Issue:
Cunegonde seems to be starting, idling, and running fairly normally...
except a sudden drop from 18-21 MPG to 10 MPG. Running out of gas
repeatedly at 120 miles or less.

Details:
She's acting as if she's continually in cold start enrichment mode -
hot idle sometimes about 200-300rpm higher than usual and no seeking.
Normal idle is about 800 rpm +/- 100.
The start sequence/overheat LED doesn't stop blinking some of the time
- sometimes at cold start for the day, sometimes hot start. But
sometimes the LED stops blinking in the usual 30 seconds before
starting. Sometimes it begins blinking while driving, usually with
temp gauge in low-normal range.
Very occasionally, the temp gauge goes way up and LED blinks while
driving, and then returns to normal, whether or not I turn off the
engine.
Could it be a malfunctioning temp sender? Which one/where is the (blue
plastic-bodied) one not on the thermostat housing?

Resources:
I have the Bentley and a digital multimeter, as well as very full
range of hand tools, ramps, jacks.
I only have spare O2 sensor and thermostat with me.

Actions so far:
I put a tarp under the van while idling to see if there's a fuel line
leak. (I inspect the lines every few months, no fires for Cunegonde!).
No observable leak at any engine speed.
While I am diligently checking every !@#$% connector and wire I can
find in the engine bay, is there another sender or mechanical unit I
can check? Maybe the thermostat?

Timeframe:
I need to have her safely on the road from Seattle to Portland, and
then Grants Pass OR, by next Wednesday. Thanks for any sugggestions,
folks.

--
Bretts

1983 1.9l WBX Ivory Westfalia "Cunegonde"