming to:
-automatically run the tank selector valves
-take feedback from the biodiesel temperature
-turn the 12V heater on or off based on that temperature feedback
-automatically switch back to regular diesel when biodiesel tank gets
-automatically switch back to regular diesel when the key is turned off
and allow the engine to run for a few seconds. This will allow the
biodiesel to purge out of the fuel system. This way the engine can't be
shut off on biodiesel. (My engine is turned off with an electronically
actuated, pneumatic valve due to my previous remote start / keyless
I want to have a switch with 3 positions; Biodiesel, diesel, and auto.
Where "auto" will automatically select bio or diesel based on system
feedback. Maybe a couple LED's... to show which take is active.
Has anyone used only an electric heater to heat the Bio fuel? If so, it
would be nice if you could share a couple pictures and a description.
1984 Mercedes 300D Turbodiesel - 280K today.
In case you can't tell, I am one of those crazy EE's :)
Penn State all the way...