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Thanks Marty D., This is what I learned from the thread you pointed me to:
The engine control module continuously checks the voltage value of the fuel temp sensor and compares it with the threshold values.
The P0180 fault is recorded when:
<0.2 V longer than 2 seconds
>4.7 V longer than 2 seconds
Attached is a chart of the specified temp and voltage values (Green line)
I extrapolated the line up to 100 deg C (orange line)
The High and Low limits are shown in Red and Blue
So, even when the fuel is delivered hot by the veggie oil conversion kit, it shouldn’t exceed the high limit. (Veggie is heated by the coolant and my car rarely exceeds 80 deg C)
Therefore my fuel temp sensor is bad.
OK, that’s a relatively easy fix. But why does the engine care what the fuel temperature is anyway? I know the stock engine has a fuel heat exchanger that works when the temp is very cold and the diesel has the potential to gel. I’m not sure how the ’98 works, but my 1986 190D preheater is controlled by a mechanical thermostat. If the ‘98 is the same, it wouldn’t need an electronic fuel temp input signal. So what's it for?
Thanks,
Paul
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1998 E300D 1-tank Elsbett Veggie system
1986 190D 2-tank Veggie system -Sold
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