98 E300 what does the fuel temp sensor do?

[veggiediesel]

Vehicle: 1998 E300D, 95,000 miles

Problem 1: Check engine light came on yesterday, showing code P0180 "Fuel Temperature Sensor A Circuit Malfunction"

Problem 2: Delivery valves on injection pump are leaking. I have crush washers and a full set of Viton o-rings for the fuel system and am ready to do the repair, but want to be prepared to tackle all problems once the intake manifold is off.

Problem 3: Engine runs rough when vehicle is not under load, but not at idle. For example, when coasting towards a red light, but before the engine cuts back to idle speed. Engine is silky smooth at idle and under load.

Question: Are all 3 problems related?

Important details:

About a thousand miles ago I installed an Elsbett veggie oil system on the vehicle. This is a one tank system with a coolant/fuel heat exchanger located in the engine compartment immediately before the OEM fuel heat exchanger, fuel filter, fuel shut off valve, lift pump, injection pump, and so on. The conversion also utilizes special injector nozzles and longer glow plugs.

Regarding problem 1: Since the Elsbett system supplies hot fuel (veggie) to the fuel system, is this confusing the fuel temp sensor and causing it to think it's malfunctioning? Does a constant supply of hot fuel make the car think something is wrong? What does the car do with the fuel temp info anyhow?

Thanks,
Paul


Here are some threads that I found helpful on this site:

Error P0180:
http://www.peachparts.com/shopforum/showthread.php?t=40962

Replacing fuel lines and seals:
http://www.peachparts.com/shopforum/showthread.php?t=105291&highlight=fuel+manifold+ring
go to post #8 by Rick Miley